Full Load Current Turns Ratio calculator for Transformer
Compute transformer full-load current for single/three-phase and find turns ratio a = Np/Ns = Vp/Vs = Is/Ip. Includes examples and quick reference tables.
full load current calculator transformer
Rated kVA, voltage give full-load current: single-phase I = S/V, three-phase I = S/ ( sqrt 3 VLL ). Is/Ip connects the primary and secondary currents in an ideal transformer with the turns ratio a = Vp/ Vs.
Formula & Table Summary:
- Turns ratio (ideal): a = Np/Ns = Vp/Vs = Is/Ip
- Single-phase FLA: I = S / V
- Three-phase FLA: I = S / (√3 × V_LL)
- Rearrangements: S = V × I (1φ), S = √3 × V_LL × I (3φ)
- Current scaling: Is = a × Ip, Ip = Is/a
transformer turns ratio calculator
This calculator determines transformer full-load current (FLA) on primary and secondary and compares them using the turns ratio. In a single-phase unit, full-load current is I = S/V. For a three-phase unit, I = S/(√3·V_LL). The ratio of the turns is a = Np/Ns = Vp/Vs = Is/Ip (ideal transformer), and therefore current is inversely proportional to voltage. Give rated kVA, voltage(s), and system phase to obtain Ip FL and Is FL immediately, and refer currents and impedances across sides with a to. Always use nameplate information and comply with the following standard protection size as specified by your code and coordination study.
single phase transformer FLA
| S (kVA) | Vp (V_LL) | Vs (V_LL) | a | Ip_FL (A) | Is_FL (A) |
|---|---|---|---|---|---|
| 100 | 11000 | 415 | 26.506 | 5.25 | 139.20 |
| 500 | 13800 | 480 | 28.750 | 20.93 | 601.04 |
| S (kVA) | Vp (V) | Vs (V) | a | Ip_FL (A) | Is_FL (A) |
|---|---|---|---|---|---|
| 25 | 2400 | 240 | 10.000 | 10.42 | 104.17 |
