Basic electrical power consumption in Amps

What circuit breakers? You mean those annoying switch looking thing that keeps turning itself off? Just wedge a screw in the switch gear, it'll solve those pesky problems!

;)

Jamie

I doubt any system would ever be *perfectly* balanced, (especially with thermostatically controlled devices), but if things are wired properly, I could see it being close to a balanced situation. However, in the case described here, I'd have my doubts of any real balance. Like I said, trailer homes were added later, that large community center was built in the last decade and was built where a few old houses were demolished, when they likely just hooked it to the same pole without giving much thought to the transformer size..... The engine repair shop was built in the last year or two, and was wired to that same pole.... and so on....

This assumes, of course, that copper losses (I^2 * R) are the source of heating, and that the overall rating is dependent on heat limitations. There are also core losses (which go DOWN when you draw secondary current), so the situation isn't exactly as the model would suggest. Also, there's a significant variation in air temperatures around here, so the season of the year is an important part of the overheating scenario. You can draw extra current in winter, if it's just a cooling issue.

Well, maybe a tiny bit. Utility transformers tend to have low core losses, so as to not waste energy. I did state some assumptions, and wouldn't pretend to have an exact solution. But the available single-side load is certainly greater than 104 amps. My "better" posted calculation was about 170.

What do you calculate?

so the situation

variation in

cooling

Pole pigs tend to blow up in the summer, with hot ambient, sunshine, and high a/c loads.

Its a bit more complicated than that. It depends on whether the transformer manufacturer has made any allowances for unbalanced loads in their secondary half windings. And where the limiting hot spot temperature will occur (primary or secondary).

If there is no allowance for unbalance, then either half of the secondary reaching 104 Amps will cause a maximum temp rise condition in that half winding. However, if the secondary windings have been overdesigned for maximum unbalance (208 A on one side, 0 A on the other), then its likely the thermal limitation of the primary winding will be reached at 25 kVA.

Obviously, if you only load one side, the loaded secondary half will be the thermal limit. Primary current will be less than full rated power.

Utility transformers are usually oil filled so have pretty good interior cooling. You are assuming zero shared cooling among windings, which isn't realistic.

My guess is around 150 amps one-side for reasonable heating.