单项选择题
The frequency of the alternating current generated by a synchronous generator is governed by the speed and the（）
A.full excitation B.load C.power factor D.number of poles
单项选择题 When two DC generators operate in parallel, they are protected against motorizing by（）
单项选择题 The correct phase rotation of a three-phase alternator can be checked with a（）
单项选择题 A probable cause for a turbo generator tripping out on overspeed is a sudden（）
