单项选择题
The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains （）.
A.a magnetic operating coil
B.normally open line contacts
C.thermal-overload protection
D.a momentary-contact start button
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相关考题
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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 -
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 -
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
