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Machine Induction forge failure

Machine
PaulL

PaulL

Technologist at Large
Premium Member
It was all just going too well. And now, just as we're entering "thou shalt not use solid fuel" season, my little induction unit failed.
When I press the pedal it tries a few times to dump some power into the coil and then buzzes out an "over current" error that doesn't go away until I power cycle it. I can turn the power way down and have it put 100amps into the work for a few seconds, then the same thing happens.
Chiller has been keeping up, though the heating coil is the warmest I've ever felt it.
So my suspicion is that I have short somewhere in the induction coil, which would be no surprise to anyone who remembers the sorry shape this machine was in when the shippers delivered it.
Not looking foward to the surgery. I'd just order one of the US Solid ones at this point, except that I'm still not buying from that side of the border. Grumble.
 
PaulL said:
It was all just going too well. And now, just as we're entering "thou shalt not use solid fuel" season, my little induction unit failed.
When I press the pedal it tries a few times to dump some power into the coil and then buzzes out an "over current" error that doesn't go away until I power cycle it. I can turn the power way down and have it put 100amps into the work for a few seconds, then the same thing happens.
Chiller has been keeping up, though the heating coil is the warmest I've ever felt it.
So my suspicion is that I have short somewhere in the induction coil, which would be no surprise to anyone who remembers the sorry shape this machine was in when the shippers delivered it.
Not looking foward to the surgery. I'd just order one of the US Solid ones at this point, except that I'm still not buying from that side of the border. Grumble.
Click to expand...
Good on you Paul, you can fix it anyway.
 
Well, here's a smoking gun. Those two yellow wires had their insulation fused together and some burn marks at one end of the fused section. Here they are teased apart:
1751321219234.png

These are absolutely part of the current measurement system, coming right off that double coil threaded on the main power heading to the induction coil and going to the power PCB:
1751321299612.png

They are two of the yellow wires coming through the hole and in the bottom of the two rightmost connectors.

I separated them and tested the machine in place, and yes, it runs "fine" now. The real question is: should these sensor wires be getting that hot? I'm pushing the machine fairly hard with some forge welding, but I don't imagine sensor wires should be getting charred-hot, even in that circumstance.

Thoughts?

Paul
 
The insulation doesn't look burnt or deformed from overheating. Maybe there was a bit of pressure forcing the wires together and vibration rubbed them raw. I think I'd replace the wires or at least re-insulate and keep them separated with a small piece of plastic or wood taped in between them.
 
YotaBota said:
The insulation doesn't look burnt or deformed from overheating. Maybe there was a bit of pressure forcing the wires together and vibration rubbed them raw. I think I'd replace the wires or at least re-insulate and keep them separated with a small piece of plastic or wood taped in between them.
Click to expand...
I wound up wrapping them in electrical tape and using that to separate them and put them back to work. I'll see how it holds up!
 
You can separate wires with Ty wraps. Lightly run a tywrap around the two wires then run one around the first tywrap between the wires. I’ve even done this with ignition wires it works as a continuous separation in the wire run. Do it every so many inches to maintain the distance. It’s interesting those two wires burnt together is it possible they got something hot on them?
 
djberta said:
It’s interesting those two wires burnt together is it possible they got something hot on them?
Click to expand...
I don't see anything there - they just run loosely inside the case. They may have been damaged during the shipping mess and it took a while of heavy use for the problem to surface.
I'm going to run it for a while and then inspect the wires closely and see if anything is happening.
 
@PaulL - Wire amperage ratings usually depend on open air circulation. If you trap them inside a conduit or tape or any insulation, their current handling has to be derated. Even two wires held together reduces their ability to disappate heat usually by about 20%. They produce heat based on the current and the wire resistance. The fundamental problem is heat transfer. There has to be a way to get the heat out. Even two wires pushed or held together reduces their ability to lose heat. The fact that they melted together says they were touching. That made the problem worse. But if they were touching at a grommet the problem gets even worse yet. Add tape or conduit and the problem skyrockets. The best solution is bigger wire (less resistance, less heat, and better heat disappation. Even a fan will help. But fundamentally, that contraption is operating without a big enough safety factor. I'd increase the gauge and use a wire coating designed to handle more heat.

Also check your connections. Connection resistivity can also skyrocket the temperatures. Its the next weakest link in your system waiting to bite you.
 
Susquatch said:
I'd increase the gauge and use a wire coating designed to handle more heat
Click to expand...
That sounds eminently sensible.

At the same time, I'm concerned that the current sensor generates enough current to heat these wires - I'm going to have to go understand how these work instead of just "kinda knowing". Replacing with bigger wire requires disassembly into wrapped toroids which makes me loathe to go in there.
 
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