题目内容

A three-phase asynchronous induction motor running in a three-phase insulated ship power system, only the stator single-phase winding and the grounded shell are short-circuited accidentally, then ( ).

A. fuses will blow out
B. thermal relay will act
C. not affected
D. large grounded current will occur

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Protection that cannot be done by air circuit breaker alone is ( ).

A. undervoltage protection
B. overload protection
C. reverse power protection
D. short circuit protection

In the contacts system of generator main switch on the distribution board, the contacts used to connect and disconnect the power grid is ( ).

A. main contacts only
B. main / auxiliary / arc contacts
C. main contacts / secondary contacts / arc contacts
D. main contacts / auxiliary contacts

For the frame-type automatic air circuit breaker, if we can move the handle but cannot be closed, we should check ( ) first.

A. energy storage switch
B. contact of relay
C. arc-extinguishing grid
D. undervoltage tripping device

The arc extinguishing grid of the automatic air circuit breaker is made of ( ).

A. insulation material
B. iron grid
C. ceramic material
D. hard rubber

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