单项选择题

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

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单项选择题

“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

单项选择题

The nameplate of an AC non-synchronous motor shows that running speed is 1460r/minfrequency 50HzYou can infer that the number of magnetic poles is（）

A.2
B.4
C.6
D.8

单项选择题

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