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Eliminate 60 Hz hum on contactor with 120V coil

aaronk

Sep 14, 2021
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Sep 14, 2021
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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?
 

Bluejets

Oct 5, 2014
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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.
 

Minder

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

aaronk

Sep 14, 2021
2
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Sep 14, 2021
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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.

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

One reason I always use DC contactor coils, also DC is much more efficient, i.e. less heat.

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.
 

Bluejets

Oct 5, 2014
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I was hoping there was an electronic solution for this... a filter or something.
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:

Minder

Apr 24, 2015
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, using 120V (AC) that is coming from an older stereo receiver.

Have you checked this source of 120v for actual voltage?
An AC contactor coil does not tolerate much in the way of reduced voltage.
 

Bluejets

Oct 5, 2014
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Have you checked this source of 120v for actual voltage?
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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