WO2012010993A2 - Electric motor with varying torque efficiency profile - Google Patents

Electric motor with varying torque efficiency profile Download PDF

Info

Publication number
WO2012010993A2
WO2012010993A2 PCT/IB2011/052664 IB2011052664W WO2012010993A2 WO 2012010993 A2 WO2012010993 A2 WO 2012010993A2 IB 2011052664 W IB2011052664 W IB 2011052664W WO 2012010993 A2 WO2012010993 A2 WO 2012010993A2
Authority
WO
WIPO (PCT)
Prior art keywords
electric motor
sub
control device
coil
torque
Prior art date
Application number
PCT/IB2011/052664
Other languages
French (fr)
Other versions
WO2012010993A3 (en
Inventor
Gerard Boast
Geoffrey Owen
Anthony Wearing
Simon Brockway
Dragica Kostic Perovic
Original Assignee
Protean Electric Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Protean Electric Limited filed Critical Protean Electric Limited
Publication of WO2012010993A2 publication Critical patent/WO2012010993A2/en
Publication of WO2012010993A3 publication Critical patent/WO2012010993A3/en

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/16—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the circuit arrangement or by the kind of wiring
    • H02P25/22—Multiple windings; Windings for more than three phases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K7/00—Disposition of motor in, or adjacent to, traction wheel
    • B60K7/0007—Disposition of motor in, or adjacent to, traction wheel the motor being electric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/007—Physical arrangements or structures of drive train converters specially adapted for the propulsion motors of electric vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/02—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles characterised by the form of the current used in the control circuit
    • B60L15/025—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles characterised by the form of the current used in the control circuit using field orientation; Vector control; Direct Torque Control [DTC]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
    • B60L15/2045—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed for optimising the use of energy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L50/00—Electric propulsion with power supplied within the vehicle
    • B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
    • H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices
    • H02K29/08—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices using magnetic effect devices, e.g. Hall-plates, magneto-resistors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P5/00—Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors
    • H02P5/74—Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors controlling two or more ac dynamo-electric motors
    • H02P5/747—Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors controlling two or more ac dynamo-electric motors mechanically coupled by gearing
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/08—Arrangements for controlling the speed or torque of a single motor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/08—Arrangements for controlling the speed or torque of a single motor
    • H02P6/085—Arrangements for controlling the speed or torque of a single motor in a bridge configuration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K17/00—Arrangement or mounting of transmissions in vehicles
    • B60K17/34—Arrangement or mounting of transmissions in vehicles for driving both front and rear wheels, e.g. four wheel drive vehicles
    • B60K17/356—Arrangement or mounting of transmissions in vehicles for driving both front and rear wheels, e.g. four wheel drive vehicles having fluid or electric motor, for driving one or more wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K7/00—Disposition of motor in, or adjacent to, traction wheel
    • B60K2007/0038—Disposition of motor in, or adjacent to, traction wheel the motor moving together with the wheel axle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K7/00—Disposition of motor in, or adjacent to, traction wheel
    • B60K2007/0092—Disposition of motor in, or adjacent to, traction wheel the motor axle being coaxial to the wheel axle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2220/00—Electrical machine types; Structures or applications thereof
    • B60L2220/10—Electrical machine types
    • B60L2220/14—Synchronous machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2220/00—Electrical machine types; Structures or applications thereof
    • B60L2220/40—Electrical machine applications
    • B60L2220/44—Wheel Hub motors, i.e. integrated in the wheel hub
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2270/00—Problem solutions or means not otherwise provided for
    • B60L2270/10—Emission reduction
    • B60L2270/14—Emission reduction of noise
    • B60L2270/142—Emission reduction of noise acoustic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2270/00—Problem solutions or means not otherwise provided for
    • B60L2270/10—Emission reduction
    • B60L2270/14—Emission reduction of noise
    • B60L2270/145—Structure borne vibrations
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
    • H02P2207/07—Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to rotor and stator windings
    • H02P2207/073—Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to rotor and stator windings wherein only one converter is used, the other windings being supplied without converter, e.g. doubly-fed induction machines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/64—Electric machine technologies in electromobility
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

