单项选择题
The operation of paralleling two alternators requires the voltages to be （）and also in phase.
A.zero
B.eliminated
C.different
D.equal
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The （） is a measure of the phase difference between voltage and current and is expected as the cosine of phase angle.
A.power
B.efficiency
C.effective power
D.power factor -
单项选择题
The overcurrent relay （） the motor contactor when the motor exceeds its rated current.
A.connects
B.trips
C.fouls
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单项选择题
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
