Plate rolls transformer getting extremely hot

While using an old set of Bertsch and Son plate rolls, a 5/8x12’ capacity, what I think is a transformer is getting hot. I have a tool sitting on top of the expanded metal cover that is always there that I use to line up the seam so the shell can be tacked after rolling and while it’s got warm it’s never gotten to a point where it was so hot it was uncomfortable, until a couple days ago.

I grabbed the handle on the tool that was sitting on the cover and it burnt the piss out of me. Now I know transformers will get warm and maybe even too hot to hold your hand on but I just shot it with a my temp gun and got a reading of 414 degrees. That’s seem a wee bit excessive but I could’ve wrong?

Are transformers suppose to get that hot?

I can’t figure out how to add pictures that I took of the piece the, what I think is a transformer or I would post them.

No, not supposed to get that hot. I'm not an electricals expert, but maybe you've got some damaged windings that are getting even worse as the 'former overheats more and more.

Gurus, can you Meg a transformer?

Or maybe you've got another fault that's causing an excess current draw? If the rest of the machine seems to be working correctly, I'd guess not...

I just shot it while rolling a bigger shell and got 570f and I shut it down

Open mesh ?

I think I've seen these with multiple step cam controllers, and you've got some big resistors in the box with open mesh.

Yeah... 414F is over 200C, where most transformers are limited to close to 100C to maybe 140C. And that is hot spot temperatures.

It is unusual for a transformer to be in an open-mesh topped box, they are usually quite well enclosed.

The resistors sound like a possibility. Maybe motor has a wound rotor? Or is it so old it is DC?

JST said:

Yeah... 414F is over 200C, where most transformers are limited to close to 100C to maybe 140C. And that is hot spot temperatures.

It is unusual for a transformer to be in an open-mesh topped box, they are usually quite well enclosed.

The resistors sound like a possibility. Maybe motor has a wound rotor? Or is it so old it is DC?

Click to expand...

That was it, "Wound rotor" motors, IIRC they had 4-5 speeds forward and reverse.

Big handled cam controllers, look like your driving a subway car.

I also suspect the heat is not coming from a transformer, but if it is transformers can fail with a short across one or two windings, which gets hot and degrades the insulation causing more shorts and more heat until the breaker trips.

When was the last time you took the covers off the controllers, the motors, and the resistors ?
And gave them a good cleaning with an air hose ?

My guess is a fan has failed if indeed it is a wound rotor motor with resistors inside a box.

Does the motor sound differently at a different speed? If one of the resistors is open circuit the other two would be overloaded.