Question

What is the formula of the ratio error in the current transformers?

(a) ratio error = turns ratio – regulation / regulation

(b) ratio error = turns ratio + regulation / regulation

(c) ratio error = turns ratio * regulation / regulation

(d) ratio error = 1 / turns ratio * regulation

This question was posed to me by my school principal while I was bunking the class.

Question is taken from Errors topic in section Design of Current Transformers (CT) of Design of Electrical Machines

Answer 1

The correct answer is (a) ratio error = turns ratio – regulation / regulation

For explanation I would say: First the turns ratio is calculated. Next the regulation of the current transformer is obtained and on substitution gives the ratio error.