EP1805888A2 - Machine ca a ordre de phase eleve a enroulement a pas court - Google Patents

Machine ca a ordre de phase eleve a enroulement a pas court

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Publication number
EP1805888A2
EP1805888A2 EP05762757A EP05762757A EP1805888A2 EP 1805888 A2 EP1805888 A2 EP 1805888A2 EP 05762757 A EP05762757 A EP 05762757A EP 05762757 A EP05762757 A EP 05762757A EP 1805888 A2 EP1805888 A2 EP 1805888A2
Authority
EP
European Patent Office
Prior art keywords
machine
winding
windings
inverter
phase
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP05762757A
Other languages
German (de)
English (en)
Inventor
Jonathan Sidney Edelson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Borealis Technical Ltd
Original Assignee
Borealis Technical Ltd
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Filing date
Publication date
Application filed by Borealis Technical Ltd filed Critical Borealis Technical Ltd
Publication of EP1805888A2 publication Critical patent/EP1805888A2/fr
Withdrawn legal-status Critical Current

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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
    • H02P25/18—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 with arrangements for switching the windings, e.g. with mechanical switches or relays
    • H02P25/188—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 with arrangements for switching the windings, e.g. with mechanical switches or relays wherein the motor windings are switched from series to parallel or vice versa to control speed or torque
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
    • H02K3/28—Layout of windings or of connections between windings
    • 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
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K17/00—Asynchronous induction motors; Asynchronous induction generators
    • H02K17/02—Asynchronous induction motors
    • H02K17/12—Asynchronous induction motors for multi-phase current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
    • H02K21/14—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures
    • 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
    • H02K29/03—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems

Definitions

  • the present invention relates to alternating current rotating machines, particularly motors and generators, and their inverter drives.
  • Alternating current induction motors have been developed as suitable power driving sources.
  • Polyphase motors including three phase motors, are widely applied in industrial and similar heavy duty applications.
  • a rotor is rotatably mounted within an annular stator.
  • the stator is wound with N distinct phase windings, connected to an N phase alternating current power supply, where N is an integer greater than two.
  • the rotor is normally provided with a short circuited winding which responds to the stator field to create an induced field.
  • An N phase power supply has phase voltages and currents which are offset from each other by 360/N electrical degrees.
  • the N phase winding thereby develops a magnetic field which moves circumferentially about the stator and rotor.
  • the induced field tends to align with and follow the rotating field to create a rotating force and motion of the rotor as a result of the electromagnetic coupling between the fields of the stator and the rotor.
  • An alternating current motor is commonly driven by an inverter.
  • An inverter is a device capable of supplying alternating current of variable voltage and variable frequency to the alternating current motor, allowing for control of machine synchronous speed and thus of machine speed.
  • the inverter may also be used with alternating current generators, and can cause an alternating current motor to act as a generator for braking applications.
  • An alternating current motor may be an induction motor, a synchronous motor with either a wound rotor or permanent magnet rotor, or a brushless DC motor.
  • the cost of the inverter is considerably greater than the cost of the motor being supplied. It is thus necessary to minimize the size of the inverter power electronics in order to control system cost.
  • the alternating current machine itself may have substantial overload capability, and may carry currents of the order of five to ten times full rated current for periods measured in minutes, the overload capability of the inverter electronics is severely limited. Exceeding the voltage or current ratings of the inverter electronics will swiftly cause device failure. Commonly, inverter electronics is specified such that it can tolerate 150% of nominal full load current for 1 minute, and for any given motor, and inverter will be selected which has the same nominal current capability as that of the motor.
  • Voltage is set internally by the inverter system or by the rectified supply voltage. Voltage overload is normally not specified, and will cause near instantaneous destruction of semiconductor elements.
  • the voltage ratings of the semiconductors instead set the maximum output voltage of the inverter system, and an inverter will be selected which has a maximum output voltage that matches the operating voltage of the motor at full speed.
  • a plurality of mutually exclusive speed ranges between startup and a maximum speed at which a motor can be expected to operate are identified and a different number of the motor stator winding coils that are to be energized are designated for each speed range.
  • the number of energized coils is changed dynamically when the speed crosses a threshold between adjacent speed ranges. Even direct current machines (not covered by the present invention) require increased voltage as speed is increased, if magnetic field strength is maintained as a constant.
  • the required voltage is expressed in terms of Volts/Hertz.
  • the change in series turns may be considered a change in alternating current machine impedance, or current versus voltage relation.
  • an alternating current machine will have a fixed relationship between synchronous speed and impedance, characterized by the Volts/Hertz ratio.
  • a machine wound with a higher Volts/Hertz ratio will have a lower maximum speed, but higher peak low speed torque.
  • N number of different driven electrical phases in a machine
  • Vw Voltage across a winding
  • Vout output to neutral voltage of the inverter
  • winding' herein refers to the group of all of the windings and/or coils and/or conductors of a single phase, unless otherwise specified.
