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Why does changing two leads change the rotation of a 3 phase motor

Why does changing two leads change the rotation of a 3 phase motor

Why does changing two leads change the rotation of a 3 phase motor

(OP)
Why does switching two leads on a 3 phase motor change the rotation?    

RE: Why does changing two leads change the rotation of a 3 phase motor

Because each lead is 120 degrees out of phase, you create a rotating magnetic field in the motor.  Swap two leads and the field rotates in the other direction.  That's why certain single phase motors require start capacitors to "simulate" another phase.

RE: Why does changing two leads change the rotation of a 3 phase motor

It reverses the phase sequence resulting in sequence of rotational forces applied.  A<B<C changes to A<C<B, for example. The source sequence remains unchanged.

You may understand it better if you draw a wheel and note three points on its circumference 120 deg apart. Name them A, B and C.  Imagine it being rotated by three forces A to B, B to C and C to A.  If you interchange any two points of application, you will see the direction of wheel's rotation will reverse.

Rafiq Bulsara
http://www.srengineersct.com

RE: Why does changing two leads change the rotation of a 3 phase motor

(OP)
Thanks fellas. I'm sitting in a vfd siminar and the instructor couldn't answer.    

RE: Why does changing two leads change the rotation of a 3 phase motor

...resulting in reversal of...

Rafiq Bulsara
http://www.srengineersct.com

RE: Why does changing two leads change the rotation of a 3 phase motor

Sad that  "VFD seminar" instructor can't answer that question...


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RE: Why does changing two leads change the rotation of a 3 phase motor

(OP)
He couldn't answer anything. Very bad instructor and waste of money

RE: Why does changing two leads change the rotation of a 3 phase motor

(OP)
He couldn't answer anything. Very bad instructor and waste of money

RE: Why does changing two leads change the rotation of a 3 phase motor

He probably sells a lot of VFDs to people to whom that question would never occur.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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