單項選擇題Prior to closing the breaker when paralleling two AC generators, the recommended practice is to have the frequency of the incoming machine ()

A.slightly less than the line frequency
B.the same as the line frequency
C.slightly greater than the line frequency
D.All of the above


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1.單項選擇題Which of the following should be the FIRST step in removing a generator from parallel operation?()

A.Trip the generator off the switchboard
B.Turn off all electrical equipment
C.Remove the load from the "off going" generator
D.Increase the cycles of the generator staying on the line

2.單項選擇題Electrical power is expressed in ()

A.ohms
B.volts
C.amps
D.watts

3.單項選擇題Which of the following materials is a good insulator?()

A.steel
B.aluminum
C.glass
D.copper

4.單項選擇題To protect the rotor of a motor disassembled for maintenance or overhaul, it should be()

A.suspended by wire slings in one comer of the shop
B.wrapped in several layers of heavy paper or carboard
C.supported by flat wood blocks on the workbench
D.returned to the frame as soon as the bearings are removed

5.單項選擇題When paralleled, AC generators must have the same ()

A.frequency
B.number of phases
C.phase rotation
D.All of the above