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
  • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
  • H02P6/14—Electronic commutators
  • H02P6/16—Circuit arrangements for detecting position
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K23/00—DC commutator motors or generators having mechanical commutator; Universal AC/DC commutator motors
  • H02K23/62—Motors or generators with stationary armatures and rotating excitation field
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K25/00—DC interrupter motors or generators

Definitions

• the present invention relates to Rotating Electric Machines that operate as either motors or generators.
• Multiphase permanent magnet brushless motors are extremely versatile and efficient machines offering superior control and efficiency compared with AC synchronous and PM DC motors in many different applications.
• end users require the compactness, high efficiency and long life of a brushless motor but without the high cost of the drive and control electronics required to operate the brushless motor. Too often these costs force end users to settle for an inferior class of motor.
• the commutator further includes three brushes spatially located 120 degrees apart about the commutator and connected to windings of a motor, wherein during rotation of the commutator the commutator segments and freewheeling segments alternately engage with the three brushes connected to the windings.
• the drive means includes a first gear fixed to the output shaft and a second gear fixed to a commutator shaft and meshed with the first gear.
• the drive means includes a first gear fixed to the output shaft, a second gear fixed to a commutator shaft and a chain or belt transmitting rotary motion from the first gear to the second gear.
• the machine further includes idler rollers engaging the chain or belt .
• the drive means includes a motor coupled to a shaft of the commutator and arranged to operate at the second speed N2.
• the motor is one of a mechanically commutated DC motor, a permanent magnet DC motor or a brushless DC motor.
• the machine is one of a synchronous DC motor, an asynchronous AC motor or a synchronous AC reluctance motor.
• the machine further includes an electronic chopper for one or more of regulating speed, improving commutation or affecting phase advance.
• the switch is also connected to the winding.
• n is an integer greater than 1.
• the machine is an automotive alternator.
• Figure 1 is an exploded view of the mechanical commutation device described above and below.
• Figure 2 is a view of a machine with a commutator mechanically connected by a gear drive.
• Figure 3 is a view of a machine with a commutator mechanically connected by a chain or belt drive.
• Figure 4 is a view of a machine with a commutator mechanically connected by a chain or belt drive, with the addition of movable idler rollers to effect phase advance for greater control of the machine.
• Figure 5 is a view of a machine comprising a driven motor, a separate driving motor, and the mechanical commutation device.
• Figure 6 is a view of a second embodiment of a machine comprising a driven motor, a separate driving motor, and the mechanical commutation device.
• Figure 7 is a view of a further embodiment of a machine comprising a driven motor, a separate driving motor, and the mechanical commutation device.
• Figure 8 is a waveform graph showing how variations in the voltage of a chopper circuit could improve commutation.
• Figure 9 is a waveform graph showing how variations in the voltage of the chopper circuit, or the speed of the driving motor, may effect phase changes.
• the central insight governing the invention is that a 2- or 4-pole commutator can drive a machine with a much larger number of poles, provided it can be made to rotate at an appropriate multiple of the speed of the driven motor. (For example, if a 2-pole commutator is to drive an 8-pole machine, the commutator must rotate at four times the speed of the driven machine.)
• the various aspects of the invention describe various means of achieving this, both by mechanically connecting the commutator to the motor, and by the use of a second, smaller motor to drive the commutator. In the first case, the result is a radical reduction in the minimum size, complexity and cost of the commutator for multi-pole machines, as compared to previous embodiments.
• a single commutator may be used to drive two or more driven motors, either synchronous (DC) or asynchronous (AC) . This may have a number of applications in industry (e.g. conveyors) .
