| 摘要 |
A winding of a brushless permanent-magnet motor is commutated at times that are retarded relative to zero-crossings of back EMF in the winding when operating at speeds greater than 50 krpm. Commutation can be retarded when operating over speed range spanning at least 5 krpm. A commutating retardation period can be varied in response to a winding excitation supply voltage or the speed of the motor. The retard period can increase with an increase of the supply voltage and/or a decrease in speed. An electrical half cycle can be divided into a conduction period, when the winding is excited, followed by a freewheel period. The conduction period can be further divided into an excitation period, a second freewheel period and a further excitation period. Commutation can be advanced when operating at a higher speed range, using higher power, than a range over which it is retarded, using constant power. The high speed range and the low speed range can each span at least 5 krpm. |
