Question

For a C.T. the transformation ratio is given by which of the following relation?

(a) R = \(\frac{I_s}{I_p}\)

(b) R = \(\frac{I_p}{I_s}\)

(c) R = \(\frac{1}{I_p}\)

(d) R = Ip

I had been asked this question by my school teacher while I was bunking the class.

This interesting question is from Ratios of Instrument Transformers topic in division Extension of Instrument Ranges of Electrical Measurements

Answer 1

Right choice is (b) R = \(\frac{I_p}{I_s}\)

Easy explanation: In a current transformer, the transformation ratio is given by the ratio of the magnitude of the actual primary current to the magnitude of the actual secondary current.

R = \(\frac{I_p}{I_s}\)

where, R is the transformation ratio

       Ip is the actual primary winding current

       Is is the actual secondary winding current.