MSW inverter silence hum buzzing relay sound?

Discussion in 'General Electronics Chat' started by sdowney717, Nov 1, 2012.

  1. sdowney717

    Thread Starter Member

    Jul 18, 2012
    385
    13
    These relays are new.
    PM17AY-120 4 pole, 120vac coil and are like these here
    http://www.alliedelec.com/search/productdetail.aspx?sku=70213398

    I bought two relays but not from that site, I got them off ebay.
    I created a power transfer box to switch from 3 power sources Inverter-generator-grid power. The relay have 4 poles and I switch twin 30 amp power in a boat.

    I notice that when relay coil for inverter is on, it has a more noticeable hum-buzz type sound. I assume due to being a MSW wave.
    So was wondering if that could be improved?

    picture of roughed out box showing relays. I welded that box up using an old fuse box from the 1960's.
    [​IMG]
    simplified schematic idea
    [​IMG]

    [​IMG]

    [​IMG]
     
  2. sdowney717

    Thread Starter Member

    Jul 18, 2012
    385
    13
  3. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,220
    AC relays can have a hum or buzz when energized. To minimize it you could insulate the box.

    If the buzz is from the inverter, then that is likely due to the change in load current when the relay is energized.

    Noted in your picture that one of the white wires on the bottom right is loose.
     
  4. sdowney717

    Thread Starter Member

    Jul 18, 2012
    385
    13
    I fixed it.:)
    I loosened the spring tension by bending the spring arm attachment point.
    This took tension off the relay arm. Now it no longer buzzes. Being at a marina, the power is not very good, so slight brownouts when you turn on heavy loads. I noticed the grid relay started buzzing every time the microwave oven turned on.
    It still opens fine even with less spring tension.

    The picture is just a rough in.
     
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