單項(xiàng)選擇題

Some large A-Cmotors are equipped with heatersThese could be ()
(1)resistance heaters bolted directly to the frame
(2)low voltage windings embedded in the motor windings

A.(1) only
B.(2) only
C.either (1) or (2)
D.neither (1) or (2)


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1.單項(xiàng)選擇題

In order to change the direction of rotation of a D-Cmotor ()
(1) the field leads must be changed
(2) the input leads must be changed

A.(1)only
B.(2)only
C.either(1)or(2)
D.neither(1)or(2)

2.單項(xiàng)選擇題

If a small electric motor is immersed in salt water it should be ()
(1) washed in fresh water
(2) dried in an oven

A.(1) only
B.(2) only
C.both (1) and (2)
D.neither (1) or (2)

3.單項(xiàng)選擇題The unit of electrical power is the ()

A.ampere
B.kilovolt
C.watt
D.farad

4.單項(xiàng)選擇題In an alternating current electrical system, a low system power factor is a direct sign of ()

A.wasted energy
B.efficient operation
C.a short in the exciter field windings
D.an excessive number of minor system grounds