  • the winding that constitutes each phase consists of a 'supply half and a 'back half .
  • the 'supply half is driven by the power supply, and has a phase angle dependent on the power supply phase or phases to which it is connected.
  • the phase angle of the back half of each phase is equal to the phase angle of the supply half, offset by 180 ED.
  • the windings are wound of copper or other low resistance wire or other conductors.
  • Vw 2*sin( (B*H* ⁇ ) /4) *Vout (ii)
  • a mesh connection is disclosed in my previous abovementioned patents and applications.
  • Each of N windings is connected between two of N inverter outputs.
  • a first terminal of each winding phase is connected in phase angle order to one of the N inverter outputs.
  • a phase angle difference is produced by connecting the second terminal of each winding to a second inverter phase.
  • ⁇ represents the phase angle difference between the inverter output phases across the two terminals of each winding. All of the windings in a machine have the same value of ⁇ .
  • a low ⁇ is produced by connecting the first terminal of a winding to a first inverter phase, and the second terminal of the winding to the next inverter phase.
  • ⁇ may be 40, 80, 120 and 160 ED.
  • the present invention is directed to a high phase order alternating current rotating machine having an inverter drive that provides more than three phases of drive waveform of harmonic order H, and characterized in that the windings of the machine have a pitch of less than 180 rotational degrees
  • the invention is a high phase order alternating current machine comprising N windings connected together in a mesh connection, driven by N phases of electrical power, where N is greater than three.
  • the windings are connected in a star or delta connection.
  • the present invention is a high phase order induction machine with short pitch windings.
  • a plurality of both odd and even order harmonics may be used to drive the machine.
  • Each harmonic may provide a different Vw, a different V/Hertz ratio, and a different chording factor.
  • both Vw and Kc affect the V/Hertz machine ratio controlling the torque output of the machine, the Vw determines the V/Hertz ratio of the windings, and the Kc determines the effective turn count of the winding.
  • the present invention teaches a method for operating a high phase order induction motor involving electrically connecting N windings into a mesh connection with a value of ⁇ that provides a substantial range in speed/torque relation when operating with at least two out of first, second and third harmonic, low order harmonics being the most efficient.
  • the pitch factor is chosen to yield a value for Kc optimized for each of the low order harmonics used, so that the Kc is reasonably close to unity and preferably helps produce the required range of speed/torque.
  • ⁇ may also be variable; if it is, the Kc is chosen at the design stage to meet an application's requirements for the usable values of ⁇ , with low order harmonics .
  • the present invention is further directed to selection of a winding pitch that yields a different value for Kc for different harmonics.
  • the aim is to select a Kc that is optimal for the desired harmonics.
  • the turn count, wire thickness, slot size, slot count and winding distribution, etc are all factors that may further affect the V/Hertz ratio. These are also optimized to provide the desired range in ratios. The machine is wound accordingly.
  • the invention further defines the following variable factors that may be used in combination to meet an application's requirements.
  • H The harmonic order, H. H must be less than N to properly develop B*H magnetic poles. In a mesh connected machine, H will affect both Vw and Kc. In addition, the lower H is, the larger is the pole area it may develop, meaning that a lower order harmonic is more powerful.
  • the winding pitch P.
  • the pitch must allow each useful harmonic to develop magnetic poles.
  • the pitch provides a different Kc ratio per allowed harmonic.
  • phase angle difference between inverter phases across each winding, ⁇ produces a different Vw per allowed harmonic.
  • ⁇ may be mechanically variable.
  • the range of possible values of ⁇ are the integers up to N/2, multiplied by 360/N.
  • V/Hertz ratios required For each application, a set of V/Hertz ratios required is determined. Values of N, H, P, ⁇ , and other factors are selected to produce the required ratios.
  • a technical advantage of the present invention is that high torque overload may be provided at low speeds whilst sufficient voltage is also provided for high-speed applications.
  • a further technical advantage of the present invention is that varying the phase angle difference across each motor phase by changing the harmonic applied by the inverter to the mesh connection, provides a change in Volts/Hz ratio through a logical change of the output synthesized by the inverter. This means that the motor may have a fixed electrical connection to the inverter.
  • a yet further technical advantage is that the change in harmonic content may be obtained in a smooth fashion, successively passing through various admixtures of harmonic components.
  • a further technical advantage of the present invention is that by changing the spanning value L, the same machine pole count is maintained.
