Question

A 25 KVA transformer has a voltage
ratio of
3300/400V, find
primary and and secondary current
​

Answer 1

First to note down the following:

N1N2=83458

Now calculate the induced voltage at the terminals of our secondary if the input to primary is 3300 V , simply we assume ideal transformer where:

V1V2=N1N2

Now V2 is:

V2=V1∗N2N1

V2=3300∗58834=229.496403≈229.5 V

Now assume you speak about 3-phase transformer then the current that will be drawn from the secondary winding is I2 where:

S=3–√V2I2

Now calculate I2 :

I2=S3–√V2

I2=50∗1033–√∗229.496403=125.786344≈126 A

If the transformer was single phase, just remove the 3–√ , and the current is:

I2=50∗103229.496403=217.868338≈218 A