Definitions

  • the present invention relates to an electric motor and in particular an in-wheel electric motor.
  • Electric motor systems typically include an electric motor and a control unit arranged to control the power of the electric motor, which may be configured as either a rotary or linear electric motor.
  • Examples of known types of electric motor include the induction motor, synchronous brushless permanent magnet motor and switched reluctance motor.
  • three phase electric motors are the most common kind of electric motor available.
  • a three phase electric motor typically includes three coil sets, where each coil set is arranged to generate a magnetic field associated with one of the three phases of an alternating voltage. To increase the number of magnetic poles formed within an electric motor, each coil set will typically have a number of coil sub-sets that are distributed around the periphery of the electric motor, which are driven to produce a rotating magnetic field.
  • Fig. 1 shows a typical three phase electric motor 10 having three coils 14, 16, 18. Each coil consists of four coil sub-sets that are connected in series. Accordingly, for a given coil set the magnetic field generated by the respective coil sub-sets will have a common phase .
  • the three coil sets of a three phase electric motor are typically configured in either a delta or wye configuration, where a delta configuration is illustrated in Fig. 2 and a wye configuration is illustrated in Fig. 3.
  • a control unit for a three phase electric motor having a DC power supply will typically include a three phase bridge inverter that generates a three phase voltage supply for driving the electric motor. Each of the respective voltage phases is applied to a respective coil set of the electric motor .
  • a three phase bridge inverter includes a number of switching devices, for example power electronic switches such as Insulated Gate Bipolar Transistor (IGBT) switches.
  • IGBT Insulated Gate Bipolar Transistor
  • an electric motor will typically have motor characteristics that have different values at different speed or torque settings.
  • the torque efficiency of an electric motor at one torque value will typically be different to the torque efficiency of the electric motor at a different torque value, where the set of torque efficiency values of an electric motor are normally illustrated in a torque efficiency profile, which is used to map the efficiency of an electric motor at a range of motor speed/torque ratios.
  • an electric motor will inevitably have greater efficiency at one speed/torque ratio compared to another speed/torque ratio.
  • an electric motor can be designed to have optimum torque efficiency in this range.
  • an electric motor that is expected to operate in a wide range of speed/torque ranges for example an electric motor designed to drive a vehicle, it will be inevitable that the electric motor will be required at times to operate in a relatively inefficient speed/torque range.
  • an electric motor according to the accompanying claims .
  • the present invention allows an electric motor to have a number of sub motors that can operate independently of each other, where each of the sub motors has a set of values for a motor characteristic that are different to at least one other sub motor.
  • the motor characteristic could be torque/speed efficiency.
  • each sub motor can be operated independently with the torque demand for each sub motor being selected based on the torque/speed efficiency map associated with each sub motor, thereby selectively providing a required overall torque/speed efficiency for the electric motor and consequently allowing an electric motor to operate in an efficient speed torque range for a wide range of torque demands.
  • the current flow in the coil sub-sets of one coil set is independent of the current flow in the coil sub ⁇ sets of another coil set (i.e. the respective coil sub-sets are not connected in series) . Consequently, the coils of each coil sub-set can have a larger number of turns than for an equivalent motor in which all respective coil sub-sets are connected in series. The increased number of turns in each coil increases the overall inductance of the motor. This means that lower currents can be used in the coils of each coil sub-set, which leads to fewer heat dissipation problems, and which allows smaller switching devices to be used. The use of smaller switching devices in turn allows for faster switching speeds and lower switching losses.
  • the coils of a coil sub-set are arranged to form a multi-phase electric motor (i.e. forms a logical sub- motor) the coils of a coil sub-set can be configured either in a delta or wye configuration as best fits the specific electric motor requirements.
  • the respective control devices otherwise known as drive units, include an inverter having a plurality of switches for applying a pulse width modulated (PWM) voltage to the plurality of respective coil sub-sets, which is used to control current within the coils of the coil sub-set.
  • PWM control of the currents in the motor coils can be enhanced due to the increased number of turns that can be included in the coils. As smaller switching device can be used, significant savings in cost, weight and heat dissipation can be made.
  • control devices can be housed within a casing of the motor.
  • the control devices can be located adjacent the coil sub-sets of the respective coil set within the motor thereby simplifying termination of the coil windings.
  • the casing of the motor can include one or more apertures dimensioned such that the control devices can be accessed one at a time, depending on the orientation of the rotor/casing and the control devices.
  • a common control device can be provided to coordinate the operation of the plurality of control devices, thereby allowing the independent sub-motors of the electric motor to be centrally controlled. Accordingly, the common control device can be operable to selectively disable one or more of the control devices to allow fractional power operation or to adjust the power of one sub-motor to compensate for a fault in another sub-motor.
  • An electric motor having parallel sub-motors reduces current per coil set compared to an electric motor having serially coupled coil sets. Further by having the control devices for each sub motor located within the electric motor assembly, with associated capacitance also located within the electric motor assembly, reduces the capacitance requirements for the electric motor.
  • Figure 1 schematically shows an example of three phase motor arrangement
  • Figure 2 illustrates a three phase motor delta coil wiring arrangement
  • Figure 3 illustrates a three phase motor wye coil wiring arrangement
  • Figure 4 illustrates an exploded view of a motor embodying the present invention
  • Figure 5 is an exploded view of the motor of Figure 3 from an alternative angle
  • Figure 6 schematically shows an example arrangement of coil sets for an electric motor according to an embodiment of the present invention
  • Figure 7 illustrates a first torque efficiency map associated with a first subset of sub motors
  • Figure 8 illustrates a second torque efficiency map associated with a second subset of sub motors
  • Figure 9 schematically illustrates the coils sub-sets of an electric motor according to an embodiment of the present invention that are configured in a wye configuration
  • Figure 10 schematically illustrates the coils sub-sets of an electric motor according to an embodiment of the present invention that are configured in a delta configuration
  • Figure 11 schematically shows an example of a control device in accordance with an embodiment of the present invention
  • Figure 12 is a circuit diagram of the switching arrangement.
  • the embodiment of the invention described is an electric motor for use in a wheel of a vehicle.
  • the motor is of the type having a set of coils being part of the stator for attachment to a vehicle, radially surrounded by a rotor carrying a set of magnets for attachment to a wheel.
  • the various aspects of the invention are equally applicable to an electric generator having the same arrangement.
  • the definition of electric motor is intended to include electric generator.
  • some of the aspects of the invention are applicable to an arrangement having the rotor centrally mounted within radially surrounding coils.
  • the assembly comprises a stator 252 comprising a rear portion 230 forming a first part of the housing of the assembly, and a heat sink and drive arrangement 231 comprising multiple coils and electronics to drive the coils as well as a heat sink.
  • the coil drive arrangement 231 is fixed to the rear portion 230 to form the stator 252 which may then be fixed to a vehicle and does not rotate during use.
  • the coils themselves are formed on tooth laminations which together with the drive arrangement 231 and rear portion 230 form the stator 252.
  • capacitor circuit boards for providing capacitance between the electric motor and the voltage supply to reduce voltage line drop.
  • a rotor 240 comprises a front portion 220 and a cylindrical portion 221 forming a cover, which substantially surrounds the stator 252.
  • the rotor includes a plurality of magnets 242 arranged around the inside of the cylindrical portion 221. The magnets are thus in close proximity to the coils on the assembly 231 so that magnetic fields generated by the coils in the assembly 231 generate a force on the magnets 242 arranged around the inside of the cylindrical portion 221 of the rotor 240 thereby causing the rotor 240 to rotate .
  • the rotor 240 is attached to the stator 252 by a bearing block 223.
  • the bearing block 223 can be a standard bearing block as would be used in a vehicle to which this motor assembly is to be fitted.
  • the bearing block comprises two parts, a first part fixed to the stator and a second part fixed to the rotor.
  • the bearing block is fixed to a central portion 233 of the wall 230 of the stator 252 and also to a central portion 225 of the housing wall 220 of the rotor 240.
  • the rotor 240 is thus rotationally fixed to the vehicle with which it is to be used via the bearing block 223 at the central portion 225 of the rotor 240.
  • This has a significant advantage in that a wheel rim and tyre can then be fixed to the rotor 240 at the central portion 225 using the normal wheel bolts to fix the wheel rim to the central portion of the rotor and consequently firmly onto the rotatable side of the bearing block 223.
  • the wheel bolts may be fitted through the central portion 225 of the rotor through into the bearing block itself.
  • a first advantage of this arrangement is that the whole assembly may be simply retrofitted to an existing vehicle by removing the wheel, bearing block and any other components such as the braking arrangement. The existing bearing block can then fitted inside the assembly and the whole arrangement fitted to the vehicle on the stator side and the normal rim and wheel fitted to the rotor so that the rim and wheel surrounds the whole motor assembly. Accordingly, retrofitting to existing vehicles becomes very simple.
  • a second advantage is that there are no forces for supporting the vehicle on the outside of the rotor 240, particularly on the circumferential wall 221 carrying the magnets on the inside circumference.
  • FIG. 5 shows an exploded view of the same assembly as Figure 4 from the opposite side showing the stator 252 comprising the rear stator wall 230 and coil and electronics assembly 231.
  • the rotor 240 comprises the outer rotor wall 220 and circumferential wall 221 within which magnets 242 are circumferentially arranged.
  • the stator 252 is connected to the rotor 240 via the bearing block 223 at the central portions of the rotor and stator walls .
  • control devices 80 otherwise known as motor drive circuits, which, as described below, includes an inverter.
  • a V shaped seal 350 is provided between the circumferential wall 221 of the rotor and the outer edge of the stator housing 230.
  • the magnetic ring 227 comprising a commutation focusing ring and a plurality of magnets is provided for the purpose of indicating the position of the rotor with respect to the stator to a series of sensors arranged on the control devices 80 of the stator 252.
  • FIG. 6 schematically shows an example of an electric motor 40 in accordance with an embodiment of this invention.
  • the motor is generally circular.
  • embodiments of this invention can employ other topologies.
  • a linear arrangement of coils for producing linear movement is envisaged.
  • the motor 40 in this example includes eight coil sets 60 with each coil set 60 having three coil sub-sets 61, 62, 63 that are coupled to a respective control device 64, where each control device 64 and respective coil sub-sets form a three phase logical or sub electric motor that can be controlled independently of the other sub motors.
  • the control devices 64 drive their respective sub motor with a three phase voltage supply, thereby allowing the respective coil sub-sets to generate a rotating magnetic field.
  • each coil set 60 describes each coil set 60 as having three coil sub-sets 61, 62, 63, the present invention is not limited by this and it would be appreciated that each coil set 60 could have two or more coil sub-sets.
  • the present embodiment describes an electric motor having eight coil sets 60 (i.e. eight sub motors) the motor could have two or more coil sets with associated control devices (i.e. two or more sub motors) .
  • the motor 40 can include a rotor (not shown in Figure 6) positioned in the centre of the circle defined by the positioning of the various coils of the motor, thereby to allow rotation of the rotor within the rotating magnetic field produced by the coils.
  • the rotor is arranged around the coils as previously disclosed in Figures 4 and 5.
  • the rotor may typically comprise one or more permanent magnets arranged to rotate such that their poles sweep across the ends of the coils of the motor 40. Appropriate switching of currents in the coils of the coil sub-sets 61, 62, 63 allows synchronized attraction and repulsion of the poles of the permanent magnet of the rotor to produce the rotating action of the motor 40.
  • Figure 6 is highly schematic and, in practice, the coil sub-sets will be arranged at the outer periphery of the stator with the rotor magnets surrounding the coils.
  • each control device includes a three phase bridge inverter which, as is well known to a person skilled in the art, contains six switches.
  • the three phase bridge inverter is coupled to the three subset coils of a coil set
  • the motor includes eight three phase sub-motors, where each three phase sub-motor includes a control device 64 coupled to the three sub-set coils of a coil set 60.
  • Each three phase bridge inverter is arranged to provide PWM voltage control across the respective coil sub-sets 61, 62, 63 to provide a required torque for the respective sub- motors .
  • the three phase bridge switches of a control device 64 are arranged to apply a single voltage phase across each of the coil sub-sets 61, 62, 63.
  • Torque otherwise known as moment of force, is a measure of the turning force on the rotor and is a product of the force on the rotor and rotor radius .
  • torque is typically proportional to current flow in the electric motors coil windings.
  • Efficiency of a motor is defined by the ratio of output mechanical power to input electrical power, where a torque/speed efficiency map defines the efficiency of an electric motor over a range of speed and torque values.
  • Torque/speed efficiency of an electric motor can vary as a result of many features within the motor. For example, the number of coil windings formed on tooth laminations, the diameter of the coils used to form the coil windings on the tooth laminations, the shape of the stator teeth and/or the air gap between the end of the tooth laminations and the rotor magnets, and the voltage applied across the coils.
  • At least two of the sub motors are arranged to have a torque/speed efficiency map that have different sets of values.
  • the set of torque/speed efficiency values can be varied between any number of the different sub motors .
  • the present invention is not limited to different sets of torque/speed efficiency values, other motor characteristics can be varied between different sub motors, either in addition to torque/speed efficiency values or as an alternative.
  • any suitable sub motor design feature can be changed.
