单选题The voltage developed by an AC generator is controlled by varying the （）Aspeed of the prime moverBAC excitation to the fieldCDC excitation to the fieldDDC excitation of the voltage regulator
单选题
The voltage developed by an AC generator is controlled by varying the （）
A
speed of the prime mover
B
AC excitation to the field
C
DC excitation to the field
D
DC excitation of the voltage regulator
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