单项选择题
A.brushes B.slip rings C.commutators D.all of the above
It （） for an emergency generator to require paralleling...
单项选择题It （） for an emergency generator to require paralleling.
A.is usual B.is not usual C.is necessary D.is not impossible
Usually the panels are interlocked with （） so that the ...
单项选择题Usually the panels are interlocked with （） so that the devices can be made dead before the doors are opened.
A.protective earth B.isolators C.ground switch D.circuit-breakers
In （） the control action is independent on(of) the outp...
单项选择题In （） the control action is independent on(of) the output.
A.a closed loop control system B.an open loop control system C.a boiler control system D.a steering gear control system
