Question

The primary of a 200/1 A, 5 VA, 0.8 PF current transformer (CT) carries 100 A. The secondary current is 0.495 A. The ratio error of the CT is

• A. -1.0%
• B. -0.5%
• C. +0.5%
• D. +1.0%

Answer 1

The correct option is A -1.0%

Nominal ratio,

$k_n=\frac{200}{1}=200$

Actual transformation ratio,

$R=\frac{I_P}{I_S}=\frac{100}{0.495}$

= 202.020

$\text{Ratio error}=\frac{\text{Nominal ratio - Actual ratio}}{\text{Actual ratio}}\times 100$

$=\frac{200-202.020}{202.020}\times 100$

= -1.0%