  • any one or more of the following features can be varied between different sub motors: the number of coil windings formed on tooth laminations, the diameter of the coils used to form the coil windings on the tooth laminations, the shape of the stator teeth and/or the air gap between the end of the tooth laminations and the rotor magnets, and the voltage applied across the coils.
  • the respective sub motors can be driven to generate a predetermined torque/speed efficiency map.
  • the design criteria for determining the torque/speed efficiency map values for any one of the sub motors will typically be determined based on the intended use of the electric motor.
  • the electric motor may be designed to have four sub motors with a torque/speed efficiency map that is substantially the same as a first torque/speed efficiency map, while the other four sub motors are arranged to have a torque/speed efficiency map that is substantially the same as a second torque/speed efficiency map.
  • the electric motor can be designed to have any arrangement of torque/speed efficiency map/sub motor configuration, for example three of the sub motors could have substantially the same torque/speed efficiency map with the other five sub motors having a different torque/speed efficiency map.
  • all of the sub motors could be arranged to have different torque/speed efficiency maps.
  • the torque/speed efficiency map for a first set of sub motors can be selected to be different to the torque/speed efficiency map for a second set of sub motors (i.e. a first set of sub motors can be regarded as being equivalent to a first sub motor with a predetermined torque/speed efficiency map with a second set of sub motors being regarded as being equivalent to a second sub motor with a predetermined torque/speed efficiency map) .
  • any combination of sub motor/torque/speed efficiency map configuration could be adopted based on the design needs of the electric motor.
  • the present embodiment is based on driving an electric motor having a plurality of sub motors while maximizing torque/speed efficiency
  • the principle can be applied to regeneration of the electric motor (i.e. treating the electric motor as a generator) , while minimizing electric motor losses.
  • each in wheel electric motor For a vehicle primarily intended to be driven in either an urban environment, which typically involves low speeds and high torque, or a highway environment, which typically requires high speed and low torques, four of the eight sub motors for each in wheel electric motor are arranged to have substantially the same torque/speed efficiency map, which when operated together has a torque/speed efficiency map corresponding to the torque/speed efficiency values illustrated in Figure 7.
  • the second set of the eight sub motors are arranged to have substantially the same torque/speed efficiency map, which when operated together has a torque/speed efficiency map corresponding to the torque/speed efficiency values illustrated in Figure 8.
  • Each sub motor has a maximum torque in the region of 200Nm.
  • the first torque/speed efficiency map is configured to have higher torque/speed efficiency values at lower speeds, as typically encountered when driving in an urban environment.
  • the second torque/speed efficiency map is configured to have higher torque/speed efficiency values at higher speeds, as typically encountered when driving on the highway.
  • a table is stored in memory, preferably within the in wheel control device, that defines the amount of torque contribution provided by each set of sub motors, where total torque T to tai is a sum of torque provided by the first set of sub motors T A and the second set of sub motors T B .
  • the table lists the percentage contribution of the first set of sub motors and second set of sub motors over the range of available torque values and motor speeds, which for the present embodiment would correspond to a range of 0 to 1600Nm torque and 0 to 1200rpm.
  • the table can be created using any suitable means, for example by populating the table with percentage contributions to provide optimum torque/speed efficiency at specified torque/speed points.
  • the contribution provided by the first set of sub motors would be 100%.
  • the torque contribution provided by the second set of sub motors would be 0%.
  • the torque contribution is determined by the electric current generated in the coil windings associated with the respective sub motors.
  • the torque contribution provided by the second set of sub motors would be 100%.
  • the torque contribution provided by the first set of sub motors would be 0%.
  • both sets of sub motors will provide a torque contribution, particularly if the total torque requirement exceeds that available per set of sub motors.
  • a possible scenario would be for 500Nm to be provided by the first set of sub motors, operating with between 88% and 90% torque/speed efficiency, and 200Nm would be provided by the second set of sub motors operating at around 90% torque/speed efficiency. Accordingly, for a required torque value the current flow in the coil windings of the respective sub motors is selected to provide a predetermined torque efficiency for the electric motor.
  • the required torque value for the electric motor may be fixed but the current selected to flow through the coil windings of the respective sub motors is varied/selected to provide a predetermined torque efficiency for the electric motor based on a sum of the torque efficiencies of the respective sub motors and their contribution to the overall torque generated by the electric motor .
  • the present embodiment utilizes a table to define the ratio of torque generated by the respective sub motors at a required speed
  • the ratio of torque generated by the respective sub motors at a required speed can also be determined by other means, for example using an algorithm.
  • some form of control loop could be implemented in which the contribution of torque provided by different sub motors is varied using a feedback loop to provide an optimized torque efficiency for an electric motor for a given overall torque value.
  • the means for determining the ratio of torque generated by the respective sub motors can also be configured to accommodate changes in temperature of the respective sub motors. For example, to avoid overheating of a sub motor, once the temperature of a sub motor has exceeded a threshold value a different ratio of torque generation may be adopted to avoid overheating of a sub motor .
  • Figure 9 illustrates the electric motor shown in Figure 6, where each control device bridge inverter is coupled to their respective coil sub-sets to form a wye configuration.
  • Figure 10 illustrates the electric motor shown in Figure 6, where each control device bridge inverter is coupled to their respective coil sub-sets to form a delta configuration .
  • one set of sub motors can be coupled in a wye configuration while the other set of sub motors can be coupled in a delta configuration.
  • Figure 11 shows an example of a control device 80 in accordance with an embodiment of this invention.
  • the control device 80 includes a first circuit board 83 and a second circuit board 82.
  • the second board 82 is arranged to overlay the first circuit board 83, as illustrated in Figure 11.
  • the first circuit board 83 includes a plurality of switches that are arranged to apply an alternating voltage across the respective coil sub-sets.
  • the switches can include semiconductor devices such as MOSFETs or IGBTs.
  • the switches comprise IGBT switches.
  • the plurality of switches are configured to form an n-phase bridge circuit. Accordingly, as is well known to a person skilled in the art, the number of switches will depend upon the number of voltage phases to be applied to the respective sub motors.
  • the first circuit board 83 of the respective control devices include six switches. Although the current design shows each sub motor having a three phase construction, the sub motors can be constructed to have two or more phases.
  • the wires (e.g. copper wires) of the coil sub-sets can be connected directly to the switching devices as appropriate.
  • the second circuit board 82 includes a number of electrical components for controlling the operation of the switches mounted on the first circuit board 83. Examples of electrical components mounted on the second circuit board 82 include control logic for controlling the operation of the switches for providing PWM voltage control and interface components, such as a CAN interface chip, for allowing the control device 80 to communicate with devices external to the control device 80, such as other control devices 80 or a master controller. Typically the second control board 82 will communicate over the interface to receive torque demand requests and to transmit status information.
  • the second circuit board 82 is arranged to be mounted on top of the first circuit board 83, where the first circuit board 83 and the second circuit board include means for being mounted within the motor 40, for example, adjacent to the coil sub-set which they control, directly to a cooling plate.
  • these means include apertures 84 through which screws or suchlike can pass.
  • the first circuit board 83 and the second circuit board 82 are substantially wedge- shaped. This shape allows multiple control devices 80 to be located adjacent each other within the motor, forming a fanlike arrangement. By separating the control logic from the switches this has the advantage of thermally isolating the control logic from the switches while also minimizing the impact of any electrical noise generated by the switches.
  • a sensor that can be used for determining the position of the rotor 240, for example a hall sensor that is arranged to generate an electrical signal dependent upon the relative position of the focusing ring and magnets 227 that is mounted on the rotor 240.
  • a sensor that can be used for determining the position of the rotor 240, for example a hall sensor that is arranged to generate an electrical signal dependent upon the relative position of the focusing ring and magnets 227 that is mounted on the rotor 240.
  • To determine the direction that the rotor is turning in the circuit boards preferably have two sensors that are offset by a predetermined angle so that the changes in signal from each of the sensors can be analyzed to determine both the relative position of the rotor 240 and the direction of rotation of the rotor.
  • each circuit board has their own set of position sensors. However, a single set of position sensors could be used.
  • Figure 12 illustrates six switches of the first circuit board arranged in an 3 phase bridge configuration that are coupled to the coil sub-sets of a coil set that are placed in a wye configuration.
  • the six semiconductor switches are connected to a voltage supply, for example 300 volts, and to ground. Pairs of the respective coil sub-sets are connected between two legs of the bridge circuit. Simplistically, to operate the motor and supply a voltage in one direction, the switches are operated in pairs, one in the top half of the bridge and one from a different leg in the bottom half of the bridge. Each switch carries the output current for one third of the time.
  • the timing and polarity of the current flow in the coil is changed to cause the resulting forces in the opposite direction.
  • the technique of pulse width modulating is used to pulse width modulate the signal applied to the gate of the semiconductor switches to control the voltage applied to the coils, where the PWM voltage is determined based uon a received torque demand request. The PWM voltage in turn determines the coil current and hence the produced torque.
  • a common control device can be located within the in-wheel electric motor for monitoring and adjusting the operation of the respective sub motors to balance the operation of the respective sub motors .
  • the balancing and synchronization of the respective sub motors can be performed by one or more of the sub motor control devices 80, where the in-wheel electric motor control devices 80 communicate between each other via the communication bus.
  • each motor incorporates all the intelligence needed to manage its actions.
  • Each motor understands its position on the vehicle and controls its actions accordingly.
  • each motor is further provided with information regarding the other motors such as the speed, torque and status and are based on each motor' s knowledge of its position on the vehicle and the state and status of the other motors it can determine the optimum level of torque that it should apply for a given demanded torque. Even without this other information, though, the motor can continue to respond to a demanded torque.
  • control signals such as power up/power down control signals can also be sent/received to/from a master controller that is arranged to control the overall operation of the vehicle to which the respective in-wheel electric motors are mounted.
  • the control signals are communicated to the respective control devices 80 for an in-wheel electric motor either directly or indirectly via a common control device.
  • the control signals will typically be communicated via the communication bus, for example a CAN bus.
  • the signals can be communicated by any suitable means.
  • the control signals can also include signals for adj usting/defining the voltage pulses applied by the control device 80 to the coils of its associated coil sub-set for powering the motor and thereby adjust the torque demand for the in-wheel electric motor.
  • each electrical signal generated to drive the different coil sub-sets, within a given coil set have a different phase angle.
  • Each electrical signal generated by different circuit boards has substantially the same phase angle as corresponding electrical signals generated by other circuit boards. For example, for a three phase motor, where each sub motor includes a coil set having three coil sub ⁇ sets, each sub motor will generate an electrical signal having a first phase angle that is substantially the same for each sub motor. Similarly, each sub motor in a three phase motor will also generate electrical signals having a second and third phase angle, where the second and third phase angles are substantially the same between the sub motors .
  • phase angle and voltage envelope for each of the different electrical signals are generated by the respective circuit boards using PWM voltage control, where the voltage envelope and phase angle of the electrical signals is determined by the modulating voltage pulses.
  • the PWM voltage signals generated by each sub motor for electrical signals having a voltage envelope with substantially the same phase angle are offset with respect to each other. That is to say, even though the voltage envelope for different signals generated by different sub motors is substantially the same, the PWM signal used to generate these voltage signals are offset with respect to each other.
  • PWM counters for each of the different sub motors are synchronized and an offset synchronous signal is generated for the counters on the different circuit boards, where the offset synchronous signal is different for each circuit board (i.e. for each sub motor) .
  • This has the effect of phase shifting the PWM voltage for each corresponding electric phase signal provided by each circuit board. Accordingly, even though the voltage envelope for different voltage signals generated by the circuit boards will have substantially the same phase angle, the PWM signals used to generate these voltage signals do not have substantially the same phase angle, thereby helping to minimize DC link capacitance and electromagnetic noise.
  • a plurality of electric motors could be mounted to a vehicle where at least one of the electric motors has different motor characteristic values to the to the other electric motors, for example different torque efficiency values.
  • the different electric motors which are preferably in-wheel electric motors, are driven to have different a motor characteristic value.
  • two electric motors could be driven to provide a torque value, where the two electric motors operate with a first torque efficiency value, and another pair of electric motors are driven to prove the torque value with the electric motors have a second torque efficiency value.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Control Of Multiple Motors (AREA)
  • Control Of Ac Motors In General (AREA)
  • Brushless Motors (AREA)
  • Control Of Electric Motors In General (AREA)

