The overcurrent relay （） the motor contactor when the motor exceeds its rated current.

In a modern three-phase A-Csynchronous brushless generator, the excitation winding is on the rotorThat means （）.

A.The generator needs not excitation
B.The winding on the rotor is for inputting excitation current
C.There are three phase windings on the rotor
D.The generator has brushes

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Ammeter is to measure the （）.

A.current
B.voltage
C.power
D.frequency

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