A 2 kVA, 200/100 V, 400 Hz transformer is desired to be used at a frequency of 50 Hz. What will be the voltage rating of the transformer at reduced frequency if the flux density remains constant?

Question

Question

This question was previously asked in

SSC JE Electrical 16 Nov 2022 Shift 3 Official Paper

Answer 1

The correct answer is option 1):(25 V)

Concept:

During the operation of the transformer, for the exciting current to remain the same the flux must be constant.

ϕ_m = constant

ϕ_m ∝ v/f

\(\frac{{{V_1}}}{{{f_1}}} = \frac{{{V_2}}}{{{f_2}}}\)

Calculation:

Given that,

f₁= 400,

V₁ = 200

f₂ = 50 Hz

\({V_2} = \frac{{{f_2}}}{{{f_1}}} × {V_1}\)

= \(50 \over 400\) × 200

= 25 V