单项选择题
The correct phase rotation of a three-phase alternator can be checked with a（）
A.dynamometer B.power factor meter C.three-phase motor D.polyphase voltmeter
单项选择题 A probable cause for a turbo generator tripping out on overspeed is a sudden（）
单项选择题 All of the following operating characteristics are listed on the name-plates of motors used aboard ship except the（）
单项选择题 When would you ground an electric hand tool?（）
