Understanding Electrical Machines: Queries & Answers

[installer2001]

Hello Guys,
I am a beginner in the field of Electrical well i have certain queries to ask from u genius guys

1):WHY THERE IS NO BACK EMF in 3-phase INDUCTION MOTOR
2):WHY WE REMOVE RHEOSTAT after 3-5 seconds of STATRTING OF 3-pahse INDUCTION MOTOR.
3):IF WE APPLY SINGLE PHASE ,THEN HOW SINGLE PHASE ROTATE WHEN THERE IS NO MAGNETIC FIELD IS PRESENT
4);IF DC applied ON STATOR OF 3-phase INDUCTION MOTOR WHAT IS EFFECT ON TORQUE COMPONENT



PLz do reply bcoz i am very keen of acquiring knowledge regarding electrical machines
Thz in Advance

 

[Averagesupernova]

Hello Guys,
I am a beginner in the field of Electrical well i have certain queries to ask from u genius guys

1):WHY THERE IS NO BACK EMF in 3-phase INDUCTION MOTOR

There is.

2):WHY WE REMOVE RHEOSTAT after 3-5 seconds of STATRTING OF 3-pahse INDUCTION MOTOR.

There is no requirement that there is a rheostat to start with. I suspect you are referring to some sort of soft-start setup where starting torque is not important.

3):IF WE APPLY SINGLE PHASE ,THEN HOW SINGLE PHASE ROTATE WHEN THERE IS NO MAGNETIC FIELD IS PRESENT

It can't start that way, but it can run that way. It 'appears' that there is a rotating magnetic field.

4);IF DC applied ON STATOR OF 3-phase INDUCTION MOTOR WHAT IS EFFECT ON TORQUE COMPONENT

DC on the stator will cause the heating in the rotor. I would imagine torque would be reduced.