单相异步电动机按原设计配绕组时,铁心利用率( )。若要改变极数其利用率会降低,性能也会变差。
A. 最低
B. 最高
C. 略下降
D. 略上升
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Nobody but Jack and Smith ______ in the office yesterday.
A) had been
B) was
C) were
D) is
______we all know, Mr. Wang is a very warm-hearted person.
A) Which
B) That
C) As
D) It
GND—30型高压线圈匝问耐压测试仪是对高压电动机线圈匝间绝缘进行耐压检测的专用仪器。同时可灵敏地检测出线圈的( )。
A. 介质损耗
B. 导线电抗
C. 绝缘水平
D. 匝间故障
半精车对电机转轴需要磨削加工的( )挡留有一定的磨削余量。
A. 端盖
B. 轴伸
C. 定子
D. 转子