why do line voltage AC power relays buzz

Thread Starter

sdowney717

Joined Jul 18, 2012
706
I have one and when new never buzzed. But lately it can be a buzzing quite a bit. It will buzz when the circuit goes under load, and the voltage supply to the relay falls and my improve a little as the load keeps running. Or it may just buzz all the time, seems very random. The buzzing noise intensity varies tremendously, from obnoxiously loud to almost silent.
So can it be cleaned, greased? Is where the arm comes down onto the coil rusty or dirty? It might, if I whack at it, stop buzzing.
 

MaxHeadRoom

Joined Jul 18, 2013
26,002
Usually two reasons, poor mating surface of the armature, low coil voltage.
Answer: Use DC coil relay!;)
Edit: Plus small bridge.
Max.
 
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Thread Starter

sdowney717

Joined Jul 18, 2012
706
I did convert 2 AC powered coil relays to DC volts, I used a walwart and a resistor voltage divider. It takes about 16-17vdc to operate a 120vac coil, and now they never buzz. But doing that wastes a little bit of power. I suppose when I get time, I can take the relay off and examine it. Maybe if I cleaned and put some grease on the mating surface.
 

MaxHeadRoom

Joined Jul 18, 2013
26,002
You don't need any power supply when switching to DC with line voltage, just use a DC line voltage coil (120dc/240dc) and a small bridge rectifier.
Clean the mating surfaces and making sure there is nothing stopping the armature from closing completely.
Max.
 

Thread Starter

sdowney717

Joined Jul 18, 2012
706
You don't need any power supply when switching to DC with line voltage, just use a DC line voltage coil (120dc/240dc) and a small bridge rectifier.
Clean the mating surfaces and making sure there is nothing stopping the armature from closing completely.
Max.
Got to buy a new relay to do that. Otherwise you make do with something cobbled together.
It has been maybe 5 years on my relay mod so far and working still. The relay I modded can be expensive, it is a 4 pole DT 30 amp power relay.
They do come in DC12, 24, and AC 120/240vac coils, etc....
https://www.gamut.com/c/electrical/...VjKH6rZGMxMYgEDbYuPCG1sR2QfFUMCwaAu58EALw_wcB
 
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