What the...

[ptonsparky]

I wired two control transformers today, exactly the same. They came with factory wired primary fuse holders and an optional secondary fuse holder. Transformer 1 worked perfectly. Transformer 2 blew the primary fuses immediately. Loads were identical with no faults. 150VA 480 to 120. X2 grounded on each. What was wrong?

 

[GoldDigger]

Internal short to ground on the secondary? Turn to turn or turn to ground short on primary?

 

[kwired]

I have to agree with golddigger at this point, maybe defective or damaged and is a internal ground fault or turn to turn short, either winding.

Other possibility is it was a good unit but for whatever reason (made late on friday) it got marked wrong and is not actually 480 x 120.

 

[synchro]

I wired two control transformers today, exactly the same. They came with factory wired primary fuse holders and an optional secondary fuse holder. Transformer 1 worked perfectly. Transformer 2 blew the primary fuses immediately. Loads were identical with no faults. 150VA 480 to 120. X2 grounded on each. What was wrong?

Transformer 2 fuse holder was factory wired to the wrong place if there's a 480V / 240V primary?

 

[ptonsparky]

Transformer 2 fuse holder was factory wired to the wrong place if there's a 480V / 240V primary?

Close, but not quite. A simple continuity check confirmed my helps suspicion.

 

[ptonsparky]

It works now.

 

[Dennis Alwon]

One lead was labelled incorrectly?

 

[ptonsparky]

The xfmr labels were applied to the wrong sides. HV was on the LV side. Factory fuse block was connected per diagram but unfortunatly to the wrong side. Goes to show that those instructions are just another mans opinion. That led to my question about what the voltage would have been, however briefly, in the Engineering section. It took out an electronic temperature controller.

 

[kwired]

The xfmr labels were applied to the wrong sides. HV was on the LV side. Factory fuse block was connected per diagram but unfortunatly to the wrong side. Goes to show that those instructions are just another mans opinion. That led to my question about what the voltage would have been, however briefly, in the Engineering section. It took out an electronic temperature controller.

Like I said earlier, "made late on friday"

They possibly do an energized test of the coils, but might be before fuse block is installed

 

[PaulMmn]

The building I work in we had a snake crawl into the transformer and short out at least 1 winding. Lost partial power to the building. The snake did NOT survive!

 

[GoldDigger]

At Stanford we had the usual squirrel (bushy tailed rat!) climb into a 13k roll out breaker. Took awhile to clean all the carbon out of the enclosure.

 

[Jraef]

It works now.

It does? Nothing in the transformer fried, no flashover? I'm surprised.

 

[ptonsparky]

It does? Nothing in the transformer fried, no flashover? I'm surprised.

Good current limiting fuses and not overly large. The only thing I can blame.