Question

A 500 A, 50 Hz current transformer has a bar primary. The secondary burden is a pure resistance of 1 Ω and it draws a current of 5 A. If the magnetic core requires 250 Ampere-turn for magnetization, the percentage ratio error is __________

(a) 10.56%

(b) -10.56%

(c) 11.80%

(d) -11.80%

I got this question in examination.

This is a very interesting question from Advanced Problems on Error Analysis in Electrical Instruments topic in section Measurement of Resistance of Electrical Measurements

Answer 1

The correct answer is (b) -10.56%

Best explanation: IM = 250/I = 250 A

Ip

Or, R = \(\frac{V^2}{R} \)

∴ R = ± (2 × 1.5 + 5) = ± 8%.