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________________ | _____|_____ ______ | | | R1 and R2 used as a )|| __| | | 120vac )||(8vac R1 R2 test load to )||(7 Turns 14 Ohms 21 Ohms 6A )||(__ | | determine output amps. ______)|| | | | | |___________| 50 Turns |________________|

This schematic depicts a transformer under load for testing purposes. I scoured the web in search of a high current dummy load, no luck! I came up with the Idea of using 2 heating elements (R1 and R2) wired in parallel to reduce the total load resistance.

The result was surprising. I expected a good deal of heat but, the elements didn't even warm. The drawback is, how do I use the resulting data to determine the actual circuit amperage. These are the figures:

OCV: 8.1v Total secondary load resistance: 8.5 ohms Secondary current (clamp-on meter): 1.02 Amps Primary current under load: 8.3 Amps

SOS

Bill Bowden · Accepted Answer

I don't think you have enough turns on the primary, 8.3 amps is way too high, the transformer core is probably saturating. Primary current should be less than 1 amp.

The formula is Erms= 4.44 FNAB, where F=60, N=turns, A= cross sectional core area in sq meters, and B= flux density, somewhere around 1 for transformer steel.

So you should be able to figure out how many turns you need from the size of the core. But this is a minimum figure to avoid saturating the core, adding more turns will further reduce the current.

-Bill

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