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What type of switch is this and how does it work?

Discussion in 'General Electronics Discussion' started by BillGunn, Aug 17, 2016.

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  1. BillGunn

    BillGunn

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    Aug 16, 2016
    [​IMG]

    It is a 3 speed variable switch with 3 prongs with wires that lead to a copper coil. It goes to a vintage fan.

    First, how do these work? What is the function of the coil? It looks like an ignition, or induction, coil off of a small engine. Does it serve a similar purpose?

    Two, would it be possible to find replacements? It is quite worn. Seeing as this is from the 1950's, would they still make identical products?

    NOTE: I was essentially called out for even thinking of working on this. Apparently no caution is ever enough. Thus, I will not touch it, or mess with it. I figured, if I made this thread about individual components that make up the whole, I could begin to understand (and, you know, learn) about this stuff.
     
  2. Minder

    Minder

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    Apr 24, 2015
    Could be a type of relay that switches the different rpm coil in.
    M.
     
  3. BobK

    BobK

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    Jan 5, 2010
    I suspect it is switching no inductance (for high speed) and two different inductances for lower speeds in series with the motor. These days, capacitors are usually used for this purpose, but inductors should work just as well.

    Can you trace the wiring and draw a diagram, include the power in and the motor?

    Bob
     
  4. duke37

    duke37

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    Jan 9, 2011
    Is that another coil at the top of the picture? If so,I agree with Bob.
    There does not seem to be any moving armature for a relay.
    The wire is fairly thick and it should be possible to rewind if necessary.With a shorted turn the fan will still work with an increased speed.
     
  5. BillGunn

    BillGunn

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    Aug 16, 2016
    [​IMG]

    I'm not an expert, and this is the best I could do.
     
  6. BillGunn

    BillGunn

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    Aug 16, 2016

    The fan functions fine. All works. I was advised though not to mess with it (due to my inexperience), as when turned on there is a current that travels through the metal frame of the fan that a non- contact voltage detector picks up, and I cannot trace exactly where this current could be originating from.

    {EDITED FOR CLARITY}
     
  7. duke37

    duke37

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    Jan 9, 2011
    In the UK we have PAT testing. All exposed metal parts must be connected to the earth wire and capable of carrying enough current to blow the fuse which should be as low a value as possible.
    It should be fed with an earth leakage breaker in circuit.

    You should test that there is no connection between the power circuit and the earth connection using a high voltage tester (Megger).

    You may get high voltage on the frame due to capacitance from a live wire. A decent earth connection should stop this.
     
  8. Minder

    Minder

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    Apr 24, 2015
    Appears to be a coil used as an auto-transformer mode.
    M.
     
  9. Bluejets

    Bluejets

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    Oct 5, 2014
    It's a standard run-of- the- mill 2 speed choke. As Bob said, high speed bypass, other two speeds provided from voltage drop in the choke. This type no longer used (again as Bob quoted.)
     
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