contactor burning out

[mcm]

I recently fitted a new contactor three phase 10amp with 230volt coil, now it was working fine for about two weeks and now seems to have burnt out. I can not manually push the contactor in even using a screwdriver as it is solid. The overload is set to 4 amps so shouldn't be a problem with that has anyone have any ideas why it has burnt out? I have heard it could be caused by a drop in voltage on a phase but what would cause this as it all tested out at 230volt before it went wrong.

 

[mcm]

Could be a bad batch but I would still check stop circuit for intermittent high resistance that would cause under voltage and maybe chattering of the contactor. Speak to Cromptons to see if there's been a problem (doubt they'll own up) and see if they'll replace it foc!

I have got the wholesaler to order a new one at no extra cost to me but don't want it to happen again as it would be hard to get a replacement if it happened again. I will look at the stop circuit also thanks

 

[Deleted member 72666]

A good tip when checking n/c contacts (or made n/o for that matter) is to gently 'tap' the item you're checking with the handle of your screwdriver as if to mimic vibrations that could be transmitted during operation and note any resistance variations, there should be very little if any for good contacts.

 

[Darkwood]

The coil voltage is 230v and I have checked this.

Yes ok but is the control circuit 230 or 400v .. undervoltage can still operate a contactor but not give a good contact hence i asked if the control voltage is the same?

 

[netblindpaul]

If it has 3 contactors in the enclosure, is it a new Crompton Controls unit, or an old Brook Crompton unit?
3 contactors suggests to me, star delta, or a d.c. braking unit possibly?
Are any of them mechanically interlocked?

 

[mcm]

If it has 3 contactors in the enclosure, is it a new Crompton Controls unit, or an old Brook Crompton unit?
3 contactors suggests to me, star delta, or a d.c. braking unit possibly?
Are any of them mechanically interlocked?

The unit is a new one, I will check if they are interlocked when I return but I don't think they are.

 

[Deleted member 72666]

Does the 230 volts come from a transformer or is the machine supply 3ph & N?

 

[PEG]

Bingo,i was just thinking where that coil obtains its feed from,as a lot of older woodworking tackle was 3PH only. Is that the only 240v requirement,and is it reliable...

 

[mcm]

Bingo,i was just thinking where that coil obtains its feed from,as a lot of older woodworking tackle was 3PH only. Is that the only 240v requirement,and is it reliable...

Yes it's 3phase and 230volt control circuit with no neutral. I have checked the stop start circuit and it's all reading 230volts that go onto the coil.

 

[mcm]

Does the 230 volts come from a transformer or is the machine supply 3ph & N?

No the supply is 230volt to control circuit with 3phase no neutral machine supply

 

[netblindpaul]

How is that?

 

[Marvo]

??? I'm confused.

 

[mcm]

Thinking about it if the coil is 230volt that is what they supplied, wouldn't it need to be 400volt if no neutral is present? All the control circuit is 230volt

 

[netblindpaul]

IF you have no N, & no control Tx, then your control V CAN NOT be 230V.

 

[Marvo]

Yeah, something's not making sense. Either it's 3-phase with no neutral and the controls would all be 400v or it's single phase and neutral in which case the motor and the controls would be 230v or it's 3-phase with neutral in which case the motor could be 400v and the controls could be 230v unless there's a TX.

As I suggested in post #21 some photos would help.

 

[netblindpaul]

IF we had the Crompton part code for the unit then I could tell you what was what.

We have a direct account with Crompton, and have done Warranty work for them on their behalf, so we know their current product incarnations very well.