单项选择题
A.neutralize armature reaction
B.conduct electric current to an outside circuit
C.convert DC current to AC current
D.provide excitation to a DC generator
单项选择题 Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?（）
单项选择题 Since fuse elements are made of zinc or any alloy of tin and lead, the melting point of the fuse element must be （）.
单项选择题 The most common source of excitation for synchronous motors is a/an （）.