  • Figure 1 is a diagrammatic representation of a motor stator and windings
  • Figure 2 is a diagrammatic representation of connections possible with a 9- phase polyphase device
  • Figure 3a (prior art) is a winding schematic of an 18 phase, 36 slot machine
  • Figure 3b (prior art) is a schematic of a distributed and short pitch winding in a two pole induction motor,-
  • Figure 4 is a winding schematic of a 36 slot, 36 phase machine with a short pitch winding
  • Figure 5a is a schematic of a rotor for a 34 slot machine having 17 phases
  • Figure 6a is a graphical representation of the variation in the value for Kc with harmonic drive for a range of winding pitches from 1:4 through 1:16;
  • Figure 6b is a graphical representation of the variation in Vw with harmonic drive for different values for L between 1 and 8.
  • An alternating current machine is commonly driven by an inverter.
  • An inverter is a device capable of supplying alternating current of variable voltage and variable frequency to the alternating current machine, allowing for control of machine synchronous speed and thus of machine speed.
  • the inverter may also be used with alternating current generators, and can cause an alternating current motor to act as a generator for braking applications.
  • An alternating current motor may be an induction motor, a synchronous motor with either a wound rotor or permanent magnet rotor, or a brushless DC motor.
  • a preferred embodiment of the present invention is a high phase order machine in which each phase terminal is separately connected to an inverter output.
  • the windings of the induction machine are wound with the motor terminals connected in a mesh connection to produce a low impedance output.
  • the inverter is capable of operating with a variable phase sequence that changes the effective impedance of the motor.
  • the voltage applied to a given winding which is measured from one terminal of the winding to another, will in general be different from the supply voltage fed to the machine.
  • the reason for this is that the supply will be from a machine of different connection, and thus the relevant voltage measurements will give different results.
  • Specific identified phase-to-phase voltages will always be the same for two connected high phase order machines, however the voltage placed across a winding or switching element will likely be different.
  • the following equations relate the voltage placed across the windings of a mesh connected machine to the voltages applied to the machine terminals as measured between the terminal and neutral. These are the equations which relate the output voltages of a star connected supply to the winding voltages of a mesh connected motor, and can be inverted to relate a mesh connected supply to a star connected motor. The equations could be used twice to describe a mesh connected supply connected to a mesh connected motor.
  • Equation 1 describes the line to neutral voltage of the supply, where m is the number of phases in a balanced supply, K is the particular phase of interest, and may range from 0 to m-1, ⁇ is the frequency of the alternating current in radians per unit time, t is time, h is the harmonic order being generated, and V MAX is the peak voltage of the output waveform.
  • the equation is written using standard complex exponentiation form, in which the constant e is raised to a complex number. In this case, the exponent is a purely imaginary value, thus the result of the exponentiation has constant periodicity over time. Only the real portion of this periodic function is used.
  • the terms in the exponent include a function of time, which results in the periodic nature of the voltage with time, and a constant rotation term, which results in the phase difference between the various phases .
  • each phase differs from the other phases only by the constant rotation term, and that the periodic term does not depend in any way upon the particular phase.
  • Equation 3 The voltage across the particular winding K as a function of the voltage applied to its two ends is given by Equation 3.
  • Equation 3 The voltages applied to winding K are simply that of phase K and phase K+L, where L is the spanning value for the particular mesh connection, which represents the number of inverter output phases between the first and second terminal of each single phase winding. The greater the spanning value, the greater the voltage placed upon a winding for a given inverter output voltage. Expanding Equation 3 using the terms in Equation 2 gives:
  • Equation 4 may be rearranged as follows:
  • Equation 7 is the desired result, separating the exponential term into constant and periodic portions of the various variables .
  • V MAX the periodic term
  • constant rotation term all remain as in the original equation, but an additional term is added. This term depends upon the applied harmonic h, the spanning value L 1 the number of phases m, but is independent of the particular phase K and is also independent of frequency ⁇ or time t.
  • Equation 7 shows that the voltage applied to a winding depends upon the voltage output of the supply, but it also depends upon the harmonic order h and the spanning value L. By changing the spanning value, as for example by connecting the machine using a different mesh connection, the voltage applied to the winding will change even if the voltage output of the supply remains constant.
  • the advantage of changing the harmonic applied by the inverter to the mesh connection is that the change in Volts/Hz ratio may be obtained through a logical change of the output synthesized by the inverter.
  • the motor may have a fixed electrical connection to the inverter.
  • This technique is disclosed in my co-pending application 09/713,654, filed November 15, 2000, entitled “High Phase Order Induction Machine with Mesh Connection", now U.S. Patent No. 6,657,334.
  • the change in harmonic content may be obtained in a smooth fashion, successively passing through various admixtures of harmonic components.
  • Disadvantages of this technique are that it requires a machine capable of operation with harmonic drive; e.g.
  • a pole count changing alternating current machine or a synchronous machine with variable pole count rotor, or a permanent magnet machine with a rotor which reacts both to the fundamental and the harmonic components of the drive waveform.
  • An additional disadvantage with a pole count changing alternating current machine is that the basic efficiency of such a machine will go down as the pole area is reduced. However the elimination of mechanical contactors is a benefit.
