In Three Phase Transformer, The load Current is 139.1 A, and Secondary Voltage is 415 V. The Rating of the Transformer would be:
100 kVA
Calculating Three Phase Transformer Rating (kVA)
To determine the rating of a three-phase transformer, we use the formula for apparent power in a three-phase system.
The formula for the apparent power (S) of a three-phase transformer is given by:
\(S = \sqrt{3} \times V_L \times I_L\)
Where:
- \(S\) is the apparent power in Volt-Amperes (VA) or kilo-Volt-Amperes (kVA).
- \(V_L\) is the line voltage in Volts (V).
- \(I_L\) is the line current in Amperes (A).
From the question, we are given the following values:
- Load Current (\(I_L\)) = 139.1 A
- Secondary Voltage (\(V_L\)) = 415 V
Now, we can substitute these values into the formula to calculate the apparent power:
\(S = \sqrt{3} \times 415 \text{ V} \times 139.1 \text{ A}\)
We know that \(\sqrt{3} \approx 1.732\). So, the calculation becomes:
\(S \approx 1.732 \times 415 \times 139.1 \text{ VA}\)
\(S \approx 1.732 \times 57626.5 \text{ VA}\)
\(S \approx 99801.778 \text{ VA}\)
To express the rating in kVA, we divide the result by 1000:
\(S \approx \frac{99801.778}{1000} \text{ kVA}\)
\(S \approx 99.80 \text{ kVA}\)
Comparing this calculated value with the given options:
- 50 kVA
- 57.72 kVA
- 100 kVA
- 173 kVA
The calculated value of approximately 99.80 kVA is closest to 100 kVA.
Therefore, the rating of the transformer would be approximately 100 kVA.
Important Questions from Three Phase Transformer Basics
Three-phase transformer contains-
Which type of connection is used for both large voltage and low voltage rating transformers?
The core of a three-phase, 50 Hz, 1000/400 V delta/star: 300 kVA core type transformer operated with a flux of 0.04 wb. Find the EMF per turn.
A three-phase transformer has 600 primary turns and 200 secondary turns. If the supply voltage is 1000 V, find the secondary line voltage on no-load when the windings are connected in star–delta.
A three-phase, three winding Δ/Δ/Y (1.1 kV/6.6 kV/400 V) transformer is energized from AC mains at the 1.1 kV side. It supplies 900 kVA load at 0.8 power factor lag from the 6.6 kV winding and 300 kVA load at 0.6 power factor lag from the 400 V winding. The RMS line current in ampere drawn by the 1.1 kV winding from the mains is ___________. (Give the answer up to one decimal place.)
