For a 2-pole, 50Hz 3-phase induction motor, is the nominal slip sN=0.04,then the nominal rotating speed is ( ).
A. 3000 r/min
B. 1000 r/min
C. 2880 r/min
D. 1440 r/min
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The nominal power factor of a 3-phase induction motor is 0.85, then the power factor under light load condition can be ( ).
A. 0.9
B. 0.87
C. 0.85
D. 0.5
The nominal voltage UN and nominal current IN on the nameplate of a 3-phase asynchronous motor refers to ( ) respectively.
A. line voltage/phase current
B. phase voltage/line current
C. line voltage/ line current
D. phase voltage/ phase current
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
( ) are rotor parts of DC machines. ①main magnet poles②commutating poles③brushes④bedplate⑤armature iron core⑥commutator⑦armature windings
A. ①②③④
B. ⑤⑥⑦
C. ③④⑤⑥
D. ②③④⑤