  • the advantage of changing the spanning value L is that the same machine pole count is maintained.
  • methods that change the spanning value L are applicable to machines with fixed pole counts. This includes some wound rotor alternating current machines, as well as most synchronous machines, permanent magnet machines, and brushless DC machines.
  • pole area is maintained, which increases machine efficiency.
  • changing the spanning value L generally permits a greater number of possible Volts/Hz ratios to be obtained from the same machine. Disadvantages of changing the spanning value L are that a mechanical contactor arrangement must be used to physically change the electrical connectivity of the mesh connection, and that power to the motor must be interrupted in order to change the mesh connection.
  • each phase winding set can be described by two terminals. There may be a larger number of terminals, but these are always grouped in series or parallel groups, and the entire set can be characterized by two terminals.
  • one of these terminals is driven by the inverter or power supply, while the other terminal is connected to the machine neutral point. All current flows through one terminal, through the neutral point into other windings, and though the driven terminals of the other phases.
  • these two terminals are connected directly to two different supply points.
  • N is equal to 9, but it is to be understood that this limitation is made to better illustrate the invention; other values for N are also considered to be within the scope of the present invention.
  • Figure 2a shows 9 evenly spaced terminals 4 and a center terminal 6. Each of the terminals 4 represent one end of a motor winding 1 and the center terminal 6 represents the other end of the motor winding.
  • An inverter 5 has 9 terminals 2, which are connected to one of the terminals 4 of each of the motor windings 1 via electrical connectors 3 as shown.
  • Permissible connections of the 9 phase windings are either from the center point, to each of the 9 points on the circle (this being the star connection shown as Figure 2a) or from each of the 9 points to another point. This latter is shown in Figure 2c; in Figure 2b motor winding 1 is represented by a line, and in Figure 2c inverter 5 and electrical connectors 3 have been omitted for the sake of clarity. It will be noted that for each L from 1 to 4 there is a corresponding L from 5 to 8 that produces a mirror image connection.
  • Noted on the star connection diagram are the relative phase angles of the inverter phases driving each terminal. For a given inverter output voltage, measured between an output terminal and the neutral point, each of these possible connections will place a different voltage on the connected windings.
  • the voltage across the connected windings is exactly equal to the inverter output voltage.
  • the voltage across a winding is given by the vector difference in voltage of the two inverter output terminals to which the winding is connected. When this phase difference is large, then the voltage across the winding will be large, and when this phase difference is small, then the voltage across the winding will be small.
  • the equation for the voltage across a winding is given by:
  • ⁇ is the phase angle difference of the inverter output terminals driving the winding
  • V mt is the output to neutral voltage of the inverter
  • the different mesh connections allow the motor to use the power supplied by the inverter in different rations of voltage and current, some ratios being beneficial to maximize the torque output (at the expense of available speed) , and some ratios to maximize the speed output (at the expense of maximum available torque) .
  • the inverter outputs may be represented as points on a unit circle, with the relative positions of the points representing the phase angle of this inverter output.
  • the winding of the motor is composed of individual single phase windings, each of which as two terminals.
  • the single phase windings are represented by line segments, and are the single phase sub-elements described above.
  • the end points of these line segments represent the terminals of the windings.
  • a star connection may be represented.
  • line segments are connected between points on the unit circle, then a mesh connection is represented.
  • An M phase symmetrical mesh connection will be represented by a diagram which has M fold rotational symmetry.
  • Each of the mesh connections may be represented by the spanning value "Z,' , which represents the number of inverter output phases between the first and second terminal of each single phase winding.
  • the greater the spanning value the greater the voltage placed upon a winding for a given inverter output voltage. Changes in spanning value may be considered a rotation of the connection between second terminals of each single phase winding and the inverter output terminals.
  • Harmonic drive may also be described as a multiplicative change in the power supply phase angles used to drive each winding.
  • 'H' refers to the order of the harmonic drive.
  • Full pitch windings (180 RD between supply and back windings) make most efficient use of the conductors in the slots. Concentrated windings permit maximum harmonics tolerance. Even order values of H are not useable with full pitch windings because of symmetry requirements. If even order values of H are applied to a full pitch winding, a 'magnetic short circuit' results, in which current flowing through the back half of the winding is in near opposition to the current in the supply half of the winding. The counter- flow currents cancel each other out, no magnetic field is produced, and machine inductance drops.
  • FIG. 3a a circuit diagram for a 36 slot, 36 phase, two pole, concentrated winding, full pitch machine is shown in Figure 3a.
  • Thirty-six numbered slots are provided, and the lines adjacent the slot number represent the winding in that slot. Eighteen bent lines are shown, each of which represents a driven winding phase.
  • the windings are numbered W0-W17, only the first three of which are marked, for clarity.
  • the bend in each winding renders the winding into two halves, a supply half and a back half. Depending on drive connection, either half may be the supply or back half.