Abstract

An electric motor arrangement comprising an electric motor having a rotor, a stator, a first coil set and a second coil set, wherein the first coil set is arranged to form a first sub motor with a control device being arranged to control current in the first coil set to generate a first torque on the rotor and the second coil set is arranged to form a second sub motor with the control device being arranged to control current in the second coil set to generate a second torque on the rotor, wherein the first sub motor is arranged to have a first torque efficiency profile and the second sub motor is arranged to have a second torque efficiency profile; and a controller for determining a first torque value generated by the first sub motor and a second torque value generated by the second sub motor in response to a requested torque demand based on a required torque efficiency profile for the electric motor.

Description

ELECTRIC MOTOR
The present invention relates to an electric motor and in particular an in-wheel electric motor.
Electric motor systems typically include an electric motor and a control unit arranged to control the power of the electric motor, which may be configured as either a rotary or linear electric motor. Examples of known types of electric motor include the induction motor, synchronous brushless permanent magnet motor and switched reluctance motor. In the commercial arena three phase electric motors are the most common kind of electric motor available. A three phase electric motor typically includes three coil sets, where each coil set is arranged to generate a magnetic field associated with one of the three phases of an alternating voltage. To increase the number of magnetic poles formed within an electric motor, each coil set will typically have a number of coil sub-sets that are distributed around the periphery of the electric motor, which are driven to produce a rotating magnetic field.
By way of illustration, Fig. 1 shows a typical three phase electric motor 10 having three coils 14, 16, 18. Each coil consists of four coil sub-sets that are connected in series. Accordingly, for a given coil set the magnetic field generated by the respective coil sub-sets will have a common phase .
The three coil sets of a three phase electric motor are typically configured in either a delta or wye configuration, where a delta configuration is illustrated in Fig. 2 and a wye configuration is illustrated in Fig. 3. A control unit for a three phase electric motor having a DC power supply will typically include a three phase bridge inverter that generates a three phase voltage supply for driving the electric motor. Each of the respective voltage phases is applied to a respective coil set of the electric motor .
A three phase bridge inverter includes a number of switching devices, for example power electronic switches such as Insulated Gate Bipolar Transistor (IGBT) switches.
For any given motor configuration an electric motor will typically have motor characteristics that have different values at different speed or torque settings. For example, the torque efficiency of an electric motor at one torque value will typically be different to the torque efficiency of the electric motor at a different torque value, where the set of torque efficiency values of an electric motor are normally illustrated in a torque efficiency profile, which is used to map the efficiency of an electric motor at a range of motor speed/torque ratios.
Accordingly, an electric motor will inevitably have greater efficiency at one speed/torque ratio compared to another speed/torque ratio.
For an electric motor that is only expected to operate within a limited speed/torque range, an electric motor can be designed to have optimum torque efficiency in this range. However, for an electric motor that is expected to operate in a wide range of speed/torque ranges, for example an electric motor designed to drive a vehicle, it will be inevitable that the electric motor will be required at times to operate in a relatively inefficient speed/torque range.
It is desirable to improve this situation. In accordance with an aspect of the present invention there is provided an electric motor according to the accompanying claims . The present invention allows an electric motor to have a number of sub motors that can operate independently of each other, where each of the sub motors has a set of values for a motor characteristic that are different to at least one other sub motor. For example, the motor characteristic could be torque/speed efficiency. For such an example, each sub motor can be operated independently with the torque demand for each sub motor being selected based on the torque/speed efficiency map associated with each sub motor, thereby selectively providing a required overall torque/speed efficiency for the electric motor and consequently allowing an electric motor to operate in an efficient speed torque range for a wide range of torque demands.
Additionally, the current flow in the coil sub-sets of one coil set is independent of the current flow in the coil sub¬ sets of another coil set (i.e. the respective coil sub-sets are not connected in series) . Consequently, the coils of each coil sub-set can have a larger number of turns than for an equivalent motor in which all respective coil sub-sets are connected in series. The increased number of turns in each coil increases the overall inductance of the motor. This means that lower currents can be used in the coils of each coil sub-set, which leads to fewer heat dissipation problems, and which allows smaller switching devices to be used. The use of smaller switching devices in turn allows for faster switching speeds and lower switching losses.
Further, as the coils of a coil sub-set are arranged to form a multi-phase electric motor (i.e. forms a logical sub- motor) the coils of a coil sub-set can be configured either in a delta or wye configuration as best fits the specific electric motor requirements. The respective control devices, otherwise known as drive units, include an inverter having a plurality of switches for applying a pulse width modulated (PWM) voltage to the plurality of respective coil sub-sets, which is used to control current within the coils of the coil sub-set. PWM control of the currents in the motor coils can be enhanced due to the increased number of turns that can be included in the coils. As smaller switching device can be used, significant savings in cost, weight and heat dissipation can be made.
Since smaller components (e.g. switching devices) can be used within the control devices they can be housed within a casing of the motor. For example, the control devices can be located adjacent the coil sub-sets of the respective coil set within the motor thereby simplifying termination of the coil windings. The casing of the motor can include one or more apertures dimensioned such that the control devices can be accessed one at a time, depending on the orientation of the rotor/casing and the control devices.
A common control device can be provided to coordinate the operation of the plurality of control devices, thereby allowing the independent sub-motors of the electric motor to be centrally controlled. Accordingly, the common control device can be operable to selectively disable one or more of the control devices to allow fractional power operation or to adjust the power of one sub-motor to compensate for a fault in another sub-motor.
An electric motor having parallel sub-motors reduces current per coil set compared to an electric motor having serially coupled coil sets. Further by having the control devices for each sub motor located within the electric motor assembly, with associated capacitance also located within the electric motor assembly, reduces the capacitance requirements for the electric motor. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which :
Figure 1 schematically shows an example of three phase motor arrangement ;
Figure 2 illustrates a three phase motor delta coil wiring arrangement;
Figure 3 illustrates a three phase motor wye coil wiring arrangement ; Figure 4 illustrates an exploded view of a motor embodying the present invention;
Figure 5 is an exploded view of the motor of Figure 3 from an alternative angle;
Figure 6 schematically shows an example arrangement of coil sets for an electric motor according to an embodiment of the present invention; Figure 7 illustrates a first torque efficiency map associated with a first subset of sub motors;
Figure 8 illustrates a second torque efficiency map associated with a second subset of sub motors;
Figure 9 schematically illustrates the coils sub-sets of an electric motor according to an embodiment of the present invention that are configured in a wye configuration; Figure 10 schematically illustrates the coils sub-sets of an electric motor according to an embodiment of the present invention that are configured in a delta configuration; Figure 11 schematically shows an example of a control device in accordance with an embodiment of the present invention;
Figure 12 is a circuit diagram of the switching arrangement.
The embodiment of the invention described is an electric motor for use in a wheel of a vehicle. The motor is of the type having a set of coils being part of the stator for attachment to a vehicle, radially surrounded by a rotor carrying a set of magnets for attachment to a wheel. For the avoidance of doubt, the various aspects of the invention are equally applicable to an electric generator having the same arrangement. As such, the definition of electric motor is intended to include electric generator. In addition, some of the aspects of the invention are applicable to an arrangement having the rotor centrally mounted within radially surrounding coils.
The physical arrangement of the embodying assembly is best understood with respect to Figures 4 and 5. The assembly can be described as a motor with built in electronics and bearing, or could also be described as a hub motor or hub drive as it is built to accommodate a separate wheel. Referring first to Figure 4, the assembly comprises a stator 252 comprising a rear portion 230 forming a first part of the housing of the assembly, and a heat sink and drive arrangement 231 comprising multiple coils and electronics to drive the coils as well as a heat sink. The coil drive arrangement 231 is fixed to the rear portion 230 to form the stator 252 which may then be fixed to a vehicle and does not rotate during use. The coils themselves are formed on tooth laminations which together with the drive arrangement 231 and rear portion 230 form the stator 252.
Although not shown, also mounted to the stator are a plurality of capacitor circuit boards for providing capacitance between the electric motor and the voltage supply to reduce voltage line drop.
