Question

In a three-phase transformer, the load current is 139.1A, and the secondary voltage is 415V. What would the rating of the transformer be?

a) 50 kVA
b) 100 kVA
c) 150 kVA
d) 200 kVA

Answer 1

The rating of a three-phase transformer with a load current of 139.1A and a secondary voltage of 415V is calculated to be approximately 100 kVA, which is option (b).

Step-by-step explanation:

To calculate the rating of a transformer, you can use the following formula for a three-phase transformer: Rating (in VA) = √3 × V × I, where √3 is the square root of 3, V is the voltage, and I is the current.

In this case, the load current (I) is 139.1A, and the secondary voltage (V) is 415V. Plugging in the values, we get:

Rating = √3 × 415V × 139.1A = 1.732 × 415V × 139.1A ≈ 100 kVA

Therefore, the rating of the transformer would be 100 kVA, which corresponds to option (b).