  • the back half always has a phase angle difference of 180 ED from the supply half.
  • the phase angle of any given winding phase is given by equation (i) , in which H is the order of harmonic drive, W is the winding phase number and N is the phase count.
  • Each winding has a pitch of 1:19, which represents a full pitch winding and the base number of poles, B, is 2.
  • the slots containing the supply half and the back half of each phase are 180 RD apart from one another on the stator.
  • the windings are concentrated, meaning that each half winding is not distributed over more than one slot.
  • An N phase power supply supplies N voltages and currents to provide each winding with an electrical phase.
  • the high phase order machine may be provided with full bridge inverter drive, in which each winding is driven independently by two inverter half bridges. To reduce the number of inverter components by half, two approaches may be used.
  • a star connection is produced by driving one terminal of each phase winding together, while the second terminal of each winding are connected together and have a voltage of generally zero.
  • the phase angle of each winding is equal to the phase angle of the inverter drive at the driven end of each winding.
  • a mesh connection is disclosed in my previous abovementioned patents and applications.
  • Each of N windings is connected between two of N inverter outputs.
  • a first terminal of each winding phase is connected in phase angle order to one of the N inverter outputs.
  • a phase angle difference is produced by connecting the second terminal of each winding to a second inverter phase.
  • ⁇ represents the phase angle difference between the inverter output phases across the two terminals of each winding. All of the windings in a machine have the same value of ⁇ .
  • a low ⁇ is produced by connecting the first terminal of a winding to a first inverter phase, and the second terminal of the winding to the next inverter phase.
  • ⁇ may be 40, 80, 120 and 160 ED.
  • inverter output phases will supply only every second winding with electrical current.
  • a solution is to connect the windings of the first 9 odd numbered slots into a first mesh, and the windings of the first 9 even numbered slots into a second mesh.
  • the inverter phases supplied to the second mesh are offset from the inverter phases supplied to the first mesh by 360/B*N, which in the present example results in 10 ED.
  • the value of ⁇ of the 18 phase machine is equal to the value of the ⁇ of the subset mesh connections.
  • the above machine is connected with two 9 phase mesh connections, each having an ⁇ of 160 ED.
  • ⁇ in the 18 phase machine is equal to the value of ⁇ of the subsets, i.e. 160 ED.
  • the torque of a machine is commonly known to be related to the Volts/Hertz ratio.
  • the Volts referred to here is not the supply voltage Vout, but the slot voltage.
  • the slot voltage depends upon the voltage across the windings (Vw) of the machine, and may also be affected by other factors such as coil turn count, coil distribution, coil diameter, etc.
  • the voltage across each winding Vw is given by equation (ii) .
  • the voltage across mesh connected windings, Vw depends upon both ⁇ and H, which may be varied during the design stage and machine operation. Therefore, the mesh connection allows for variation in torque output without requiring voltage or frequency to be sacrificed for one another.
  • V w is 1.73*Vout
  • the machine will not function properly.
  • the odd numbered poles counted rotationally round the stator, have the same polarity as one another.
  • the first and third pole are identical.
  • the even numbered poles have the same polarity as one another, such as the second and fourth pole.
  • slots that are 180 RD apart are occupied by two halves of the same winding, and thus must operate with a 180 ED difference.
  • these conflicting requirements might result in zero current flow, or might result in a magnetic short circuit in which considerable current flows, but no magnetic field is produced.
  • an eight pole field winding halves 180 RD apart also require the same ED, but because of the full pitch winding, they are bound to a 180 ED difference.
  • a full pitch winding is one in which the two halves of each winding are a full pole distance from one another on the stator.
  • the windings are circumferentially spaced from each other by 180 RD on the stator, in a four pole motor, by 90 RD, etc.
  • full pitch windings are not in general use, since the portion of the coil going from one side of each coil to the other, the end-turns, increases the resistance of the winding without contributing to the development of torque.
  • the magnetomotive force produced by the stator winding in an ideal motor should be sinusoidally distributed.
  • a distribution factor a distribution factor
  • a skew factor a pitch factor
  • a chording factor also known as a chording factor
  • the pitch factor may perhaps best be understood with reference to a two pole machine, in which RD and ED are the same. At full pitch, one half of a given coil would be positioned in the stator core diametrically opposite the other half, i.e. the halves of the coils would be angularly displaced 180 RD about the stator. With a chorded coil of less than full pitch, one half of the coil is displaced less than 180 RD from the other half, for example, 150 RD.
  • the winding pitch may be measured in slots, eg 1:7, as a difference between slots, eg 6, in circumferential RD on the stator, eg 150 RD. Most commonly, the pitch factor is given by equation (iii) .
  • the schematic shows a distributed and short pitch winding in a prior art, three phase, two pole induction machine.
  • the four coils constituting each winding half occupy three adjacent slots. This results in a more sinusoid distribution of the phase than within the 60 RD phase belt.