• Figure 1 illustrates individual components of a basic 2- pole mechanical commutation device, comprising: A commutator base 1, a positive slip-ring 2 and a negative slip-ring 3, each having a continuous conducting circular perimeter 46, 47, a positive electrically conductive commutator segment 48 electrically connected to the positive slip-ring 2 and a negative electrically conductive commutator segment 49 electrically connected to the negative slip-ring 3, and first and second freewheeling segments 4, 5 electrically isolated from the commutator segments 48, 49 and interspersed at respective positions between the commutator segments, and a first diode 6 between the negative commutator segment 49 and the first freewheeling segment for allowing current flow only from the negative commutator segment 49 to the first freewheeling segment 4, and a second diode 7 between the positive commutator segment 48 and the second freewheeling segment 5 for allowing current flow only from the second freewheeling segment 5 to the positive commutator segment 48.
• the commutation elements and freewheeling segments 4, 5 are separated by insulation rings 8, 9.
• the commutator components are fixed to the base 1 by two fixing screws 12, 13.
• the fixing screws 12, 13 are located within isolating sleeves 14, 15 to prevent short-circuit of the commutator components.
• the commutator further includes three brushes (not illustrated) spatially located 120 degrees apart about the commutator and connected to windings of a motor, wherein during rotation of the commutator the commutator segments and freewheeling segments alternately engage with the three brushes connected to the windings.
• three brushes (not illustrated) spatially located 120 degrees apart about the commutator and connected to windings of a motor, wherein during rotation of the commutator the commutator segments and freewheeling segments alternately engage with the three brushes connected to the windings.
• FIG 2 illustrates an embodiment of the machine according to the first aspect of the invention.
• the motor 14 has a gear 15 mounted on its shaft. This meshes with a second gear 16 which is connected by a separate shaft to the mechanical commutation device 17, which in turn is connected electrically by wires 18 to the motor 14.
• the gear 15 may employ axial rather than radial gearing, and thus may drive a shaft instead of another gear.
• the mechanical commutation device 17 may be mounted at the end of the shaft .
• the shaft may be either straight or flexible.
• Figure 3 shows another embodiment of the machine according to the first aspect of the invention.
• the motor 18 has a gear 19 mounted on its shaft. This is connected to a second gear 20 by a chain or belt 21 which is connected by a separate shaft to the mechanical commutation device 22, which in turn is connected electrically by wires to the motor 18.
• FIG. 4 shows another embodiment of the machine according to the first aspect of the invention.
• the motor 23 has a gear 24 mounted on its shaft. This is connected to a second gear 25 by a chain or belt 26 which is connected by a separate shaft to the mechanical commutation device 27, which in turn is connected electrically by wires to the motor 23.
• Two movable idler rollers 28, 29 are positioned on either side of the belt or chain drive 26 such that moving them may alter the phase relationship between gears 24 and 25. This enables the phase relationship between the motor 23 and the mechanical commutation device 27 to be altered, thus enabling phase variations without the need to employ electronics.
• FIG. 5 illustrates an embodiment of the machine according to the second aspect of the invention.
• the driven motor 30, which may be either a DC synchronous, AC induction or synchronous AC reluctance machine is electrically connected to the mechanical commutation device 31.
• the drive motor 32 which may be either a PMDC machine, brushless DC machine, or a machine employing a mechanical commutator device as described above.
• the use of a brushless DC machine to drive this arrangement may be very cost-effective if the driven motor is of a high power rating.
• the cost of power electronics for brushless DC motors rises exponentially as the motor's power rating is increased. Therefore the use of a much smaller brushless motor, which only needs to effect rotation of the mechanical commutator at the desired speed, will provide all the control advantages associatd with brushless DC motors at substantially reduced cost.
• FIG. 6 illustrates another machine according to the second aspect of the invention.
• This machine is a combined motor-generator, of a type suited to automotive starter- alternators.
• alternators are usually geared up to run at 2.5-3 times the speed of the engine. For short bursts of acceleration, engine speeds of up to 6,000-7,000 rpm are not uncommon. This leads to an alternator speed of over 20,000 rpm, which if connected to the mechanical commutation device would result in reduced lifespan due to frictional wear.
• the machine shown in figure 6 ameliorates this problem.
