單項(xiàng)選擇題The correct phase rotation of a three-phase alternator can be checked with a（）

A.dynamometer
B.power factor meter
C.three-phase motor
D.polyphase voltmeter


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1.單項(xiàng)選擇題A probable cause for a turbo generator tripping out on overspeed is a sudden（）

A.loss of field excitation
B.total loss of load
C.large increase in load
D.loss of steam pressure

2.單項(xiàng)選擇題All of the following operating characteristics are listed on the name-plates of motors used aboard ship except the（）

A.temperature rise
B.input kilowatts
C.horsepower
D.operating voltage

3.單項(xiàng)選擇題When would you ground an electric hand tool?（）

A.When it is a DC machine
B.When it is an AC machine
C.Any machine that operates on over 100 volts
D.Only when working on wet steel plates

4.單項(xiàng)選擇題The load between two steam-driven alternators operating in parallel may be adjusted by varying （）

A.the speed of the alternators
B.the field strength of the machines
C.the power factor of the alternators
D.steam supply to the prime movers

5.單項(xiàng)選擇題The purpose of the commutator and brushes on a DC generator is to（）

A.change AC to DCcurrent
B.change DC to AC current
C.neutralize a armature reaction
D.carry current to the outside circuit