Loud buzzing motor contactor
- Thread starter JdoubleU
- Start date
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Tried cleaning the pole faces?
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Many times the Coil Laminations will cause the buzzing. Clean that area also
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If the contactor coil is designed for 240 and you are driving it with 208 it might not be pulling in fully and buzzing as a result.
And there should be shading coils on the pole(s) to hold the magnetic field through the zero current points of the cycle. If these are damaged, it can also cause buzzing.
Or are you just talking about the noise when it pulls in?
And there should be shading coils on the pole(s) to hold the magnetic field through the zero current points of the cycle. If these are damaged, it can also cause buzzing.
Or are you just talking about the noise when it pulls in?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Was it quieter and has BECOME noisy, or has it ALWAYS been noisy? Makes a difference.
The top five reasons for contactors becoming noisy:
Get the drift here?
Example of a broken shading coil:
The point is, anything that gets in between those steel mating surfaces and does not allow them to come completely together will make them buzz. Also, the shading coil / ring is a component of the design to SPECIFICALLY deal with the buzz caused by AC coil power, so if that breaks, even if the broken pieces fall all the way out, it buzzes.
If the voltage is below the drop-out threshold, the coil will (should) fully drop out or worse, chatter violently which results in a rapid burning or welding of the contacts, as in a matter of minutes. But it should not really make it begin to hum, so it's not likely that. Coils are supposed to function this way: all or nothing. When the chattering happens, it's because that coil current is too much for the supply (usually an undersized transformer), so when the coil pulls in, the voltage drops, it releases the coil, which removed the load, which allows the voltage to try to pull in the coil again, which causes a voltage drop, etc. etc. ad nauseum.
Now, the top 5 reasons why a contactor coil buzzes loudly from the outset and stays that way:
The top five reasons for contactors becoming noisy:
- Dirt buildup on the pole faces between the armature and core of the electromagnet. Not the contacts, the steel parts.
- Rust on the pole faces of the armature or core.
- Squashed bug carcasses on the pole faces of the armature or core.
- Pieces of wire insulation from stripping of wires getting caught in between the pole faces of the armature and core.
- Broken shading coils in the armature or core.
Get the drift here?
Example of a broken shading coil:
The point is, anything that gets in between those steel mating surfaces and does not allow them to come completely together will make them buzz. Also, the shading coil / ring is a component of the design to SPECIFICALLY deal with the buzz caused by AC coil power, so if that breaks, even if the broken pieces fall all the way out, it buzzes.
If the voltage is below the drop-out threshold, the coil will (should) fully drop out or worse, chatter violently which results in a rapid burning or welding of the contacts, as in a matter of minutes. But it should not really make it begin to hum, so it's not likely that. Coils are supposed to function this way: all or nothing. When the chattering happens, it's because that coil current is too much for the supply (usually an undersized transformer), so when the coil pulls in, the voltage drops, it releases the coil, which removed the load, which allows the voltage to try to pull in the coil again, which causes a voltage drop, etc. etc. ad nauseum.
Now, the top 5 reasons why a contactor coil buzzes loudly from the outset and stays that way:
- Cheap contactor
- Cheap contactor
- Cheap contactor
- Cheap contactor
- Cheap contactor
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
I am beginning to see a pattern here too.
Stop fretting.
Just replace the bladdy thing.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
So, what was the verdict?
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