[Amps] White Smoke

[Will Matney]

Hal,
If I recall, this was a heater transformer wasn't it, not the plate 
transformer? Before you send it back, let me know what the core is 
(C-Core or EI) and the measurements of the core, width, height, and 
depth. Also, what the secondary voltage and current rating is. I can 
then calculate the primary wire size that should have been used. The 
reason being, the magnet wire shouldn't have gotten hot enough to melt 
through that quick, I wouldn't think. When one is connected out of 
phase, one winding is bucking the other which is almost the same as an 
short. Within no time, the breaker should have kicked and or a fuse 
blowed if in the amp. This one wasn't but your breaker should have 
caught it. Generally when one is out of phase, as soon as the power hits 
it, it will create a loud hum, and within 1-2 seconds kick out the 
breaker or fuse. The wire size should have been large enough to handle a 
momentary overload such as this. By your description, the only thing 
that could have happened is the winding got hot and opened, thus the 
smoke. What I'm thinking could have happened is that they nicked a wire 
when they were making the coil, or made a bad connection at one of the 
leads. Then, when you powered it up, it just burnt in two, especially if 
it were out of phase and putting a load on the winding. On re-winding 
motors, the same wire size is generally used as in transformers. A 
similar result would have been the current drawn from what's known as 
"locked rotor current". This is when the shaft of the motor is froze and 
the coils are energized. I've never seen a motor burn out that quick 
either, with trying to start a locked rotor motor.

You mentioned some Linoleum catching on fire too. Your meaning some the 
transformer was setting on? Or the fish paper that the transformer is 
wrapped with? Those Dahl transformers are wrapped with regular blue fish 
paper for insulation. The black color you see is a black dye they 
purposely mix in the varnish. Theoretically, this is supposed to help 
take heat away from the windings. This black color also makes it hard to 
see anything burnt too!

When your winding transformers, each lead is attached after the coil is 
completed before the last wrap of fish paper is put on the coil. The 
worker will label each lead per the prints they are provided. On the 
primary leads for 240 Vac service, the start and stop of each winding 
determines the phase. If the worker got this mixed up, it was labeled it 
out of phase. Either or, what happened would not of been the fault of 
anything you did. I would say that transformer was probably never tested 
before it left the factory.

Will Matney