Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Poles of AC Induction Motors

  1. Jul 25, 2015 #1

    I want to know determining the number of poles by inspecting coils inside the motor. Generally, there are formulas allowing us to plug a frequency, an rpm, and give off the number of poles, or we can just simply look at its nameplate.

    My reason for needing the inspecting is that my brother fixes burnt AC induction motors. As it was burnt by overloading or whatsoever already, he can not find the number of poles by operating it. Luckily, there are nameplates.

    One vulnerable point is in the case that a customer brings his/her burnt motor with a burnt nameplate.(The windings are burnt, but it still can be observed its winding physical details like in the attached file) In this case,"How could I determine the number of poles by tracking stator coil connections?"

    I try to google this many times but what I've found are using the formulas mentioned above and looking at the nameplate. Also, what I've found is that a 4 poles induction motor does not always have 4 coils in one phase but it has to take care of how coils are connected ,and the site does not tell any further.

    the site:
    Thank you

    Attached Files:

    Last edited: Jul 25, 2015
  2. jcsd
  3. Jul 25, 2015 #2


    User Avatar
    Gold Member

    To a degree, re-winding a burnt up motor is a bit like building a new motor. You need to ask what speed is required for the re-built motor along with line frequency. Then figure the required number of poles from there.
  4. Jul 26, 2015 #3
    Suppose that I've got a required frequency and speed giving number of poles by using formulas. For examples, I've got 4 poles in one phase. Will there be only 4 coils in one phase producing 4 poles? (What I've learned from another site is that we have to take those coils' connection into account, but it didn't tell anything further, so I am not confident to trust it)
    Last edited: Jul 26, 2015
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook