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)

 

[Johnuk]

must be a lefty coz my gf writes like that lol

 

[mechelec]

ABB contactor could be the problem. Come across a few lately that are noisy. Sometime they pull in and are ok other times noisy. Can you swap the contactor ?

 

[tazz]

Would suggest running the 12 relays on a tem 12v battery ......this will prove or eliminate my idea of ac interference

 

[Lucien Nunes]

Hmm. It's nearly new years, I've just spent 10 mins looking at that rat's nest and I'm not spending any more trying to make it out. I could read and memorise a dwg with 50 relays in the time it took to get an idea of what's going on there. But I think I can see problems.

1. Unless I'm mistaken, the genny power is fed backwards down the shed CU submain to the main CU.
2. The main contactors are not interlocked, therefore a small control relay failure could cause the sources to become paralleled.

There are other oddities but I'll leave it at that for now because those two, If I've read the 'dwg' correctly, are showstoppers. Correct me if I've got the wrong end of the stick. Also, BTW, how is the genny output referenced to earth?

 

[Knobhead]

Ten minutes Lucien?

One minute and I was going cross-eyed.

Bernard, to give advice we need legible information.
If the work is anything like the drawing I would suggest getting someone that knows what they are doing to look at the install for you.

 

[Bernard1991]

The circuit diagram is more for electronics wizz kids only originally posted this to find out how I can reduce the noise from the main abb b50 contactor I doubt it's anything to do with the electronics as the contactor is only run by a double pole relay which acts like a switch and the relay is 5a rated so there's plenty of leeway with current demand
and if any problems arise the system has plenty of warming lights and if the mains contactor gets stuck on then the generators start button will not activate the starter motor
And It shall be regularly maintained and may never be needed but good to be there just incase there's a power cut or black outs predicted in 2014/ 2015

 

[tazz]

Bernard, with all due respect to you...most of the guys commenting here are engineers involved in switch gear....and not your domestic sparks.....our jobs involve producing Schematic drawings for final approval, and if we were to submit hand sketches such as your drawing we would be all sacked. your sketch shows ultra low voltage, relays switching low voltage contactors, not electronic wizzardrey .......Now back to your problem. 1. do with have a stabilizer 12v dc supply, 2. are the contactors new..3. are the 12v relays polarized with a internal diode. Most of the guys here will help you, if you give them the information

 

[Engineer54]

The circuit diagram is more for electronics wizz kids only originally posted this to find out how I can reduce the noise from the main abb b50 contactor I doubt it's anything to do with the electronics as the contactor is only run by a double pole relay which acts like a switch and the relay is 5a rated so there's plenty of leeway with current demand
and if any problems arise the system has plenty of warming lights and if the mains contactor gets stuck on then the generators start button will not activate the starter motor
And It shall be regularly maintained and may never be needed but good to be there just incase there's a power cut or black outs predicted in 2014/ 2015

You can make all the electrical/electronic interlocks you like, at the very end of the day, it's going to be the mechanical interlock that saves YOU and the day!! Every manual or auto transfer switch /changeover switch i've ever seen in all the years i've been in this industry, have always had a physical or mechanical means of preventing paralleling of the 2 supplies.

 

[Lucien Nunes]

We have answered your question about usual causes of noise in AC contactors, i.e. failure to close completely and loose fasteners / core parts. We have also enquired into the background to your question, partly out of interest and partly out of caution. Controlling multiple sources of energy involves additional hazards that domestic sparks and DIYers are often unfamiliar with, therefore most home-built changeover schemes are flawed, some dangerously so.

I raised a couple of points of concern in a previous post because it seemed you had omitted to address some simple, fundamental requirements. I am now unsure as to whether you know yourself whether you have addressed them:

I could put in place a safety measure where if the main contactor ever sticks on the generator will not start up

if the mains contactor gets stuck on then the generators start button will not activate the starter motor

Scrappy drawings aside, I do not think you have a safe solution there nor the background knowledge of switchgear design needed to produce one. Please bear in mind that the maximum peak voltage present in your system could be in excess of 700V, that failure of the separation could endanger personnel working to restore the public supply, and that protective devices in your domestic installation may be defeated by an IT generator source. Echoing the above comments, I would suggest seeking expert advice and help with this project before putting it into service.

 

[Bernard1991]

I shall look into what I have put together and look into greater detail on all the comments and suggestions put to me and re-do areas that need doing
thanks for all the advice

 

[Bernard1991]

Had a quick scan through google and shall defiantly be getting a mechanical interlock and get annother abb b50, use that in the mains and the noisy one I'll blow out on the air line and use that for the generator side and have a abb mechanical interlock between them and change the 230v relay in the control unit for a 12v one and use a little led 12v dc transformer to run it when the generator is on line
thanks again for the advice on the interlock

 

[PEG]

Echoing a bit here,bernard,but the separation from public supply part cannot be under-estimated.The very situation where engineers could be at risk is WHEN your generator will be in action. Have seen this problem occur,supply down,geny stalling in and out,attempting to feed two other yards down the lane and failing. Imagine having a burst pipe in your kitchen,you turn off the stop cock and water comes under pressure from the other side of the burst.Hide the key to the generator under the DNO's main fuse...

