单项选择题

The most common source of excitation for synchronous motors is a/an （）.

A.low voltage battery
B.motor attenuator set
C.DC exciter generator
D.AC supply

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单项选择题

Before reassembling any machinery, you should （）.

A.replace all bearings regardless of length of service
B.apply a heavy coat of oil to all mating surfaces
C.clean any corroded surfaces and file all burrs smooth
D.coat all parts with alemite grease

单项选择题

Ammeters and voltmeters used in sinusoidal AC power systems indicate which of the following values of the waveforms measured?（）

A.Peak value
B.Root-mean-square value
C.Average value
D.Maximum value