单项选择题The primary function of an electric motor is to ()

A.develop torque
B.generate high voltages
C.produce a magnetic field
D.generate high electrical resistance


您可能感兴趣的试卷

你可能感兴趣的试题

1.单项选择题The power factor at which a paralleled AC generator operates is usually adjusted by the ().

A.connected load
B.prime mover speed
C.field excitation
D.generators rated voltage

3.单项选择题Equal power factors on paralleled AC generators are maintained by an automatic ().

A.voltage regulator
B.reverse power relay
C.reverse current relay
D.governor control switch

4.单项选择题To equalize the power factor of two alternators operating in parallel, the ()

A.field excitation of both units is adjusted
B.governors of both units are adjusted
C.phase sequence is altered
D.kilowatt load is evenly divided

5.单项选择题An advantage of DC motors over AC motors is that they ()

A.are less expensive
B.require less maintenance
C.can be started across the line
D.offer a more effective means of controlling speed

6.单项选择题Which of the following devices are protected from being motorized by a reverse-power relay?()

A.Alternators
B.Wave guides
C.Exciters
D.Amplidynes

8.单项选择题AC and DC generators are similar in that they ()

A.both generate alternating voltages
B.both rectify the voltage before delivery
C.are constructed at the same physical size for the same kilowatt rating
D.both supply three-phase power

9.单项选择题To increase the frequency of an operating AC generator, you should ()

A.increase the field excitation
B.decrease the field excitation
C.increase the number of magnetic poles
D.increase the speed of the prime mover

10.单项选择题When measuring AC current flow, you must always connect the meter ()

A.in series with the power source and load
B.in parallel with the power source and load
C.insuring correct polarity
D.using the lowest range possible to prevent instrument damage