 

[Darkwood]

Reflecting back to the original post Bernard you were only asking about a noisy contactor and now you hopefully are leaving a little better knowledged, weren't trying to belittle you in any way but needed to get across what you were attempting to do isn't as straight forward as making a functional control circuit ... that an easy thing to do but making one that is both in compliance and fail safe can mean the difference of thinking you know what your doing to actually been far from it and building a dangerous set-up this really isn't something you can just pick up of the tinterweb their are many standards to building this control system you will be required to meet which we haven't even touched upon.

I believe either way you are still going to build this panel but think its right for us to show our concerns and at least you know its not as straight forward as just making a functional unit.

 

[Knobhead]

Don't look in to it, act on it. When not if it goes wrong, you're neck is on the block.

 

[Bernard1991]

I am glad I posted on here otherwise I wouldn't have known about the interlock but I would have thought my wholesalers would have mentioned it when I told them what the second contactor was for as I told the guy what it was going in and he's meant to be a wizz with control gear
but have emailed abb if they do a interlock for the abb b50 and if any smaller amp rated contactors will fit that interlock
hopefully they have done a interlock for it as that mains contactor is the most expencive part looked it up new and it's anything north of £100 I got it off eBay £20-30 all that was wrong with it was the din rail locking tab was missing which I didn't need just slotted it onto a wylex din rail and put a self tapper through one of the mounting fixings oh and possibly it's humming that I'll take a look into next weekend

But once its it's all complete and fit for service I'll put a few pictures up of the whole completed system

 

[Lucien Nunes]

Don't forget to use an electrical interlock as well as a mechanical one. I.e N/C contact on mains contactor breaks coil circuit of gen contactor, N/C contact on gen contactor breaks coil circuit of mains contactor.

Some other factors to consider:
a) Relays welding with C, N/C and N/O all connected
b) Genny misfiring and producing low or surging output, causing AC relays / contactors to chatter in and out rapidly and arc heavily
c) Earth referencing of genny output
d) Peak voltages present when mains and genny both energised but passing through 180° out of phase
e) Transients on the mains causing contactor flashover between sources

Item b) caused carnage on a portable electronic system that had a UPS / transfer unit of my own making. The operator started the 2kW petrol generator and set up the equipment rack, then while she was busy away from the rack somebody stopped the genny without authorisation, moved it, restarted it but unknowingly put the choke on. The genny coughed and spluttered and produced a low and unsteady output well below 50Hz. My transfer switches reacted very quickly and kept flicking back and forth, shedding and restoring loads etc. Certain pieces of electronic kit in the rack didn't like this, so by the time she had gone to rescue the genny and taken the choke off, there were blown fuses, transistors, VDRs and a burnt-out transformer.

NB:

would have thought my wholesalers would have mentioned it when I told them what the second contactor was for as I told the guy what it was going in

You, and only you, are responsible for the design and execution, unless you formally commission someone else to do it. And no device is infallible, not even a mechanical interlock.

 

[Guest111]

TLC do a changeover switch for under 100 quid,anyone that can fire up a genny can surely operate one of these as well,and would be safer and less complicated than the OP,s idea,people go banging genny,s in without proper thought to the important issues concerned with safety,leaving aside earthing for a moment I,d be more concerned about the risk of electrocuting somebody working on the network if the genny backfeeds into it.
A friend of mine has a neighbour who rigged one up and was quite proud of the fact that in a power cut he thoughtfully provides power to the other cottages in the row,in other words he's backfeeding into the network.I tried to point out the error of his ways but he couldn't see the problem,I hope for his sake that the man in the cap and gown sees it from his point if and when it all goes wrong. Yes its nice to be able to have power in a power cut BUT not at the potential expense of others lives.As for the wholesaler not advising him about things he needs to remember that most of the people who work in them are not electricians,and it is up to you the buyer to ensure that whatever you buy is not only fit for the job you are using it for but that the work complies with any relevant regulations.

 

[Engineer54]

At the end of the day, there's a lot more to providing a standby generator supply to a domestic installation than first meets the eye. Most will without knowing, buy a generator that is wholly unsuitable for use with domestic appliances, which can in the right circumstances take out some very expensive equipment. Earthing arrangements of generators is another area where many get things wrong...

 

[Damian Petsas]

Why not change the set up so the house connector is normally closed therefore it won't be energised all the time, and the generator one normally open and change the relay wiring to suit. I agree with the previous posts you really should have a mechanical interlock.

 

[Bernard1991]

Well I will be changeing the contacotor set up found a abb Aline 60a contactor on eBay just waiting on abb to confirm a few details before I buy it
what I also will do is put up a new thread on what I have got so far with the changes I'll be making and try to explain how it works to the best of my ability and any opinion on the thread will be taken into consideration and be acted upon as this has got to be done so it's safe.
As for earthing I allways knew more would be needed than just the earth the generator supply's I was going to bond the metal frame to the c/u earth and come one here to ask if there was anything else that is needed in terms of correct earthing plus I allways knew the importance of separating the supply from the generator

thank you all for the information you have given me again it's been a big help

 

[Lucien Nunes]

Why not change the set up so the house connector is normally closed

Contactor? Because in the event of a control circuit fault it is more likely to fail to a dangerous condition. I would not like to rely on power being supplied all the time something needs to be isolated. If a DC coil were used, subject to specs it might be possible to reduce consumption with an economiser resistance bypassed by a N/C contact.