單項(xiàng)選擇題An alternator switchboard has a synchroscope and synchronizing lamps, if the synchroscope is broken, which of the steps listed is the most essential before an alternator can be paralleled with the bus （）

A.The breaker should be closed when one synchronizing lamp is dark and the other is bright
B.The breaker should be closed when both synchronizing lamps are bright
C.The frequency meter should be used to determine that the incoming alternator frequency is slightly higher than the bus
D.A portable phase sequence indicator must be used to verify the information from the lamps


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2.單項(xiàng)選擇題The energy consumed by an AC motor, as strictly reactive power, is （）

A.used to do mechanical work
B.used to establish the magnetic field of the motor
C.lost as heat generated by the windings
D.lost in doing work to turn the motor itself

3.單項(xiàng)選擇題A diesel driven emergency generator is prevented from being paralleled with the ships service generators by （）

A.an electrical interlock system
B.an automatic paralleling trip switch
C.the synchronizing oscilloscope
D.the reverse current relay

4.單項(xiàng)選擇題A motor enclosure which protects against falling liquids is classified as （）

A.waterproof
B.drip proof
C.spray tight
D.spray proof

5.單項(xiàng)選擇題Universal motors will operate on AC or DC current, and are generally found in （）

A.portable tools
B.large pump motors
C.turbo electric main motors
D.forced draft fans