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]

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

 

[Marvo]

Why are you repeating the post you made 15 mins ago which two of us responded to?

I could repeat the post I made 26mins ago and say 'I'm confused'......

 

[Knobhead]

You’re confused? I gave up ages ago.

 

[Darkwood]

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.

Exactly what are you testing between?

Control circuits are not as clear cut as you may think if say your coil is 400v and you had an issue with A1 supply then it will still show 230v both side of the coil to Earth.... Ensure you understand the nature of the control voltage and ensure this corresponds to the coil voltage.

This thread is going around in circles it seems and TBH if the simple task understanding the set-up and relevant voltages is getting you confused then your clear lack of experience in this area of electrics is making me think you are taking on jobs you are not competent to do and strongly suggest you get supervised experience for a few yrs before accepting any similar work.

It can be a simple set-up to buy a ready built start/stop contactor and fit it to a grinder for example but its more than just knowing the correct one to buy... if you are delving into the line of work then you need to have working experience and knowledge of machinery, controls, faulting and the BS60204.

The concepts of a burnt out contactor depend on what is meant by burnt out, what checks were made to find and/or isolate the cause, and whether the unit was spec'd correctly in the first place ... although we can make a few suggestions here we are lacking vital info and hence we are going around in circles.

-You need to be sure of the coil voltage.
-You need to be sure of your testing procedures and understand control voltages can have many back feed issues giving misleading info ... also if tranformed control voltages you need to know the TX output earthing arrangment to understand what results you get (Unlikely an issue if you have mains supplied L/N 230v or 400v).
-Ive been working 25yrs and the term fault batch is to blag the customer its very rare to get a replacement part that is faulty -if it suffers the same fate then you should be looking at others possible causes.

You won't rewire an house without understanding knowledge of the circuit theory and devices installed to protect them... hence a fault can be tested for and usually traced so why go into industrial and work on things you have no practical understanding of... please don't take this the wrong way but if you mess up no insurance will cover you for incorrectly designed / spec'd goods and the consequences can be extremely expensive.

 

[Deleted member 72666]

The panel has the push start on the front and the stop button also. The machine is formed of three parts that are switched by three start buttons that are in depended from each other. At first it was the overload that was not working so that was replaced and worked for around two weeks then the contactor coil went. The contactor was changed now the contactor has welded shut and coil burnt out. Any ideas what would cause this? All the connection are correct and it was working for two weeks before it went.

It could be that the supply for the control circuit is fed from one of the other machines (bad practice if no means of isolation and labelling) so check that, but what could have happened is that the control cct voltage is 400 volts and you have been given a contactor with the wrong coil voltage, I would pull one of the other contactors out of this panel and see what voltage is printed on the coil.
Whatever the outcome then please update this post, thanks.

EDIT: What is your location, if you're not too far away I may be able to help.

 

[netblindpaul]

So is it a combination machine, spindle moulder, saw & planer/thicknesser?

It has 3 motors, though?

IF this control was fitted or the machine built after 1998, then to comply with regulations, if, it is as I describe here then it MUST have a control transformer, and must not use 400V control, or 230V Ph & N for control.

 

[Darkwood]

400v and 230v L/N is still acceptable as a control voltage but only under certain set-ups hence why you can buy and fit a all in one start/stop contactor, O/L + enclosure with 400v coil or 230v-agree NBP most control systems are now subject to this regulation regarding control voltages as most will be exporting the voltage for remote control, limit switches etc...but its not MUST in all set-ups.

BS 60204 - 1 (9.1.1)

Exit clause states 'Transformers are not mandatory for machines with a single motor starter and/or a maximum of two control devices (for example interlock device, start/stop control station)

 

[netblindpaul]

Yes a stand alone starter is OK, but, this is a 3 motor machine with 3 work stations, if, it is as I understand it, thus it must have satellite controls from the main starter.
Plus it has not got a single motor starter, it has 3!
I have never said it is a must in all circumstances, but on a combination machine you'd have a job justifying not having a control Tx.

 

[netblindpaul]

Oh, plus if you go back before 1998, then the requirement for control Tx's was there then, and back as far as 95/93 and IMHO it was stronger then than it is now.
I only used 1998 as the break point due to PUWER which drew a line in the sand so to speak.

 

[Darkwood]

I know what you meant paul ... just elaborating your post is aimed at the OP's circumstances and the capitalised use of the word MUST should not be interpreted for all set-ups as may be read by others without experience in this area... wasn't knocking your post just adding to it.