题目内容

For a Δ connection 3-phase induction motor, we connect it in Y connection when it is running under no-load condition, but with same power source, then ( ).

A. the motor will stop because under voltage
B. same speed as Δ connection
C. the motor will running at a higher rotating speed
D. the motor will running at a lower rotating speed

查看答案

搜索结果不匹配？点我反馈

更多问题

( ) are rotor parts of DC machines. ①main magnet poles②commutating poles③brushes④bedplate⑤armature iron core⑥commutator⑦armature windings

A. ①②③④
B. ⑤⑥⑦
C. ③④⑤⑥
D. ②③④⑤

For a real transformer, the norminal voltage of primary windings is 440V. When the primary windings is connected to 440V power source, the open-circuit voltage of secondary windings is 110V, and the voltage decrease to 105V as the load current increase to nominal value. So the turns ratio of the transformer is ( ).

A. 4
B. 4.19
C. 0.25
D. 0.24

For a step-up transformer, the relationship between primary winding N1 and secondary winding N2 is ( ).

A. N2>N1
B. N2=N1
C. N2
D. denpends on its model

When the AC magnetic contactor is energized, for the flux before and after the moving part is attracted, ( ).

A. F(before)>F(after)
B. F(before)=F(after)
C. F(befoer)