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Homework Help: AC induction motor start

  1. Jan 31, 2010 #1
    Hello to all,

    I'm a student of electrical engineering. We have learned the basics about AC induction motors and we learned that single phase motor cannot start by itself. There must be some additional part that will produce phase lead or lag in order to create rotational magnetic field. That is clear to me. Furthermore we have learned that these AC motors have either run winding or run capacitor that is disconnected later via centrifugal switch. However, I wonder how this is done in everyday home induction motors like hair dryers kitchen mixers and similar? I don't believe they have centrifugal switch built in somewhere.
    Can you give me example how single phase AC motors start in home applications?

    My best guess is that these motors have run windings permanent built in and there is no anything like centrifugal switch. I thought that capacitor is used for this purpose since I have found one when disassembling a hair dryer, but my friend told me that this capacitor is not for start but for preventing EMC interference with other devices like TV. He told me that this capacitor faild and that he short circuited it and motor worked without any problems.

    Can you clarify these things for me?

    Thank you
  2. jcsd
  3. Jan 31, 2010 #2


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    These type of motors are called http://en.wikipedia.org/wiki/Shaded-pole_motor" [Broken].
    Last edited by a moderator: May 4, 2017
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