In a 1-phase 250 / 3000 V, 50 Hz transformer, if the EMF per turn is 8 V and I_LV = 400 A, determine the LV and HV side turns and power rating of the transformer.

Question

Question

This question was previously asked in

SSC JE EE Previous Paper 10 (Held on: 10 Dec 2020)

Answer 1

Concept :

Transformation Ratio :

Transformation ratio is defined as the ratio of secondary voltage to the primary voltage.
It can also be defined as the ratio of the number of turns in the secondary winding to the number of turns in the primary winding.
It can also be related to the current flowing in the primary winding to the current flow in the secondary winding.
It is represented by the letter ‘K’

K = (E₂/ E₁) = (N₂/ N₁) = (I₁ / I₂)

Calculations :

Given E_LV= 250 V, E_HV = 3000, I_LV = 400 A,

Emf per turn = 8 V

E_LV = N_LV × emf per turn

∴ N_LV = E_LV/ emf per turn

Similarly N_HV= E_HV/ emf per turn

N_LV = 250 / 8 = 32 (aprox)

N_HV= 3000 / 8 = 375

Power rating P = E_LV × I_LV= 250 × 400 = 100 kVA