Importance

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Abstract

In a plural phase electric motor, a control system provides a variable commutation delay interval between commutations from state to state, during which delay interval all phases are unenergized, to minimize current spikes upon commutation. The duration of the delay interval is varied according to a given motor operating parameter during operation of the motor to optimize the delay interval for different operating conditions, to provide maximum delay when needed to eliminate current spikes, and to provide minimum delay when unneeded, to in turn provide maximum energization current to the phases. In one embodiment, motor speed is sensed, and the duration of the delay interval is varied in response thereto by shortening the delay interval with increasing motor speed. In another embodiment, DC bus current is sensed, and the duration of the delay interval is varied in response thereto by preventing termination of the delay interval until the level of DC bus current drops below a given value.

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First Claim