How much power does a unloaded 1A transformer use?

william chan

Gadgetman,

I know you have been playing with your wattmeter/joulemeter for some time know.
Suppose you have a 240v to 12v 1A adapter plugged in, how many watts does it consume when the secondary coil (12v) is not loaded?

Thanks.

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www.fd.com.my
www.mercedes.com.my

stamptrol

Without any specs or test results on the xformer we can only guess, but the only consumption is the copper loss in the primary and the eddy current losses in the iron core.
High quality large transformers can get that loss down to 1% or less of rated capacity. Small transformers, particularly mass produced wall wart type have losses of perhaps 5%.
A poster a few days a go had some actual measurements and it worked out to about $4.00 per year of losses.

Cheers,

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Tom Sisk

http://www.siskconsult.com
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