Drive wave form synchronization for induction motors
First Claim
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1. An electrical induction machine comprising:
- a n phase order induction motor in which n is greater than three;
a controller for synthesizing an alternating current having n phases, said alternating current inducing a first rotating magnetic field in windings of said motor, wherein said current is derived using pulse width modulation having a fixed number of pulses per cycle, said fixed number being less than n;
wherein the timing and duration of said pulses is selected so that distortion in said current produces a second rotating magnetic field in said motor that is synchronous with said first rotating magnetic field.
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Abstract
A polyphase induction motor is operated by an inverter drive system comprising a logic level controller. A number, preferably twelve or more, of independently driven phases causes harmonic fields, up to a number equal to the number of phases, to oscillate in synchrony with the fundamental oscillating field. A pulse-width modulation (“PWM”) carrier is used by the logic level controller to synthesize a desired drive alternating current, in which the pulsing distortion produced by the pulse width modulation produces a synchronous oscillating field in the driven polyphase induction motor.
62 Citations
27 Claims
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1. An electrical induction machine comprising:
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a n phase order induction motor in which n is greater than three;
a controller for synthesizing an alternating current having n phases, said alternating current inducing a first rotating magnetic field in windings of said motor, wherein said current is derived using pulse width modulation having a fixed number of pulses per cycle, said fixed number being less than n;
wherein the timing and duration of said pulses is selected so that distortion in said current produces a second rotating magnetic field in said motor that is synchronous with said first rotating magnetic field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A drive system comprising:
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electronics for synthesizing an alternating current having n phases to operate a n phase order induction machine in which n is greater than three, wherein said current is derived using pulse width modulation having a fixed number of pulses per cycle, said fixed number being less than n;
wherein the timing and duration of said pulses is selected so that distortion in said current produces a rotating magnetic field in said motor that is synchronous with the primary rotating magnetic field developed in said motor;
a logic level controller to provide pulse-width modulation signals to said electronics. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for producing a synchronized drive waveform for a n phase order induction machine in which n is greater than three, comprising the steps of:
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supplying electrical power from a DC power supply to n half-bridge circuits, wherein each of said half-bridge circuits comprises a positive switching element connected to a positive rail of said DC power supply and a negative switching element connect to a negative rail of said DC power supply;
operating said switching elements according to an input control logic signal, wherein said control logic signal is a periodic waveform generated by a pulse-width modulation technique;
outputting a drive waveform at each half-bridge to drive each phase, wherein said drive waveform is displaced in time by a phase angle that is equal to a physical angle of a winding in a stator;
synthesizing an alternating current having n phases, wherein said current is derived using pulse width modulation having a fixed number of pulses per cycle, said fixed number being less than n;
wherein the timing and duration of said pulses is selected so that distortion in said current produces a rotating magnetic field in said motor that is synchronous with the primary rotating magnetic field developed in said motor. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification