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A 50 Hz, bar primary CT has a secondary with 500 turns. The secondary supplies 5 A current into a purely resistive burden of 1 Ω. The magnetizing ampere-turns are 200. What is the ratio error at full load, if the iron loss is 1.5 W and magnetizing mmf is 100 A?(a) Zero(b) 45 μWb(c) 25.5 μWb(d) 100 μWbI have been asked this question in an interview for job.This key question is from Advanced Problems on C.T. and P.T. in portion Extension of Instrument Ranges of Electrical Measurements

Answer»

Right ANSWER is (B) 45 μWb

The explanation: Voltage induced in the secondary,

ES = IS × ZS = 5 V

ES = 4.44 f ∅ N

∴ ∅ = \(\frac{E_S}{4.44 \,f \,N} = \frac{5}{4.44 \,f \,N}\) = 45 μWb.



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