Question

A 200/1 Current Transformer (CT) is wound with 400 turns on the secondary on a toroidal core. When it carries a current of 180 A on the primary, the ratio is found to be -0.5%. If the number of secondary turns is reduced by 1, the new ratio error (in %) will be? (a) 0.0 (b) -0.5 (c) -1.0 (d) -2.0 I got this question in an online interview. This interesting question is from Problems Involving Coupling Coefficient topic in division Resonance & Magnetically Coupled Circuit of Network Theory Select the correct answer from above options network theory questions and answers, network theory questions pdf, network theory question bank, network theory gate questions and answers pdf, mcq on network theory pdf, gate network theory questions and solutions, network theory mcq Test , ies network theory questions, Network theory Questions for GATE EC Exam, Network Theory MCQ (Multiple Choice Questions)

Answer 1

Right answer is (c) -1.0 To explain I would say: Turn compensation only alters ratio error n=400 Ratio error = -0.5% = – \frac{0.5}{100} × 400 = -2 So, Actual ratio = R = n+1 = 401 Nominal Ratio KN = \frac{400}{1} = 400 Now, if the number of turns are reduced by one, n = 399, R = 400 Ratio error = \frac{K_N-R}{R} = \frac{200-200}{200} = 0.