單項(xiàng)選擇題

The purpose of a main switchboard circuit breakers reverse-power trip is to （）.

A.prevent main circuit overload
B.protect the circuit breaker blowout coil
C.prevent alternator motorization
D.prevent low voltage tripout

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單項(xiàng)選擇題

When you are making a high potential test on a piece of repaired electrical machinery, a rise in leakage current indicates （）.

A.good insulation
B.bad insulation
C.high insulation power factor
D.a high slot discharge factor

單項(xiàng)選擇題

The sub-multiple prefix "milli" (m) means （）.

A.one thousandth (10 to the -3rd power)
B.one millionth ( 10 to the -6th power)
C.one billionth ( 10 to the -9th power)
D.one trillionth (10 to the -12th power)