How much current will flow through the primary?

Question

Here we have a 480 to 120 volt 500 watt transformer. Hooked up is a cooling fan that draws .17 amps what is the current flow in the 480 (primary) side of the transformer.

Answer 1

With such a large transformer compared to the size of the load, the magnetizing current and losses could cause the actual primary current to be as much as twice the calculated value for an ideal transformer.

Answer 2

I assume that the 0.17 amps flowing through the 120V side (secondary).

Then the calculation as follows,

V2/V1  =  I1/I2

120/480  =  I1/0.17

therefore,

I1  = (120/480) * 0.17

So the current in primary would be  0.0425 Amps