A rotor 240 comprises a front portion 220 and a cylindrical portion 221 forming a cover, which substantially surrounds the stator 252. The rotor includes a plurality of magnets 242 arranged around the inside of the cylindrical portion 221. The magnets are thus in close proximity to the coils on the assembly 231 so that magnetic fields generated by the coils in the assembly 231 generate a force on the magnets 242 arranged around the inside of the cylindrical portion 221 of the rotor 240 thereby causing the rotor 240 to rotate . The rotor 240 is attached to the stator 252 by a bearing block 223. The bearing block 223 can be a standard bearing block as would be used in a vehicle to which this motor assembly is to be fitted. The bearing block comprises two parts, a first part fixed to the stator and a second part fixed to the rotor. The bearing block is fixed to a central portion 233 of the wall 230 of the stator 252 and also to a central portion 225 of the housing wall 220 of the rotor 240. The rotor 240 is thus rotationally fixed to the vehicle with which it is to be used via the bearing block 223 at the central portion 225 of the rotor 240. This has a significant advantage in that a wheel rim and tyre can then be fixed to the rotor 240 at the central portion 225 using the normal wheel bolts to fix the wheel rim to the central portion of the rotor and consequently firmly onto the rotatable side of the bearing block 223. The wheel bolts may be fitted through the central portion 225 of the rotor through into the bearing block itself. A first advantage of this arrangement is that the whole assembly may be simply retrofitted to an existing vehicle by removing the wheel, bearing block and any other components such as the braking arrangement. The existing bearing block can then fitted inside the assembly and the whole arrangement fitted to the vehicle on the stator side and the normal rim and wheel fitted to the rotor so that the rim and wheel surrounds the whole motor assembly. Accordingly, retrofitting to existing vehicles becomes very simple. A second advantage is that there are no forces for supporting the vehicle on the outside of the rotor 240, particularly on the circumferential wall 221 carrying the magnets on the inside circumference. This is because the forces for carrying the vehicle are transmitted directly from the suspension fixed to one side of the bearing block (via the central portion of the stator wall) to the central portion of the wheel surrounding the rotor fixed to the other side of the bearing block (via the central portion of the rotor wall) . This means that the circumferential wall 221 of the rotor is not subject to any forces that could deform the wall thereby causing misalignment of the magnets. No complicated bearing arrangement is needed to maintain alignment of the circumferential rotor wall. Figure 5 shows an exploded view of the same assembly as Figure 4 from the opposite side showing the stator 252 comprising the rear stator wall 230 and coil and electronics assembly 231. The rotor 240 comprises the outer rotor wall 220 and circumferential wall 221 within which magnets 242 are circumferentially arranged. As previously described, the stator 252 is connected to the rotor 240 via the bearing block 223 at the central portions of the rotor and stator walls . Additionally shown in Figure 4 are control devices 80, otherwise known as motor drive circuits, which, as described below, includes an inverter. Additionally in Figures 4 and 5 a V shaped seal 350 is provided between the circumferential wall 221 of the rotor and the outer edge of the stator housing 230. Further, in Figure 5, the magnetic ring 227 comprising a commutation focusing ring and a plurality of magnets is provided for the purpose of indicating the position of the rotor with respect to the stator to a series of sensors arranged on the control devices 80 of the stator 252.
Figure 6 schematically shows an example of an electric motor 40 in accordance with an embodiment of this invention. In this example, the motor is generally circular. However, it will be appreciated that embodiments of this invention can employ other topologies. For example a linear arrangement of coils for producing linear movement is envisaged.
The motor 40 in this example includes eight coil sets 60 with each coil set 60 having three coil sub-sets 61, 62, 63 that are coupled to a respective control device 64, where each control device 64 and respective coil sub-sets form a three phase logical or sub electric motor that can be controlled independently of the other sub motors. The control devices 64 drive their respective sub motor with a three phase voltage supply, thereby allowing the respective coil sub-sets to generate a rotating magnetic field. Although the present embodiment describes each coil set 60 as having three coil sub-sets 61, 62, 63, the present invention is not limited by this and it would be appreciated that each coil set 60 could have two or more coil sub-sets. Equally, although the present embodiment describes an electric motor having eight coil sets 60 (i.e. eight sub motors) the motor could have two or more coil sets with associated control devices (i.e. two or more sub motors) .
The motor 40 can include a rotor (not shown in Figure 6) positioned in the centre of the circle defined by the positioning of the various coils of the motor, thereby to allow rotation of the rotor within the rotating magnetic field produced by the coils. Preferably, though, the rotor is arranged around the coils as previously disclosed in Figures 4 and 5. The rotor may typically comprise one or more permanent magnets arranged to rotate such that their poles sweep across the ends of the coils of the motor 40. Appropriate switching of currents in the coils of the coil sub-sets 61, 62, 63 allows synchronized attraction and repulsion of the poles of the permanent magnet of the rotor to produce the rotating action of the motor 40. It will be appreciated that Figure 6 is highly schematic and, in practice, the coil sub-sets will be arranged at the outer periphery of the stator with the rotor magnets surrounding the coils.
As stated above, each control device includes a three phase bridge inverter which, as is well known to a person skilled in the art, contains six switches. The three phase bridge inverter is coupled to the three subset coils of a coil set
60 to form a three phase electric motor configuration.
Accordingly, as stated above, the motor includes eight three phase sub-motors, where each three phase sub-motor includes a control device 64 coupled to the three sub-set coils of a coil set 60.
Each three phase bridge inverter is arranged to provide PWM voltage control across the respective coil sub-sets 61, 62, 63 to provide a required torque for the respective sub- motors .
For a given coil set the three phase bridge switches of a control device 64 are arranged to apply a single voltage phase across each of the coil sub-sets 61, 62, 63.
Torque, otherwise known as moment of force, is a measure of the turning force on the rotor and is a product of the force on the rotor and rotor radius .
Within an electric motor, torque is typically proportional to current flow in the electric motors coil windings. Efficiency of a motor is defined by the ratio of output mechanical power to input electrical power, where a torque/speed efficiency map defines the efficiency of an electric motor over a range of speed and torque values. Torque/speed efficiency of an electric motor can vary as a result of many features within the motor. For example, the number of coil windings formed on tooth laminations, the diameter of the coils used to form the coil windings on the tooth laminations, the shape of the stator teeth and/or the air gap between the end of the tooth laminations and the rotor magnets, and the voltage applied across the coils. For the purposes of the present embodiment, to allow an optimum torque/speed efficiency to be produced for the electric motor at least two of the sub motors are arranged to have a torque/speed efficiency map that have different sets of values. However, the set of torque/speed efficiency values can be varied between any number of the different sub motors .
As stated above, the present invention is not limited to different sets of torque/speed efficiency values, other motor characteristics can be varied between different sub motors, either in addition to torque/speed efficiency values or as an alternative.
To allow the torque/speed efficiency map to be varied between different sub motors, any suitable sub motor design feature can be changed. For example, any one or more of the following features can be varied between different sub motors: the number of coil windings formed on tooth laminations, the diameter of the coils used to form the coil windings on the tooth laminations, the shape of the stator teeth and/or the air gap between the end of the tooth laminations and the rotor magnets, and the voltage applied across the coils. Additionally, or alternatively, the respective sub motors can be driven to generate a predetermined torque/speed efficiency map.
The design criteria for determining the torque/speed efficiency map values for any one of the sub motors will typically be determined based on the intended use of the electric motor. For example, in the present embodiment, in which the electric motor has eight sub motors, the electric motor may be designed to have four sub motors with a torque/speed efficiency map that is substantially the same as a first torque/speed efficiency map, while the other four sub motors are arranged to have a torque/speed efficiency map that is substantially the same as a second torque/speed efficiency map. However, the electric motor can be designed to have any arrangement of torque/speed efficiency map/sub motor configuration, for example three of the sub motors could have substantially the same torque/speed efficiency map with the other five sub motors having a different torque/speed efficiency map. Alternatively, all of the sub motors could be arranged to have different torque/speed efficiency maps. It should be noted that the torque/speed efficiency map for a first set of sub motors can be selected to be different to the torque/speed efficiency map for a second set of sub motors (i.e. a first set of sub motors can be regarded as being equivalent to a first sub motor with a predetermined torque/speed efficiency map with a second set of sub motors being regarded as being equivalent to a second sub motor with a predetermined torque/speed efficiency map) . Accordingly, any combination of sub motor/torque/speed efficiency map configuration could be adopted based on the design needs of the electric motor.
Although the present embodiment is based on driving an electric motor having a plurality of sub motors while maximizing torque/speed efficiency, the principle can be applied to regeneration of the electric motor (i.e. treating the electric motor as a generator) , while minimizing electric motor losses.
By way of illustration, an example of how the torque efficiency map for an electric motor having sub motors is optimized to provide improved torque/speed efficiency for a variety of driving conditions will now be described. The following illustration is based on a vehicle having four in wheel electric motors, with each in wheel electric motor having eight sub motors,
For a vehicle primarily intended to be driven in either an urban environment, which typically involves low speeds and high torque, or a highway environment, which typically requires high speed and low torques, four of the eight sub motors for each in wheel electric motor are arranged to have substantially the same torque/speed efficiency map, which when operated together has a torque/speed efficiency map corresponding to the torque/speed efficiency values illustrated in Figure 7. The second set of the eight sub motors are arranged to have substantially the same torque/speed efficiency map, which when operated together has a torque/speed efficiency map corresponding to the torque/speed efficiency values illustrated in Figure 8. Each sub motor has a maximum torque in the region of 200Nm.
The first torque/speed efficiency map, as shown in Figure 7, is configured to have higher torque/speed efficiency values at lower speeds, as typically encountered when driving in an urban environment. The second torque/speed efficiency map, as shown in Figure 8, is configured to have higher torque/speed efficiency values at higher speeds, as typically encountered when driving on the highway.
To allow an optimum torque/speed efficiency to be determined for a given torque/speed demand a table is stored in memory, preferably within the in wheel control device, that defines the amount of torque contribution provided by each set of sub motors, where total torque Ttotai is a sum of torque provided by the first set of sub motors TA and the second set of sub motors TB. Preferably the table lists the percentage contribution of the first set of sub motors and second set of sub motors over the range of available torque values and motor speeds, which for the present embodiment would correspond to a range of 0 to 1600Nm torque and 0 to 1200rpm. The table can be created using any suitable means, for example by populating the table with percentage contributions to provide optimum torque/speed efficiency at specified torque/speed points.
For example, to provide optimum torque/speed efficiency for a torque demand of 450Nm and motor speed of 300 rpm the contribution provided by the first set of sub motors would be 100%. The torque contribution provided by the second set of sub motors would be 0%. The torque contribution is determined by the electric current generated in the coil windings associated with the respective sub motors. For a torque demand of 250Nm and motor speed of 700rpm the torque contribution provided by the second set of sub motors would be 100%. The torque contribution provided by the first set of sub motors would be 0%. However, for most situations both sets of sub motors will provide a torque contribution, particularly if the total torque requirement exceeds that available per set of sub motors. For example, for a torque demand of 700Nm at 700rpm a possible scenario would be for 500Nm to be provided by the first set of sub motors, operating with between 88% and 90% torque/speed efficiency, and 200Nm would be provided by the second set of sub motors operating at around 90% torque/speed efficiency. Accordingly, for a required torque value the current flow in the coil windings of the respective sub motors is selected to provide a predetermined torque efficiency for the electric motor. In other words, the required torque value for the electric motor may be fixed but the current selected to flow through the coil windings of the respective sub motors is varied/selected to provide a predetermined torque efficiency for the electric motor based on a sum of the torque efficiencies of the respective sub motors and their contribution to the overall torque generated by the electric motor .
