单项选择题
A.a magnetic operating coil B.normally open line contacts C.thermal-overload protection D.a momentary-contact start button
What will be the phase angle relationship of a six-pole...
单项选择题What will be the phase angle relationship of a six-pole, three-phase, rotating field generator （）.
A.60 B.120 C.180 D.360
The part of a fuse that melts and opens the circuit is ...
单项选择题The part of a fuse that melts and opens the circuit is made of （）.
A.copper and antimony B.steel and babbitt C.aluminum or beryllium alloy D.zinc or an alloy of tin and lead
Time delayed or delayed action-type fuses are designed ...
单项选择题Time delayed or delayed action-type fuses are designed to （）.
A.prevent grounds in branch circuits B.prevent opens in motor circuits C.permit momentary overloads without melting D.guard lighting and electronic circuits
