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Eliminate 60 Hz hum on contactor with 120V coil

Discussion in 'Power Electronics' started by aaronk, Sep 14, 2021.

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  1. aaronk

    aaronk

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    0
    Sep 14, 2021
    So I am using a contactor in an enclosure to switch a load, using 120V (AC) that is coming from an older stereo receiver. When turning on the receiver, power gets sent to the contactor, it engages the coil and switches on the load. The load? A bunch of lava lamps, holiday lights, and other fun things in my man-cave garage.

    Problem is, there's a 60 Hz hum it makes. Sometimes it's loud, sometimes medium, sometimes quiet. Turning it off and on will often change it from one to another. I want quiet always. Is there an easy solution for this?
     
  2. Bluejets

    Bluejets

    4,991
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    Oct 5, 2014
    If this is the buzzing from the contactor then it is the internal armature pole faces that are either dirty or faulty.
    Could also be low voltage...what is the source current capability.
    Can you show a circuit..??
    If just dirty, usually a wack will quieten them down temporarily.
    Perhas a spray with crc once cleaned.
    This is assuming it is able to be dismantled.
     
  3. Minder

    Minder

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    Apr 24, 2015
    One reason I always use DC contactor coils, also DC is much more efficient, i.e. less heat.
     
  4. aaronk

    aaronk

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    0
    Sep 14, 2021
    Well, it's a brand new contactor. Could it really be dirty? Maybe it needs to be "broken in"?

    Yeah it would be nice to use low-voltage DC instead. Unfortunately I only have AC to control it. I guess contactors, at least the ones that are switched with 120 VAC, are not necessarily rated for quiet environments.

    I was hoping there was an electronic solution for this... a filter or something.
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    Armature pole faces can still be rusty or dirty, depends how long it has been sitting, where you bought the contactor etc etc.
    Probably is a solution...you didn't answer my other possibilities nor provide a circuit of what you have.
    Go back and read the rest of my reply #2

    Found an example video ...start around 3:30 mark

     
    Last edited: Sep 16, 2021
  6. Minder

    Minder

    3,103
    664
    Apr 24, 2015
    Have you checked this source of 120v for actual voltage?
    An AC contactor coil does not tolerate much in the way of reduced voltage.
     
  7. Bluejets

    Bluejets

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    Oct 5, 2014
    I asked for that among other things but no reply on those queries.
    The part about it coming from an old stereo raised my suspicions.
     
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