单项选择题
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
单项选择题 Moisture absorbed in the windings or condensed on the surface of electrical machinery insulation （）
单项选择题 When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is （）
单项选择题 While paralleling two AC generators using synchronizing lamps only, both lamps will go dark when the generators are （）.