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

 

[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.