Current transformers usually have a secondary winding rating of

A. 5 A
B. 20 A
C. 50 A
D. 100 A

Answer: A. 5 A

Explanation:
  • The current Ratio Also known as the Turns Ratio (in general terms) is the ratio of the primary current to the secondary current. 
  • This value is obviously equal to the ratio of number of turns in the primary and secondary coils. The current ratio of a CT is usually high. The secondary current ratings are typically 5A, 1A and 0.1A. 
  • The corresponding current primary ratings vary from 10A to 3000A or more.
  • However, it is important to note that 100/5 rating and 20/1 rating of Current Transformers are not the same, even though their current ratios are equal. 
  • These rating numbers actually represent the absolute values of “input/output current rating”.
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