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

 

[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