单项选择题
A.penetration of moisture B.accumulation of dirt C.overheating D.All of the above
A three-phase alternator operates at 450 volts with a p...
单项选择题A three-phase alternator operates at 450 volts with a power factor of 0~8.If the ammeter indicates 250 amperes, what should be the KW meter reading （）.
A.90~0 kw B.127~27 kw C.155~70 kw D.194~85 kw
Sparking at the brushes of a running motor could be an ...
单项选择题Sparking at the brushes of a running motor could be an indication of （）.
A.normal operation B.a dirty commutator C.increased brush capacity D.water vapor absorption
If a DC motor runs hot, the cause may be （）A.high mica ...
单项选择题If a DC motor runs hot, the cause may be （）
A.high mica condition B.low ambient temperature C.clogged ventilation ducts D.an open in the shunt field
