Noisy contactor

[Bernard1991]

Hello I have installed a 100amp contactor in a generator control system I have designed tested and installed
its a simple basic design
two 230v ac contactors controlled individually by 12v 250v contact relays (12v relay used to get away with a cat5 between shed and house) and to change it all over a 230v coil Dp dt relay so when the generator is running the supply is disconnected and the house runs off the generator regardless wether the mains is live or not and disconnects when the generator is off to protect the generator

but the issue I'm having is the contactor on the mains side is humming or buzzing (how ever you would like to put it)
quickly got a app for an idea of how loud the noise is and got arround 30-40 db
the contactor is a abb b50 100a contactor it doesn't do much switching it's pretty much engaged all the time and when i press hard on the test button for dead testing the hum reduces, it's defiantly not arcing

is there a way I can reduce the noise?

Thanks bernie

 

[tazz]

Can you post a drawing or sketch, of the circuit you have designed / installed........can understand the lv coil buzzing but not the contacts

 

[itselectric]

Check the faces of the magnetic core which come together are clean, just a little bit of dirt can cause the contactor to buzz.
Also If the core has not been wound tight then you will get the plates vibrating, the only real answer is to replace in this case.

 

[Engineer54]

If you have designed and installed this changeover system yourself, i hope you have also mechanically interlocked the mains and generator contactors.

Many things can cause a contactor or relay to buzz, those that have been stated above, to being fixed on an uneven surface, strain being asserted, loose fixings ...and so on.

 

[Pete999]

Yep as itselectric said try cleaning the magnet faces first off

 

[Darkwood]

I would also like to see a wiring plan too out of interest to ensure you haven't set yourself up to a having the generator fly through the wall if if you have a mechanical failure like a jammed contactor... when you put the national grids almost unlimited power against the unsynchronised very limited genny supply.... you ever seen a motor stop instantly :shocked3:.

As for the noisy contactor ... many from coil voltage too low to dirt ingress as mentioned above.

 

[Lucien Nunes]

What they said, plus if you have a mechanical interlock check that it is positioned correctly and not preventing free movement of the contactors.

 

[Bernard1991]

I'll get a picture up soon lost the original drawing which resembled a snakes wedding being only a first draft and made improvements to it as I built it will also throw in pictures of the units
and I do see you concern dark wood I could put in place a safety measure where if the main contactor ever sticks on the generator will not start up when the start button is pressed on the control board

 

[guest119]

Could you not have done the same thing with a changeover switch, and aux terminals to start the genny?

Boydy

 

[Bernard1991]

Yeah my dad wanted a change over switch but the cost for one was daft and was big and bulky and would have had to run annother armoured cable to the shed so would have cost over£200 just for materials so far I spent half that and all my mother needs to do is start the generator and it'll change over automatically as my mother isn't electrically minded and don't fancy her calling me at work to tell her how to change it all over

 

[Bernard1991]

Here's the new circuit diagram it's incomplete but there's enough there to get a idea of how it's controlled everything has a illumination I.e neon for mains power, neon for genny power, led for mains contactor closed, led for genny contactor closed, led for internal transformer and a led for the back up relay for over night power if a prolonged power cut is in effect

 

[Darkwood]

I'll get a picture up soon lost the original drawing which resembled a snakes wedding being only a first draft and made improvements to it as I built it will also throw in pictures of the units
and I do see you concern dark wood I could put in place a safety measure where if the main contactor ever sticks on the generator will not start up when the start button is pressed on the control board

Putting a simple aux contact won't comply just to risk assessment as others have said you need a mechanical interlock as well as electrical isolation to coils if one fails the other is there for redundancy.. and the mechanical interlock is very reliable obviously routine inspections will back up any possible issues that arise.

 

[ian.settle1]

Could also be the laminations of the magnetic core buzzing.

 

[Darkwood]

No offense but you have no concept of how to draw wiring diagrams its over complicated almost impossible to follow and ive had the pleasure of using old Italian and Russian machine schematics without knowing the lingo and trying to establish old symbols so usually im good at deciphering this kind of stuff.

 

[Bernard1991]

I know the difference between a block, wiring and circuit diagram
I purposely put the circuit diagram up to show each component how there connected and how they work a wiring diagram wouldn't show any other information other than where to connect the cables to the components and to the printed circuit board connectors in my system
I can make a wiring diagram but it's not going to give anywhere near the information as my circuit diagram if that's Easyer for yourself

 

[Lucien Nunes]

I was going to look and see if I could find fault with the interlocking or isolation but you seem to have posted a pic of a bowl of noodles by mistake.

 

[tazz]

wow Had to save a expand the sketch......question what is suppyling the 12volt relays, a power supply or just a step down transformer...?

 

[Darkwood]

Ive printed it out and can't make out half the wording , its a chore trying to second guess what half of it is... yes the wiring plan would have been ok had your handwriting not been at the same level as my Doctor and had you at least found a straight edge to use. It might be ok on your table top but it hasn't transposed well onto the computer.

 

[Bernard1991]

There's two 12v supplies tazz
ones a battery for when there's no ac voltage going to the 12v led transformer (perfect for the low power required for the low volt side) and the change over relay that runs the system as without the 12v power you can start the generator but the system will not change over
then the other relay that swaps it all over its operated by voltage from the generator it's self, there for taking the 12v from the relay on the mains contactor and sending it to the relay on the generator contactor
thus closing the generator contactor and opening the mains contactor and vice versa when the generator is shut down

 

[tazz]

if your saying that one psu is an led transformer.....then i can only suggest there is ac on the 12v circuit, if its 12ac then then there is 50hz there....if half rectified...the is 100hz there....great potential for buzzing in a contactor 50-100 times per second (a buzzer)