Electronics > Beginners
Transfo lamination bolts super hot at 20 min and no-load (solved)
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Cliff Matthews:
I tried the heat shrink on one bolt but it wouldn't fit, so I got some Teflon plumbers tape and it works just fine!
Thanks everyone! As John Candy and the Bobsledding Jamaican's used to say, "Cool Runnin"  8)
amyk:
You are lucky you didn't melt anything. A single turn is going to have a ridiculous amount of current flowing through it at a very low voltage --- probably only limited by the resistance of the loop itself. I wouldn't be surprised if those bolts were passing 100A+.
Cliff Matthews:

--- Quote from: amyk on March 05, 2019, 01:24:10 am ---You are lucky you didn't melt anything. A single turn is going to have a ridiculous amount of current flowing through it at a very low voltage --- probably only limited by the resistance of the loop itself. I wouldn't be surprised if those bolts were passing 100A+.

--- End quote ---
True. It's possible only a few lamination's were touching the bolt since the 5 amp breaker on the Variac didn't trip? I've had this 15 pound beast idling on the bench all evening at 122v - it's quiet and still only mildly warm. I bought both for only $25  :-+
TERRA Operative:
I would go for Kapton tape over the Teflon tape, the Teflon tape is pretty soft and weak and may wear through in a relatively short time with the vibration of the transformer (even a tiny bit of vibration could eventually wear through).
Cliff Matthews:

--- Quote from: TERRA Operative on March 05, 2019, 06:56:30 am ---I would go for Kapton tape over the Teflon tape, the Teflon tape is pretty soft and weak and may wear through in a relatively short time with the vibration of the transformer (even a tiny bit of vibration could eventually wear through).

--- End quote ---
I'll buy Kapton tape soon but Hammond (a notable mfg.), only thought it necessary to isolate one end. They could have been in error, so I triple wrapped the full length of all bolts and re-installed the fiber washer. It's run all night without further rise in temp.

Today I'll rewire the other unit, idle it for 30-minutes and if all goes fine, both can drive 300 watt resistive heater loads for an hour with the both 50v windings on each in parallel. That'll warm-up my shop (I need it, today we have -17C outside..)
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