Although the present embodiment utilizes a table to define the ratio of torque generated by the respective sub motors at a required speed, the ratio of torque generated by the respective sub motors at a required speed can also be determined by other means, for example using an algorithm. Alternatively, some form of control loop could be implemented in which the contribution of torque provided by different sub motors is varied using a feedback loop to provide an optimized torque efficiency for an electric motor for a given overall torque value.
Additionally, the means for determining the ratio of torque generated by the respective sub motors can also be configured to accommodate changes in temperature of the respective sub motors. For example, to avoid overheating of a sub motor, once the temperature of a sub motor has exceeded a threshold value a different ratio of torque generation may be adopted to avoid overheating of a sub motor . Figure 9 illustrates the electric motor shown in Figure 6, where each control device bridge inverter is coupled to their respective coil sub-sets to form a wye configuration.
Figure 10 illustrates the electric motor shown in Figure 6, where each control device bridge inverter is coupled to their respective coil sub-sets to form a delta configuration .
To provide a different torque efficiency map between sub motors, one set of sub motors can be coupled in a wye configuration while the other set of sub motors can be coupled in a delta configuration. Figure 11 shows an example of a control device 80 in accordance with an embodiment of this invention.
The control device 80 includes a first circuit board 83 and a second circuit board 82. Preferably the second board 82 is arranged to overlay the first circuit board 83, as illustrated in Figure 11.
The first circuit board 83 includes a plurality of switches that are arranged to apply an alternating voltage across the respective coil sub-sets. The switches can include semiconductor devices such as MOSFETs or IGBTs. In the present embodiment the switches comprise IGBT switches. As described above, the plurality of switches are configured to form an n-phase bridge circuit. Accordingly, as is well known to a person skilled in the art, the number of switches will depend upon the number of voltage phases to be applied to the respective sub motors. In the present embodiment, in which the control devices and coil sub-sets are configured to form a three phase motor, the first circuit board 83 of the respective control devices include six switches. Although the current design shows each sub motor having a three phase construction, the sub motors can be constructed to have two or more phases.
The wires (e.g. copper wires) of the coil sub-sets can be connected directly to the switching devices as appropriate. The second circuit board 82 includes a number of electrical components for controlling the operation of the switches mounted on the first circuit board 83. Examples of electrical components mounted on the second circuit board 82 include control logic for controlling the operation of the switches for providing PWM voltage control and interface components, such as a CAN interface chip, for allowing the control device 80 to communicate with devices external to the control device 80, such as other control devices 80 or a master controller. Typically the second control board 82 will communicate over the interface to receive torque demand requests and to transmit status information. As mentioned above, the second circuit board 82 is arranged to be mounted on top of the first circuit board 83, where the first circuit board 83 and the second circuit board include means for being mounted within the motor 40, for example, adjacent to the coil sub-set which they control, directly to a cooling plate. In the illustrated example, these means include apertures 84 through which screws or suchlike can pass. In this example, the first circuit board 83 and the second circuit board 82 are substantially wedge- shaped. This shape allows multiple control devices 80 to be located adjacent each other within the motor, forming a fanlike arrangement. By separating the control logic from the switches this has the advantage of thermally isolating the control logic from the switches while also minimizing the impact of any electrical noise generated by the switches.
Also mounted on each of the circuit boards is a sensor that can be used for determining the position of the rotor 240, for example a hall sensor that is arranged to generate an electrical signal dependent upon the relative position of the focusing ring and magnets 227 that is mounted on the rotor 240. To determine the direction that the rotor is turning in the circuit boards preferably have two sensors that are offset by a predetermined angle so that the changes in signal from each of the sensors can be analyzed to determine both the relative position of the rotor 240 and the direction of rotation of the rotor. To allow each control device, and hence each sub motor, to operate independently of each other each circuit board has their own set of position sensors. However, a single set of position sensors could be used.
Figure 12 illustrates six switches of the first circuit board arranged in an 3 phase bridge configuration that are coupled to the coil sub-sets of a coil set that are placed in a wye configuration. The six semiconductor switches are connected to a voltage supply, for example 300 volts, and to ground. Pairs of the respective coil sub-sets are connected between two legs of the bridge circuit. Simplistically, to operate the motor and supply a voltage in one direction, the switches are operated in pairs, one in the top half of the bridge and one from a different leg in the bottom half of the bridge. Each switch carries the output current for one third of the time.
To change the direction of rotation of the motor, the timing and polarity of the current flow in the coil is changed to cause the resulting forces in the opposite direction. As described above, the technique of pulse width modulating is used to pulse width modulate the signal applied to the gate of the semiconductor switches to control the voltage applied to the coils, where the PWM voltage is determined based uon a received torque demand request. The PWM voltage in turn determines the coil current and hence the produced torque.
As each sub motor of an in-wheel electric motor operates independently of the other sub motors (i.e. the sub motors are not serially connected) , to improve torque balance between the respective sub motors a common control device can be located within the in-wheel electric motor for monitoring and adjusting the operation of the respective sub motors to balance the operation of the respective sub motors .
Alternatively, the balancing and synchronization of the respective sub motors can be performed by one or more of the sub motor control devices 80, where the in-wheel electric motor control devices 80 communicate between each other via the communication bus.
In a vehicle incorporating a plurality of wheels each having an in-wheel electric motor 40, each motor incorporates all the intelligence needed to manage its actions. Each motor understands its position on the vehicle and controls its actions accordingly. Preferably, each motor is further provided with information regarding the other motors such as the speed, torque and status and are based on each motor' s knowledge of its position on the vehicle and the state and status of the other motors it can determine the optimum level of torque that it should apply for a given demanded torque. Even without this other information, though, the motor can continue to respond to a demanded torque.
Other control signals such as power up/power down control signals can also be sent/received to/from a master controller that is arranged to control the overall operation of the vehicle to which the respective in-wheel electric motors are mounted. The control signals are communicated to the respective control devices 80 for an in-wheel electric motor either directly or indirectly via a common control device. As described above, the control signals will typically be communicated via the communication bus, for example a CAN bus. However, as would be appreciated by a person skilled in the art, the signals can be communicated by any suitable means. The control signals can also include signals for adj usting/defining the voltage pulses applied by the control device 80 to the coils of its associated coil sub-set for powering the motor and thereby adjust the torque demand for the in-wheel electric motor.
As stated above, each electrical signal generated to drive the different coil sub-sets, within a given coil set, have a different phase angle. Each electrical signal generated by different circuit boards has substantially the same phase angle as corresponding electrical signals generated by other circuit boards. For example, for a three phase motor, where each sub motor includes a coil set having three coil sub¬ sets, each sub motor will generate an electrical signal having a first phase angle that is substantially the same for each sub motor. Similarly, each sub motor in a three phase motor will also generate electrical signals having a second and third phase angle, where the second and third phase angles are substantially the same between the sub motors .
The phase angle and voltage envelope for each of the different electrical signals are generated by the respective circuit boards using PWM voltage control, where the voltage envelope and phase angle of the electrical signals is determined by the modulating voltage pulses.
However, to minimize DC link capacitance and electromagnetic noise, the PWM voltage signals generated by each sub motor for electrical signals having a voltage envelope with substantially the same phase angle are offset with respect to each other. That is to say, even though the voltage envelope for different signals generated by different sub motors is substantially the same, the PWM signal used to generate these voltage signals are offset with respect to each other.
To achieve the PWM offset between different sub motors, PWM counters for each of the different sub motors are synchronized and an offset synchronous signal is generated for the counters on the different circuit boards, where the offset synchronous signal is different for each circuit board (i.e. for each sub motor) . This has the effect of phase shifting the PWM voltage for each corresponding electric phase signal provided by each circuit board. Accordingly, even though the voltage envelope for different voltage signals generated by the circuit boards will have substantially the same phase angle, the PWM signals used to generate these voltage signals do not have substantially the same phase angle, thereby helping to minimize DC link capacitance and electromagnetic noise.
It will be apparent to those skilled in the art that the disclosed subject matter may be modified in numerous ways and may assume embodiments other than the preferred forms specifically set out as described above, for example a plurality of electric motors could be mounted to a vehicle where at least one of the electric motors has different motor characteristic values to the to the other electric motors, for example different torque efficiency values. Accordingly, similarly to the embodiment described above, where different sub-motors are driven to have different a motor characteristic value, the different electric motors, which are preferably in-wheel electric motors, are driven to have different a motor characteristic value. For example, two electric motors could be driven to provide a torque value, where the two electric motors operate with a first torque efficiency value, and another pair of electric motors are driven to prove the torque value with the electric motors have a second torque efficiency value.

