Hey. Im currently doing a bit of revision for an exam and I am struggling on the following question:

I understand the whole voltage/current/power/impedance ratio stuff, but cant seem to find any information on calculating efficiencies using the resistances or the transformer core losses. Any Suggestions?

Hey. Ive found a bit more information regarding copper losses in transformers. It states:

I would think given the question that the asnwer would be:

P = VI ∴ I = P/V

For the primary:
500/230 = 2.27 Amps

For the secondary:
500/24 = 20.83 Amps

Copper loss for primary:
2.27^{2} x 0.05 = 0.258 W

Copper loss for secondary:
20.83^{2} x 0.01 = 4.34 W

Total Copper Loss:
0.258 + 4.34 = 4.598 W

Total loss including core loss:

4.598 + 0.07 = 4.668 W

Total efficiency =
(500-4.668)/500 = 0.9907 = 99.07% efficient.

The problem with this is if we were only getting an efficiency of 99.07% the secondary wouldnt be developing 20.83 Amps! Does anyone know how to actually solve this question?

@ Maths:
I skimmed through this pretty fast but I would say that you should not have 500 watts for both the primary and secondary. With any efficiency of less than 100% you will naturally get you a lower secondary current than 20.83.

See this is where I am getting confused. If the input power is 504.668W instead of 500W wouldnt that make the current and thus the losses higher on the primary winding??