| 摘要 |
The drive circuit has a pair of windings associated with each phase of the motor, with the windings of each pair being connected in antiphase. The circuit comprises a d.c. supply, respective semiconductor switches in series with each motor winding for supplying current from the supply to the associated winding in only one direction, and frequency control circuitry for switching the switches on and off so as to cause the windings of each winding pair to conduct current alternately and in opposite directions at a frequency which may be varied so as to vary the speed of the motor. In this arrangement there is no possibility of a short circuit path occurring which does not incorporate one of the motor windings, so that the rate of rise of fault current is finite and over-current detection circuitry can be used to turn off the switches or operate a crowbar.
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