單項(xiàng)選擇題The DC excitation to the field of brushless synchronous is generally produced by ()

A.an exciter driven by the same shaft with the generator
B.an exciter driven by external prime mover
C.generator itself
D.either A and B


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1.單項(xiàng)選擇題Which of the following equipment is not pollution prevention equipment?()

A.oily water separator
B.sewage treatment plant
C.fuel oil separator
D.incinerator

2.單項(xiàng)選擇題The initial voltage of self-excitation generator set up by()

A.residual magnetism
B.voltage regulator
C.electrical current for excitation
D.the other running generator

3.單項(xiàng)選擇題“380V/220V Y/△” noted on the nameplate of a non-synchronous motor means that()

A.the armature terminals of the motor should be connected in star formation when voltage of power supply is 380
B.the armature terminals of the motor should be connected in star formation when voltage of power supply is 220
C.both A and B are correct
D.the armature terminals of the motor should be connected in reverse ways of A and B

5.單項(xiàng)選擇題With one or more cylinders out of operation, the engine speed must be reduced because()

A.in such cases, the air supply is no longer optimal, the thermal load will be higher
B.governor hunting will occur
C.torsional vibrations as other mechanical vibrations may occur
D.all of the above are correct