单项选择题
When current and voltage reach maximum values at the same time, the power factor is（）
A.minimum
B.maximum
C.leading
D.lagging
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相关考题
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单项选择题
Which is an acceptable means of correcting high mica between commutator bars?（）
A.undercutting
B.sanding
C.burnishing
D.filing -
单项选择题
Generator brushes are staggered to（）
A.reduce current pulsations
B.reduce brush chatter
C.prevent uneven commutator wear
D.allow greater power generation -
单项选择题
The voltage output of an AC generator is controlled by（）
A.varying the DC exciter voltage
B.varying the reluctance of the air gap
C.regulating the speed of the prime mover
D.shorting out part of the armature windings
