单选题The voltage output of an AC generator is controlled by（）Avarying the DC exciter voltageBvarying the reluctance of the air gapCregulating the speed of the prime moverDshorting out part of the armature windings
单选题
The voltage output of an AC generator is controlled by（）
A
varying the DC exciter voltage
B
varying the reluctance of the air gap
C
regulating the speed of the prime mover
D
shorting out part of the armature windings
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