• a driven motor-alternator 34 is electrically connected to a start control 35, and a rectifier 36.
• a rectifier a device familiar to those skilled in the art, consists of 6 diodes, 2 per phase, connected so as to reverse the voltage during the negative half cycle of the AC waveform so that a DC output is obtained. These 6 diodes are mounted on heat sinks at the non-drive end of the alternator and are cooled by the air entering the alternator due to internal fans on the rotor.
• An auxiliary drive motor 37 is mechanically connected to the mechanical commutation device 38 described above.
• Separate supplies, 39, 40 are connected to the drive motor 37 and the mechanical commutator 38 respectively.
• the supplies 39, 40 are energised, thus enabling the machine to operate as a motor.
• the supplies 39, 40 are disengaged. This enables the driven machine 34 to operate as a generator, employing the rectifier 36, without the mechanical commutation device 38 being driven, thus increasing its lifespan.
• an alternative method of connecting either the mechanical commutator 38 to the rectifier 36, the 3 phase stator windings may be permanently connected to both the mechanical commutator 38 brushes and to the rectifier 36 but may use a switch 42 to switch the DC input from the battery 41 either to the mechanical commutator 44 input brushes on the slip rings or to the rectifier 45 output.
• this may only involve switching from 1 contact to another.
• it would be necessary to ensure that 2 phase brushes could not connect to one commutator bar so, depending on brush width, the arc of a commutator bar would need to be less than 120 degrees - about 100 degrees and the arc of the neutral would be increased from 60 degrees to 80 degrees.
• the auxiliary motor 37 may be stopped (or run at low speed in stand by mode) whenever the starter-alternator was operating as a generator or alternatively whenever the alternator speed exceeded say 6000 rpm. The latter would allow the mechanical commutator 38 to control phase advance and obtain improved generated output at lower speeds when required.
• the dc supply includes a chopper (power electronic chopper) .
• a chopper power electronic chopper
• Such devices are familiar to those skilled in the art. Such devices are much cheaper than inverters used in standard brushless motors, because they have fewer power devices (1 instead of 6) although the single device has a higher current rating than each of the 6 devices.
• the volt amp rating will be l/3 rd or less and only 1 device has to be mounted on a heat sink. (There is only 1 freewheeling diode compared with 6 for the inverters) .
• the power electronic chopper may also provide improved commutation by switching off the voltage (and, hence, reducing the current) at or just before each switching event of the mechanical commutator. This may further reduce arcing, which is minimal to begin with in this design, thus further increasing the lifespan of the machine.
• Figure 8 illustrates the effect of switching off the voltage at the point of commutation.
• a position sensor such as a Hall effect device, familiar to those skilled in the art, may be used to define the switching positions or the onset of commutation may be detected by a voltage/current sensor in the DC supply or in each phase.
• auxiliary motor driven commutator may provide phase advance.
• the auxiliary motor position may be adjusted to provide phase advance because it is driven independently of the main motor.
• a separate voltage supply to the auxiliary motor may adjust the speed and, hence, position of the motor and the mechanical commutation device which may advance the position at which switching takes place.
• the auxiliary motor is much smaller than the main motor, its response will be much more rapid, allowing it to be speeded up and down for each phase in turn.
• the Power Electronic Chopper may be used to adjust the voltage to each phase in turn, providing a much more rapid adjustment. This may provide a higher voltage at the start of each phase i.e. giving phase advance in effect.
• Figure 9 illustrates the waveform effect of applying a higher voltage to each phase in turn.
• Either rotor position sensors such as Hall effect devices, may be used to provide main rotor position - or at lower cost - a voltage signal from each phase may provide position signals.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
• Dc Machiner (AREA)

Applications Claiming Priority (3)

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• 2005
  • 2005-12-16 EP EP05818530A patent/EP1869750A1/de not_active Withdrawn
  • 2005-12-16 WO PCT/IB2005/003797 patent/WO2006064354A1/en active Application Filing
  • 2005-12-16 JP JP2007546220A patent/JP2008524979A/ja active Pending

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