Motor Design

  • Thread starter Bob Dannenfelser
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Thread Starter

Bob Dannenfelser

Can anyone tell me which of the following types of motors is designed for use in correcting power factor: Polyphase, Wound Rotor, Induction, or Synchronous? It's an exam question that I cannot find an answer anywhere else!
Bob Dannenfelser

Niall Watson

From distant memory...
Synchronous motors can be used to correct inductive power factors.
Certain (older) power stations use synchronous motors on cooling water
systems (i.e. very large motors) to correct the overall PF of the power

PES Automation Ltd.

Niall Watson

Phone: 01283 741333 Fax: 01283 562303

Colin Walker

Wound rotor, (synchronous) motors are often used to balance a plants power factor. Varying the rotor excitation changes the power factor from lagging to leading. This is very effective because the are generally the largest motors on a site and can therefore counter all the lagging VArs produced by the smaller induction motors.
Regards Colin

John F. Vales

Synchronous Motors are used to correct power factor. In fact, they run for free, using the power difference. They're often used in bigger automotive plants.


John F. Vales
Director of Technology
Wes-Tech Automation Systems, Inc.
[email protected]

Vitor Finkel

1) A synchronous motor, when over-excited produces out-of-phase currents, similar to capacitors, and so is used to help to correct the power factor.

2) Don't you feel like you are cheating ?

Trevor Ousey


From memory, a Synchronous motor is used for power factor correcting. The details I remember is that it was generally? oversized, sometimes it would be run without a load or lightly loaded. I was thinking of digging out my old electrical
principles text book, but..... If you need some more details, I could try and find it. Let me know.

Trevor Ousey
[email protected]
A wound motor, when break, wired as transformer, input on stator/ output on rotor can adjust power factor to 1 if its rotor is set at the exact power factor angle in respect to stator position. It is the best of all existing methods.

David Heagerty

Bob, The synchronous motor is most widely used for correcting power factor. With the addition of the rotor Excitation field, plants can easily control the current through the field windings to change the phase relationship between current and voltage.

harsh ramaiya

syncronous motor can be used to correct power factor. syncronous motor can work on wide range of power factor, from unity leading to unity lagging , by changing its excitation. in this way by connecting the syn motor in parallel with the load power factor of the load is improved. the motor relieves the line form heavy MVAR. a syn motor operating in the above explained way is called as synchronous condenser.