Question

A 1000/5 A, 50 Hz correct transformer has a secondary burden comprising a non-inductance of 2Ω. What is the ratio error, if the iron loss is 3 W and magnetizing mmf is 250 A?

(a) 4%

(b) 5.7%

(c) 3.6%

(d) 4.8%

I have been asked this question in an online quiz.

My enquiry is from Advanced Problems on C.T. and P.T. in section Extension of Instrument Ranges of Electrical Measurements

Answer 1

Right choice is (b) 5.7%

Best explanation: E = \(\frac{10}{200}\) V

I = 60 A

I = \(\frac{mmf}{N_P}\) = 250 A

Actual rating R = 200 + \(\frac{60}{5}\) = 212

So, percentage ratio error = \(\frac{K_n-R}{R}\) × 100 = \(\frac{200-212}{212}\) × 100 = 5.7%.