Guessing the power of a transformer


2010-03-07 9:59 pm
Hi all,

I have a power transformer that outputs 17-0-17 AC when plugged on 120V. Is there a way to measure, estimate or calculate the power of this transformer? I have absolutely no information other than the RMS power of the amplifier it came from : 2 x 16 watts in 8 ohms and 2 x 20 watts in 4 ohms.



2010-03-11 10:43 pm
You can weigh the transformer and compare with any transformer catalog. I have one right here if you tell me the weight and mains frequency.

If you can peel back the insulation and measure the gauge of the secondary winding you can look in a wire table to find the maximum current, based on a figure of about 600 circular mils per Ampere.

If the amplifier can supply a total of 40 Watts, figure 50% efficiency and add a few Watts for the other circuits, you will end up with about 85 Watts total. So about 5 Amperes secondary current may be close.