Claims

1. An electric motor arrangement comprising an electric motor having a rotor, a stator, a first coil set and a second coil set, wherein the first coil set is arranged to form a first sub motor and the second coil set is arranged to form a second sub motor, wherein the first sub motor and the second sub motor have a motor characteristic that has a first set of values for the first sub motor and a second set of values for the second sub motor; and a controller for determining a first current value to be provided to the first sub motor and a second current value to be provided to the second sub motor to provide the electric motor with the motor characteristic having a predetermined or optimised value.
2. An electric motor according to claim 1, wherein the motor characteristic is torque/speed efficiency and the first set of values forms a first torque/speed efficiency map and the second set of values forms a second torque/speed efficiency map.
3. An electric motor according to any one of the preceding claims, wherein the controller is arranged to determine the first current value and the second current value in response to a received torque or speed demand.
4. An electric motor according to claim 3, wherein the controller is arranged to determine the first current value and the second current value in response to a received torque or speed demand using a look-up table, or an algorithm or a control loop.
5. An electric motor arrangement according to claim 3 when dependent upon claim 2, wherein a difference in torque/speed efficiency map between the first torque/speed efficiency map and the second torque/speed efficiency map is determined by at least one of the following: i) the number of coil winding turns that form the first coil set and the second coil set; ii) the diameter of coil windings that form the first coil set and the second coil set; iii) the type of wiring connection for the first coil set and the second coil set; or iv) the shape and/or dimensions of the stator teeth that form part of the first sub motor and the second sub motor.
6. An electric motor according to any one of the preceding claims, wherein each coil set includes a plurality of coil sub-sets.
7. An electric motor according to any one of the preceding claims, further comprising a control device arranged to control current in the first coil set to generate a first torque on the rotor and to control current in the second coil set to generate a second torque on the rotor.
8. An electric motor according to claim 6, wherein the control device is arranged to drive each of the coil sub- sets with a different voltage phase angle.
9. An electric motor according to claim 8, wherein the control device is arranged to control the voltage to each coil sub-set using pulse width modulation.
10. An electric motor arrangement according to claims 7 or 8, wherein the control device is arranged as a first control device for the first sub motor and a second control device for the second sub motor.
11. An electric motor arrangement according to claim 10, wherein the first control device and the second control device are mounted adjacent to the stator.
12. An electric motor according to claims 10 or 11, wherein the first control device and second control device include six switches arranged as a three phase bridge for controlling the voltage provided to the respective coil sub¬ sets .
13. An electric motor according to any one of claims 10 to 12, wherein the first control device and the second control device have a plurality of switches mounted on a first circuit board and a controller mounted on a second circuit board that is arranged to control the operation of the plurality of switches on the first circuit board to provide a voltage to the coil sub-sets.
14. An electric motor according to any one of claims 10 to 13, further comprising a sensor arranged to detect the position of a rotor of the electric motor to generate a position signal, wherein the first control device and second control device are arranged to control voltage to the respective coil sub-sets using the position signal.
15. An electric motor according to claim 14, wherein the rotor includes a plurality of magnets, wherein the sensor is arranged to determine the position of the rotor by detecting the position of the magnets.
16. An electric motor according to any one of claims 10 to 15, wherein each control device includes a sensor arranged to detect the position of a rotor of the electric motor to generate a position signal, wherein each control device is arranged to control voltage to the respective coil sub-set using the respective position signal.
17. An electric motor according to any one of claims 10 to 16, wherein each control device includes a plurality of sensors arranged to detect the position of a rotor of the electric motor to generate a position signal and direction of rotation of the rotor signal, wherein each control device is arranged to control voltage to the respective coil sub¬ set using the respective position and direction signal.
18. An electric motor according to any one of claims 10 to 17, wherein the first control device and the second control device are arranged to receive a torque demand request and arranged to control current in the coil sub-sets based on the torque demand request.
19. An electric motor according to any one of the preceding claims, wherein each coil sub-set includes a plurality of adjacent coils.
20. An electric motor according to any one of claims 10 to 19, wherein the first control device and the second control device are mounted to the stator.
21. An electric motor according to claim 20, wherein the stator further comprises a heat sink with the first control device and the second control device being mounted to the heat sink.
22. An electric motor according to any one of claims 10 or
21, wherein the first control device and the second control device are located adjacent their respective coil sub-sets within the electric motor.
23. An electric motor according to any one of claims 10 to
22, wherein the first control device and second control device are coupled via a communication interface to allow the first control device and the second control device to communicate.
24. An electric motor according to any one of claims 10 to
23, wherein the first control device is mounted on the stator adjacent to the first coil set and the second control device is mounted on the stator adjacent to the second coil set .
25. An electric motor according to claim 24, wherein the coil sets are mounted circumferentially around the axis of the stator at different angles around the axis with the respective control device being mounted to the stator at substantially the same angle as the respective coil set.
26. An electric motor according to any one of claims 10 to 25, wherein the control devices are arranged to that the magnetic field in each coil sub set is generated using pulse width modulation voltage control.
27. An electric motor according to claim 26, wherein the control devices are arranged so that the magnetic phase angle of the magnetic field generated in the respective coil sub-sets of the first coil set is substantially the same as the magnetic phase angle of the magnetic field generated in the respective coil sub-sets of the second coil set.
28. An electric motor according to claim 27, wherein the control devices are arranged so that the pulse width modulation voltage signals used to generate the magnetic field in the first coil set are offset with respect to the pulse width modulation voltage control signal used to generate the magnetic field in the second coil set.
PCT/IB2011/052664 2010-07-19 2011-06-17 Electric motor with varying torque efficiency profile WO2012010993A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1012092.1 2010-07-19
GB1012092.1A GB2472297B (en) 2010-07-19 2010-07-19 Electric motor

Publications (2)

Publication Number Publication Date
WO2012010993A2 true WO2012010993A2 (en) 2012-01-26
WO2012010993A3 WO2012010993A3 (en) 2013-05-10

Family

ID=42735140

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2011/052664 WO2012010993A2 (en) 2010-07-19 2011-06-17 Electric motor with varying torque efficiency profile

Country Status (3)

