單項(xiàng)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


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1.單項(xiàng)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

3.單項(xiàng)選擇題The unit "hertz" is equivalent to （）

A.coulombs per second
B.revolutions per second
C.revolutions per minute
D.cycles per second

4.單項(xiàng)選擇題When paralleling two AC generators, the frequency of the machine coming on-line, immediately prior to closing its breaker, should be （）

A.slightly less than the oncoming generator frequency
B.the same as the bus frequency
C.slightly greater than the bus frequency
D.the same as the bus voltage

5.單項(xiàng)選擇題When two AC generators are being paralleled, the breaker should be closed with the synchroscope pointer mating in the （）

A."slow" direction, just before the 12 o'clock position
B."fast" direction, just after the 12 o'clock position
C."fast" direction, just before the 12 o'clock position
D."slow" direction, just after the 12 o'clock position