Calculator
A simple calculation every electrical engineer, technician, and maintenance professional should know:
How much current can a 1500 kVA, 3-phase transformer deliver at 415 V?
Let’s calculate it step by step.
Given
• Transformer rating: 1500 kVA
• System: 3-phase
• Secondary voltage: 415 V
• √3 ≈ 1.732
Formula
For a 3-phase transformer:
I = S / (√3 x V)
Where:
I = Full-load current (A)
S = Apparent power (VA)
V = Line-to-line voltage (V)
Calculation
I = 1500000 / (1.732 x 415)
I ≈ 2088 A
Full-load secondary current ≈ 2.09 kA
Engineering Check
The same transformer rating gives different full-load currents at different voltages.
- Higher voltage → lower current
- Lower voltage → higher current
This relationship is fundamental when sizing cables, busbars, circuit breakers, protection systems, and switchgear.