Country Link
CN (1) CN102263469B (en)
GB (1) GB2472297B (en)
WO (1) WO2012010993A2 (en)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014037920A3 (en) * 2012-09-10 2015-04-16 Protean Electric Limited An electric motor or generator
WO2014080361A3 (en) * 2012-11-23 2015-07-30 Protean Electric Limited A control system for an electric motor
WO2021101639A1 (en) * 2019-11-20 2021-05-27 Tula Etechnology Inc. Pulsed electric machine control using tables
US11133767B2 (en) 2018-03-19 2021-09-28 Tula eTechnology, Inc. Pulsed electric machine control using tables
US11557996B1 (en) 2021-07-08 2023-01-17 Tula eTechnology, Inc. Methods of reducing vibrations for electric motors
US11626827B2 (en) 2018-03-19 2023-04-11 Tula eTechnology, Inc. Pulsed electric machine control
US11623529B2 (en) 2018-03-19 2023-04-11 Tula eTechnology, Inc. Pulse modulated control with field weakening for improved motor efficiency
US11628730B2 (en) 2021-01-26 2023-04-18 Tula eTechnology, Inc. Pulsed electric machine control
US11637466B1 (en) 2021-10-18 2023-04-25 Tula Etechnology Inc. Mechanical and electromechanical arrangements for field-weakening of an electric machine that utilizes permanent magnets
US11637513B2 (en) 2021-03-15 2023-04-25 Tula eTechnology, Inc. Methods of optimizing waveforms for electric motors
US11673476B2 (en) 2021-08-12 2023-06-13 Tula eTechnology, Inc. Method of optimizing system efficiency for battery powered electric motors
US11695361B2 (en) 2021-06-14 2023-07-04 Tula eTechnology, Inc. Electric machines with efficient torque transitions
US11863096B2 (en) 2018-03-19 2024-01-02 Tula eTechnology, Inc. Boosted converter for pulsed electric machine control
US11888424B1 (en) 2022-07-18 2024-01-30 Tula eTechnology, Inc. Methods for improving rate of rise of torque in electric machines with stator current biasing
US11916498B2 (en) 2021-09-08 2024-02-27 Tule eTechnology Inc. Electric machine torque adjustment based on waveform integer multiples
US11973447B2 (en) 2021-06-28 2024-04-30 Tula eTechnology, Inc. Selective phase control of an electric machine
US12003202B2 (en) 2023-03-08 2024-06-04 Tula eTechnology, Inc. Pulsed electric machine control

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012120682A1 (en) * 2011-03-10 2012-09-13 パイオニア株式会社 Efficiency map generation device, efficiency map generation method, and program
GB2483177B (en) 2011-10-19 2013-10-02 Protean Electric Ltd An electric motor or generator
DE102012207534A1 (en) * 2012-05-07 2013-11-07 Siemens Aktiengesellschaft Selection unit for selecting the configuration of an electric motor, transport machine and associated method
GB2494785B (en) * 2012-09-25 2013-11-27 Protean Electric Ltd A control system for identiying an electrical device in a vehicle
DE102014203553A1 (en) 2014-02-27 2015-08-27 Robert Bosch Gmbh Electric drive system
CN106976391A (en) * 2017-02-22 2017-07-25 安徽易威斯新能源科技股份有限公司 A kind of wheel hub motor for allowing hand over torsion and its torsion switching method
GB2554589B (en) 2017-11-10 2019-08-21 Protean Electric Ltd A control device
US10675984B2 (en) 2018-08-03 2020-06-09 American Axle & Manufacturing, Inc. Drive system and method for vehicle employing multiple electric motors
EP3618268A1 (en) * 2018-08-29 2020-03-04 ABB Schweiz AG Method of controlling an electrical machine
JP7299477B2 (en) * 2019-03-27 2023-06-28 ダイキン工業株式会社 electric motor system
US11446960B2 (en) 2019-08-27 2022-09-20 Toyota Motor Engineering & Manufacturing North America, Inc. Modular axle and motive wheel system for a vehicle
US11390163B2 (en) 2019-08-27 2022-07-19 Toyota Motor Engineering & Manufacturing North America, Inc. Variable wheel drive electric vehicle comprising selectively attachable and detachable electric hub motors and method of using the same
DE102020204326A1 (en) * 2020-04-02 2021-10-07 Adaptive Balancing Power GmbH Double motor unit for a flywheel mass storage device with non-linear overall performance characteristic
DE102020130512A1 (en) * 2020-11-18 2022-05-19 Bode - Die Tür Gmbh Method and system for condition-based maintenance of an access device

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0622264B1 (en) * 1993-04-28 1998-11-11 Hitachi, Ltd. Electric vehicle drive system and drive method
US6046554A (en) * 1998-02-13 2000-04-04 General Electric Company Method and apparatus for calibrating a permanent-magnet motor using back EMF measurement
JP2001327132A (en) * 2000-05-18 2001-11-22 Mitsubishi Electric Corp Pole change induction motor
US6847147B2 (en) * 2003-01-29 2005-01-25 Wavecrest Laboratories, Llc Dynamoelectric machine having windings that differ in wire gauge and number of winding turns
GB2456349A (en) * 2008-01-14 2009-07-15 Pml Flightlink Ltd Hub motor with individually controlled stator coils provides safe braking
GB2462940B8 (en) * 2009-09-03 2012-03-28 Protean Holdings Corp Electric motor and electric generator.
GB2462948B (en) * 2009-10-15 2011-08-31 Protean Holdings Corp Method and system for measuring a characteristic of an electric motor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014037920A3 (en) * 2012-09-10 2015-04-16 Protean Electric Limited An electric motor or generator
KR20150077405A (en) * 2012-09-10 2015-07-07 프로틴 일렉트릭 리미티드 An electric motor or generator
JP2015528686A (en) * 2012-09-10 2015-09-28 プロティアン エレクトリック リミテッド Electric motor or generator
US9985490B2 (en) 2012-09-10 2018-05-29 Protean Electric Limited Electric motor or generator
KR102147313B1 (en) 2012-09-10 2020-08-24 프로틴 일렉트릭 리미티드 Electric motor
WO2014080361A3 (en) * 2012-11-23 2015-07-30 Protean Electric Limited A control system for an electric motor
KR20150088276A (en) * 2012-11-23 2015-07-31 프로틴 일렉트릭 리미티드 A control system for an electric motor
KR101719441B1 (en) 2012-11-23 2017-03-23 프로틴 일렉트릭 리미티드 A control system for an electric motor
US11626827B2 (en) 2018-03-19 2023-04-11 Tula eTechnology, Inc. Pulsed electric machine control
US11863096B2 (en) 2018-03-19 2024-01-02 Tula eTechnology, Inc. Boosted converter for pulsed electric machine control
US11623529B2 (en) 2018-03-19 2023-04-11 Tula eTechnology, Inc. Pulse modulated control with field weakening for improved motor efficiency
US11133767B2 (en) 2018-03-19 2021-09-28 Tula eTechnology, Inc. Pulsed electric machine control using tables
US11427177B2 (en) 2019-11-20 2022-08-30 Tula eTechnology, Inc. Pulsed electric machine control using tables
WO2021101639A1 (en) * 2019-11-20 2021-05-27 Tula Etechnology Inc. Pulsed electric machine control using tables
US11628730B2 (en) 2021-01-26 2023-04-18 Tula eTechnology, Inc. Pulsed electric machine control
US11637513B2 (en) 2021-03-15 2023-04-25 Tula eTechnology, Inc. Methods of optimizing waveforms for electric motors
US11695361B2 (en) 2021-06-14 2023-07-04 Tula eTechnology, Inc. Electric machines with efficient torque transitions
US11973447B2 (en) 2021-06-28 2024-04-30 Tula eTechnology, Inc. Selective phase control of an electric machine
US11557996B1 (en) 2021-07-08 2023-01-17 Tula eTechnology, Inc. Methods of reducing vibrations for electric motors
US11673476B2 (en) 2021-08-12 2023-06-13 Tula eTechnology, Inc. Method of optimizing system efficiency for battery powered electric motors
US11916498B2 (en) 2021-09-08 2024-02-27 Tule eTechnology Inc. Electric machine torque adjustment based on waveform integer multiples
US11637466B1 (en) 2021-10-18 2023-04-25 Tula Etechnology Inc. Mechanical and electromechanical arrangements for field-weakening of an electric machine that utilizes permanent magnets
US11888424B1 (en) 2022-07-18 2024-01-30 Tula eTechnology, Inc. Methods for improving rate of rise of torque in electric machines with stator current biasing
US12003202B2 (en) 2023-03-08 2024-06-04 Tula eTechnology, Inc. Pulsed electric machine control

Also Published As

Publication number Publication date
GB2472297A (en) 2011-02-02
CN102263469B (en) 2015-12-16
GB201012092D0 (en) 2010-09-01
GB2472297B (en) 2014-04-23
CN102263469A (en) 2011-11-30
WO2012010993A3 (en) 2013-05-10

Similar Documents

Publication Publication Date Title
WO2012010993A2 (en) Electric motor with varying torque efficiency profile
US8749192B2 (en) Electric motor and electric generator
US20140340013A1 (en) Electric motor and electric generator
US9065304B2 (en) Electric motors
US9509246B2 (en) Control system for an electric motor
KR101949250B1 (en) Inverter for an electric motor or generator
KR102306850B1 (en) A control system for an electric motor
WO2015036921A2 (en) Electric motor or generator
GB2459061A (en) Electric wheel motor
GB2456351A (en) Hub motor with individually controlled stator coils provides safe braking
GB2518028A (en) An electric motor or generator
GB2456349A (en) Hub motor with individually controlled stator coils provides safe braking

Legal Events

Date Code Title Description
NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11743352

Country of ref document: EP

Kind code of ref document: A2