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 （）.
单项选择题 Time delayed or delayed action-type fuses are designed to （）.
单项选择题 Which of the following statements is true concerning all three-phase alternators?（）