  • Each coil it pitched over 5 slots, having a winding pitch of 160 RD, or a pitch factor, P, of 0.83. Note that some slots are shared by coil halves from different windings. The windings are each spread into three slots in a sequence half-full-half.
  • chording factor results from the fact that in a short pitch winding, two halves of different windings that are located in the same slot are not quite aligned with the correct current distribution. It is easiest to consider a lap winding, but the same effect generally holds for other winding types.
  • each slot holds two winding halves from different windings.
  • the net slot current depends upon the vector sum of the currents from each winding. In a short pitch winding, these two winding halves do not carry current that is in phase. So the net slot current is something less than the arithmetic sum of the two winding currents .
  • the 'Chording Factor' , Kc is given by equation (iv) .
  • Kc the net slot current is 200 amps. If the winding is short pitch, the net slot current is reduced.
  • chording factor is a multiplier to the number of actual series turns to determine the effective number of turns.
  • the 120 RD pitch windings have 10 full turns, but due to the short pitch, produce current and voltage as if they had 8.7 turns. However the length of the wire remains the same, so for resistance and resistance losses, the wire has its full 10 turns.
  • chording is that the end conductors are shorter, reducing copper and resistance. In three phase machines, chording is often used to reduce harmonic flux produced by the coils.
  • the pitch of the chorded coils is selected such that the pitch factor for the undesirable harmonics, such as the fifth and seventh harmonics is much less than that of the fundamental component.
  • a short pitch machine may be wound with an increased number of turns of thinner wire.
  • the increase in the number of turns required, and the corresponding reduction in conductor cross section, is a detriment to machine efficiency.
  • the following table highlights a low speed, high torque operating regime and a high speed operating regime.
  • the table further details trends associated with the slot voltage and current relative to the inverter output voltage and current.
  • a winding schematic is provided of a 36 slot, 36 phase machine with a short pitch winding according to the present invention.
  • the present invention is not limited to any particular number of slots or phases, and the example is given for exemplary purposes only.
  • Stator slots are numbered 1-36, representing the stator slots.
  • the lines adjacent the slots each represent the winding in that slot.
  • the 36 windings are numbered W0-W35, only a few of which are marked, for clarity.
  • Each winding is a different driven phase.
  • the bend in each winding on the diagram represents the stator end turn and renders each winding as two halves, a supply half and a back half.
  • the back half always has a phase angle difference of 180 ED from the supply half.
  • Each winding has a pitch of 1:13, which represents a short pitch winding and the base number of poles, B, is 2.
  • the slots containing the supply half and the back half of each phase are 120 RD apart from one another on the stator.
  • the windings are concentrated, meaning that each half winding is not distributed over more than one slot.
  • An N phase power supply supplies N voltages and currents to provide each winding with an electrical phase.
  • each slot contains two winding halves.
  • winding WO goes through slot 1 and returns via an end turn in the reverse direction through slot 13.
  • winding W2 goes in one direction through slot 2 and in the reverse direction through slot 14.
  • In slot 13 is one half of winding W12, the other half of which is located in slot 25.
  • Vw depends on the values of ⁇ and H.
  • the V/Hertz ratio of the machine is dependent on Vw.
  • the speed/torque output of the machine is dependent on the turn count, T, multiplied by the Kc.
  • the Kc is also dependent on H, and the winding pitch must be chosen at the design stage to have desirable characteristics with regard to the regimes in which each harmonic that is likely to be used.
  • an application requires that a very high torque be produced at low speeds, and yet high speeds should not be compromised.
  • At least two harmonics are identified, one to produce a low V/Hertz ratio and one to produce a high V/Hertz ratio.
  • a winding pitch should be chosen that has a low Kc for the harmonic with a low V/Hertz ratio. This ensures that the top speed of the high speed operating regime will not be compromised.
  • the winding pitch should have a high Kc for the harmonic that produces a high V/Hertz ratio.
  • the high Kc enables a low speed/torque ratio - and thus an effective torque boost - in the low speed, high torque operating regime.
  • each harmonic order should be matched with a Kc that meets the requirements of the application.
  • another application may require high torque at all speeds even at the expense of reaching top speeds. Therefore, a high Kc should be provided for each of the harmonic orders to be used.
  • 34 slots are provided, numbered S1-S34, of which only a sample are numbered, for clarity.
  • the windings are numbered according to winding phase order. Winding 1 is located in slots Sl and S6, Winding 2 in slots S3 and S8.
  • the back half of each winding is denoted by a minus sign.
  • Figure 6a is a graphical representation of the variation in the value for Kc with harmonic drive for a range of winding pitches from 1:4 through 1:16.
  • the Value of Kc increases to unity as the harmonic order is increased. More complex behavior is obtained at pitch numbers between 1:12 and 1:16.
