This question was previously asked in

ISRO (SDSC) Technician B (Electrical) April 2018 Official Paper

Option 1 : 160 A

__Concept__:

From the MMF balance equation of a transformer:

\(\frac{{{V_1}}}{{{V_2}}} = \frac{{{N_1}}}{{{N_2}}} = \frac{{{I_2}}}{{{I_1}}}\) ......(1)

Also, the rated power can be written as:

**P (MVA) = √3 V _{L} × I_{L}**

In a transformer, the current or the voltage steps up and down. But the power transferred is always equal.

__Application__:

Given-

Power = 3 MVA. (Full load rated power)

V1 = 11 kV

V2 = 433 V

We can write:

3 × 10^{6} = √3 × 11 × 10^{3} × I1

I_{1} = 157.45 A

**I _{1} = 160 (Approx)**