1600 kVA Transformer Full Load Current: Calculation and Sizing Notes
1600 kVA is one of the ratings that comes up again and again on industrial sites and large commercial buildings. Full load current is the figure the cable, the main breaker and the protection settings are all derived from, so it is worth getting right before anything is ordered.
The formula
For a three-phase transformer: I = P ÷ (√3 × V). P is the rating in volt-amperes, V is the line-to-line voltage, and √3 is 1.732. Every figure in the tables below comes straight out of it — you can reproduce them on a calculator.
1600 kVA at common voltages
| Voltage | Full load current |
|---|---|
| 400 V | 2,309 A |
| 415 V | 2,226 A |
| 6.6 kV | 140 A |
| 11 kV | 84 A |
| 13.8 kV | 67 A |
| 22 kV | 42 A |
| 24 kV | 38 A |
| 33 kV | 28 A |
Read the two sides separately. The 400 V and 415 V figures are the secondary current — at 1600 kVA that is over two thousand amps, which is normally carried on a busbar or on several cables in parallel rather than one large cable. The 11 kV through 33 kV figures are the primary current, and they are what the HV protection and the CT ratios are set from.
How it compares with neighbouring ratings
| Rating | At 400 V (secondary) | At 11 kV (primary) |
|---|---|---|
| 1000 kVA | 1,443 A | 52 A |
| 1250 kVA | 1,804 A | 66 A |
| 1600 kVA | 2,309 A | 84 A |
| 2000 kVA | 2,887 A | 105 A |
| 2500 kVA | 3,608 A | 131 A |
Useful when a project is still between two ratings: each step up in kVA moves the secondary current by roughly a quarter, which is usually the difference between one panel arrangement and the next one up.
What the number drives
- LV cable or busbar rating on the secondary side.
- Main breaker frame size and trip setting.
- Current transformer ratios for metering and protection.
- Termination and busbar ratings inside the panel.
- Voltage drop over the run to the main board.
Two things people get wrong
First, quoting a current without saying which side it is on. 1600 kVA is 84 A on an 11 kV primary and 2,309 A on a 400 V secondary — the same machine, two numbers that differ by a factor of twenty-seven.
Second, treating full load current as the finished cable size. Cable selection also takes the installation method, how many cables run together, ambient temperature and the permissible voltage drop. Full load current is where that calculation starts, not where it ends.
Send us the rating and the voltages on both sides and we will confirm the configuration, the impedance and the drawings.
Send us the specification
Rating, primary and secondary voltage, frequency, quantity and the application. We answer within one working day.
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