  • an advantage of short pitched high phase order alternating current machines is that the chording factor may, Kc, may be varied by changing the harmonic drive.
  • the variation shown here is independent of the spanning value of the alternating current machine.
  • inverter phases V1-V17
  • Slots S1-S34 are numbered, and contain the 17 windings of Figure 5a.
  • L 6
  • Inverter phase Vl is connected to Winding 1 that has a supply-half in slot 1 and back-half in slot 6.
  • Winding 1 is also connected to inverter phase V7.
  • Winding 2 has a supply-half in slot 3 and a back-half in slot 8 and is connected to inverter phases V2 and V8.
  • Vw 1.79Vout. This Vw represents a low V/Hz ratio, and is suitable for providing high speeds. As mentioned above, the Kc is 0.45, which can more than double the speed.
  • Vw 1.60Vout and as mentioned above, a Kc of 0.8. These effects may be suited for general operation.
  • Vw 0.36Vout.
  • This harmonic produces a V/Hertz ratio suitable for reaching high torques.
  • the Kc is 0.98, which basically maintains the ratio of slot current/voltage produced by the turn count.
  • the low Vw enables very high torque to be reached at low speeds, slightly limited by the non-unitary Kc.
  • Figure 6b is a graphical representation of the variation in Vw with harmonic drive for different values for L between 1 and 8.
  • the changes shown here are independent of the winding pitch of the alternating current machine.
  • the Kc can work to maximize or mitigate the mesh effect, depending on application's requirement.
  • the range of V/Hertz ratios may be as great as 10:1.
  • a plurality of values of H can produce a wide range of Vw and Kc, and hence, V/Hertz ratios.
  • a single machine may be able to achieve both low speed torque as well as high speeds.
  • the embodiments are provided for exemplary purposes only, and should not be construed as limiting the machine to any particular combination of phases, slots, value of ⁇ , H, etc.
  • the invention further defines a number of variables a user may select in order to optimize the range of V/Hertz ratios that a machine is capable of producing. For each application, a set of V/Hertz ratios required is determined. Values of N, ⁇ , H, P, turn count, and other factors are then selected to produce the required set of ratios. The machine is assumed to be mesh connected.
  • the value of ⁇ of the mesh connection. ⁇ may be mechanically variable.
  • the values of ⁇ .allowed are the integers up to N/2 multiplied by 360/N.
  • the harmonic order of H must be less than N for proper magnetic pole development.
  • the lower H the greater is the pole area it may develop, meaning that a lower order H is more powerful.
  • the H is a factor in both the Vw and the Kc.
  • the pitch must allow each desired harmonic to develop magnetic poles.
  • the pitch provides a different Kc ratio per allowed harmonic.
  • the turn count, T must be multiplied by the Kc to produce the current to voltage ratio of the winding.
  • the slot count, size, and distribution, coil turn count, the wire diameter, the winding distribution factor, and various other factors are well known in the art in their effect on V. These effects are generally constant. These should also be selected to produce a required magnetization over the range of V/Hertz required per application. For example, in a machine in which the Kc for one of the harmonics is very low, the turn count may be increased and the wire diameter reduced, to compensate for the low Kc for that harmonic. The voltage produced by all of the harmonics will of course be decreased because of the increased turn count, and the current increased. In a further embodiment, the turn count may be usual and with regular thickness, with no compensation for the low Kc of one of the harmonics at all.
  • the machine may then be capable of operating with a very high speed/torque relation.
  • the turn count may even be reduced below normal, allowing thicker wire or other conductors, to further decrease the slot current, since in the same machine, a different harmonic can provide a high V/Hertz ratio and relatively high torque.
  • Turn counts and winding thickness are well known in the art, and are not described further here as they and their effects on current and voltage are well known. These factors may be varied for other reasons too, such as ease of winding, etc.
  • H affects the pole count and pole area and the Kc. Therefore, a small range in V/Hertz ratios may be produced by using a short pitch star connected machine and varying H.
  • PWM generation is well known in the art.
  • PWM may alternatively be provided by custom programmed logic hardware, using direct digital synthesis of the PWM waveform.
  • custom designed program control arbitrary synthesis of different waveshapes, mixtures of values of H, frequencies, and amplitudes are possible.
  • Feedback control of rotor speed or other parameters permits accurate torque/speed curves to be generated.
  • Standard winding techniques may be used and any type of wiring or conductors may form each winding phase, for example conventional inverter spike resistant wire.
  • the value of ⁇ of the mesh connection may be fixed, or alternately, all winding terminations may be brought out, permitting easy selection of different mesh connections.
  • a lap winding has been discussed; however, other types of winding may also be used with the present invention.
  • a wave winding may be used to produce the short pitch winding.
  • Using a wave winding it may be noted that the end turns on one end of the stator are substantially longer than at the other end of the stator, due to the short pitch. It is therefore recommended that every second winding be wound in a reverse direction, to even out the end turns.
