单选题Prior to closing the breaker when paralleling two AC generators, the recommended practice is to have the frequency of the incoming machine （）Aslightly less than the line frequencyBthe same as the line frequencyCslightly greater than the line frequencyDAll of the above
单选题
Prior to closing the breaker when paralleling two AC generators, the recommended practice is to have the frequency of the incoming machine （）
A
slightly less than the line frequency
B
the same as the line frequency
C
slightly greater than the line frequency
D
All of the above
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