Testing a contactor/Awelco blowing trip

[Hitch]

Ive volunteered to have a Frank at me mates MIG welder, Awelco, identicle to my home machine as it happens. Mines currently staying with others at the moment so nothing to compare

It blows the trip everytime you try and pull the trigger, regardless of settings.
Removed covers, and found a wire (solid copper) goes from the contactor to the transformer, at the contactor end, a bit of insulation appears to have melted, and also a bit on the contactor. Also 'smells elecrical'

To test said contactor, i gather L1/2/3 and T1/2/3 should not have continuity normally, but when pressed in (energised) they do...? Have i read that right....?

 

[brightspark]

corect open circuit till energised . t 2 is having a burnout due to loose cable. slacken screw off clean the contact aeria . cut back cable and reconect . it might have damaged the contacts inside though

 

[Hitch]

Do they come apart, looks as if it would, or is it one of them things thats best not to!

 

[Paul.]

Thats a 3 phase contactor, it looks as if your only using 2 sets of contacts, you could move the burned cables over to t3, and the feed of course from L2 to L3

 

[Hitch]

Good idea Paul.

Just multimetered it, Seems as it should, no connections between L/T untill the switch is pushed in. And no connection between 1/2/3 pushed in or out.

Any other ideas...cant see anything obviously burned...i will have to get some pics of the insides. And have a more thourough check on the rest of the cables.

 

[Paul.]

You could take the cables out of T1 and T2, then see if it blows the trip, if not then the problem is after the contactor, if it still trips the problems before it, then work your way back through the circuit. does the contactor pull in under power when you press the trigger or does it trip before you get that far. A1 and A2 are the coil circuit.

 

[Hitch]

Cheers, i will put it back in and see what happens, i think he said the contactor goes in, then the trip goes imediatley.

Have a look myself when i have moment.

Get a few pics of the workings also. (or not as the case may be!)

 

[Paul.]

Next thing in the circuit after the Contactor will likely be the transformer, so it could be terminal or at least expensive.

 

[the snooper]

welding rectifier gone ?

 

[Hitch]

Noticed a slightly dodgy bit on the PCB earlier, looks like the copper had slightly melted. Just soldered a jumper between the 2 nearest linked points. Now when i short out the terminals on the euro socket, the contactor goes in and out, and wire motor runs round...
Just need a torch and some wire now to check it out!

Moved the contactor connections too the spare one also.

 

[Hitch]

Eventually got 5 mins to put it back togrther, loaded wire and put a torch on. Did a few tacks, and a few short runs, seems to be fine.

No parts required, bar a bit of wire a few inces long and a couple blobs of solder

 

[the snooper]

if you have to have a fault those are the ones to have .