  • the windings may be concentrated or distributed.
  • the pitch of the winding must have a reasonably efficient Kc for each harmonics that are chosen to drive the machine. Even a very low Kc such as 0.1 may drive the machine, but associated losses will make this undesirable. For each machine a minimum reasonable Kc must be determined for all the useful harmonics.
  • H and ⁇ are the only two variables that may be varied during operation. It should be noted that harmonics may be used in isolation or as a combination of more than one harmonics. The other variables should be optimized at the design stage for the most useful values of H and/or ⁇ .
  • the machine is wound with the selected values of N, P and T.
  • a value of ⁇ is selected with which the windings are electrically connected to the inverter.
  • the machine is driven with one of the selected values of H.
  • a change in speed/torque relation is produced by mechanically varying ⁇ and/or electrically varying the value of H or superimposing various values of H.
  • a winding that contains a plurality of coils may have different coils of different pitch, for example each winding has a first coil 1:6 and a second coil 1:7.
  • the machine may be wound with any pole count.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Windings For Motors And Generators (AREA)
  • Control Of Ac Motors In General (AREA)

Abstract

L'invention concerne une machine rotative à courant alternatif à ordre de phase élevé qui est dotée d'une commande de convertisseur qui produit au moins trois phases de forme d'onde de commande d'ordre harmonique H, et qui se caractérise en ce que les enroulements de la machine ont un pas inférieur à 180 degrés en rotation. De préférence, les enroulements sont reliés ensemble en connexion polygonale, en étoile ou en delta. L'invention concerne également un procédé permettant de commander un moteur à induction à ordre de phase élevé, qui consiste à relier électriquement N enroulements dans une connexion polygonale avec une valeur de Δ qui produit une gamme importante en matière de relation vitesse/couple lors du fonctionnement avec au moins deux des premier, deuxième et troisième harmoniques, les harmoniques d'ordre inférieur étant les plus efficaces.
EP05762757A 2004-06-21 2005-06-21 Machine ca a ordre de phase eleve a enroulement a pas court Withdrawn EP1805888A2 (fr)

Applications Claiming Priority (2)

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US58178904P 2004-06-21 2004-06-21
PCT/US2005/022011 WO2006002207A2 (fr) 2004-06-21 2005-06-21 Machine ca a ordre de phase eleve a enroulement a pas court

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WO2006065988A2 (fr) 2004-12-13 2006-06-22 Borealis Technical Limited Enroulements d'un moteur
US7126298B2 (en) 2000-10-23 2006-10-24 Borealis Technical Limited Mesh connected brake array for electrical rotating machines
US7928683B2 (en) 2000-10-23 2011-04-19 Borealis Technical Limited High phase order AC machine with short pitch winding
US8532957B2 (en) 2000-11-15 2013-09-10 Borealis Technical Limited Aircraft weight estimation method
US8198746B2 (en) 2000-11-15 2012-06-12 Borealis Technical Limited Chimney turbine
US7469858B2 (en) 2003-10-09 2008-12-30 Borealis Technical Limited Geared wheel motor design
US8712603B2 (en) 2004-08-17 2014-04-29 Borealis Technical Limited Aircraft drive
GB2439247B (en) 2005-03-01 2010-06-30 Borealis Tech Ltd Motor controller
GB2440872B (en) 2005-04-19 2010-08-18 Borealis Tech Ltd Induction and switched reluctance motor
US7891609B2 (en) 2006-08-29 2011-02-22 Borealis Technical Limited Turnaround methods
GB0617068D0 (en) 2006-08-30 2006-10-11 Borealis Tech Ltd Transistor
US8220740B2 (en) 2007-11-06 2012-07-17 Borealis Technical Limited Motor for driving aircraft, located adjacent to undercarriage wheel
PT104152A (pt) * 2008-08-01 2010-02-01 Univ Nova De Lisboa Motor polifásico com número de pólos variáveis
US8849480B2 (en) 2013-03-01 2014-09-30 Honeywell International Inc. Aircraft gross weight and center of gravity validator
WO2018050846A1 (fr) * 2016-09-18 2018-03-22 Seva Academy Ltd. Machine comportant un entraînement à vitesse de rotation variable pour produire un courant continu

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US6657334B1 (en) * 2000-10-23 2003-12-02 Borealis Technical Limited High phase order motor with mesh connected windings
US6054837A (en) * 1994-06-28 2000-04-25 Borealis Technical Limited Polyphase induction electrical rotating machine

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GB0701138D0 (en) 2007-02-28
GB2430086A (en) 2007-03-14
AU2005258106A1 (en) 2006-01-05
WO2006002207A2 (fr) 2006-01-05
GB2430086B (en) 2008-01-30
WO2006002207A3 (fr) 2006-10-05

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