Question

A (350 A/7A), 50 Hz current transformer has a primary bar. The secondary has a pure resistance of 1 Ω. It also draws a current of 5 A. The magnetic core requires 350 AT for magnetization. Find the percentage ratio error.

(a) 10.56

(b) -28.57

(c) 11.80

(d) -11.80

This question was posed to me by my school teacher while I was bunking the class.

Asked question is from Advanced Problems on Magnetically Coupled Circuits topic in chapter Resonance & Magnetically Coupled Circuit of Network Theory

Answer 1

The correct answer is (b) -28.57

To explain I would say: Im = 350/1 =350 A

Ip = \(((nI_s^2)^2 + (I_m^2)^2)^{0.5}\) = 490.05

Or, n = \(\frac{350}{7}\) = 50

∴ R = \(\frac{I_P}{I_S}  = \frac{490.05}{7}\) = 70

∴ Percentage ratio error = \(\frac{50-70}{70}\) × 100 = -28.57%.