Question

A 4 kva, 400 v/200 v single phase transformer has resistance of 0.02 p.U and reactance of 0.06 p.U. The resistance and reactance referred to hv side are

Answer 1

The bases of physical transformer resistance (T/F). So the induction between the two circuits with a common magnetic field in a statistical device.

The applied voltage V1 opposes E1,

While E2 provides the second output voltage V2.

E1/E2 = I2/I1 = T1/T2

R2+jX2=0.02 ohm+j0.06 ohm

a=V2/V1=200/400=0.5

R2'+jX2'=(R2+jX2)/(a^2)=0.08 ohm and 0.24 ohm

The resistance and reactance referred to hv side is 0.08 ohm and 0.24 ohm

Answer 2

V₁I₁ = V₂I₂

Z₁ = V₁/I₁

Z₂=V₂/I₂

V₁ = 400 V

V₂ = 200V

I₁ = P/V₁ = 4/400

I₂ = P/V₂ = 4/200

Z₁ =  400/(4/400) = 40000

Z₂ = 200/(4/200) = 10000

Z₁ = 4Z₂

Primary side is HV side

4 * 0.02 = 0.08 pu

4 * 0.06 = 0.24 pu