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


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2.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

3.單項(xiàng)選擇題

A few spots of turbocharger can be caused by（）
①crash stop of engine
② rapid increased of engine speed

A.①only is correct
B.②only is correct
C.both ① and ②are correct
D.neither ① or ② correct

4.單項(xiàng)選擇題The function of synchronous compensating machine is to（）

A.improve power factor
B.reduce voltage oscillation
C.increase the insulation of circuits
D.eliminate regenerated magnetic fields

5.單項(xiàng)選擇題What is head tank in the closed cooling water system used for?（）

A.for the release of air from the cooling water
B.providing expansion room for heated cooling water
C.a place for implementing water and water treatment agent
D.all of the above