For an ideal transformer, the electrical ratios follow the turns ratio:
a = Np / NsVp / Vs = Np / Ns = aIs / Ip = Np / Ns = a- Power balance estimate:
Vp × Ip ≈ Vs × Is
These equations ignore copper loss, core loss, leakage inductance, and voltage regulation.
- Select what you want to solve from the Solve for menu.
- Enter known turns, voltages, or a ratio
a. Use RMS values for AC. - Optionally add currents to estimate apparent power consistency.
- Press Calculate to show results above the form.
- Use Download CSV or Download PDF to export.
| Case | Np (turns) | Ns (turns) | Vp (V) | Vs (V) | a = Np/Ns | Type |
|---|---|---|---|---|---|---|
| Lighting supply | 1000 | 100 | 230 | 23 | 10 | Step-down |
| High voltage test | 500 | 2000 | 120 | 480 | 0.25 | Step-up |
| Isolation transformer | 800 | 800 | 230 | 230 | 1 | 1:1 isolation |
Transformer turns ratio for analysis and planning
A transformer’s turns ratio links winding geometry to voltage conversion. This calculator helps you compute a = Np/Ns, compare it with Vp/Vs, and estimate missing turns, voltages, or currents using ideal transformer relationships. It also flags mismatches that may indicate tap settings or measurement errors.
1) Core relationship: turns and voltage
In an ideal transformer, the voltage ratio equals the turns ratio: Vp/Vs = Np/Ns. For example, 230 V to 23 V implies a ratio near 10. If you enter turns and voltages together, the tool highlights disagreement to catch input errors.
2) Step-up, step-down, and 1:1 isolation
When a > 1, the secondary voltage is lower, so the unit is step-down. When a < 1, the secondary voltage is higher, so it is step-up. A value of 1 indicates 1:1 isolation, often used for safer servicing.
3) Typical field values and targets
Common industrial conversions include 230→24 V (a ≈ 9.58) and 120→12 V (a = 10). High-voltage test setups may use 120→480 V (a = 0.25). Using realistic targets helps you sanity-check turns counts and tap selections.
4) RMS inputs and measurement discipline
Enter RMS values for AC systems. If peak values are used accidentally, ratios shift by about √2, creating false mismatches. Measure no-load and loaded voltage separately; regulation under load can lower Vs a few percent even when the turns ratio is correct.
5) Current ratio and load impact
Ideal current ratio follows Is/Ip = Np/Ns. Stepping down voltage increases available secondary current, while stepping up voltage reduces it. Provide currents from the same operating condition as the voltages to keep results meaningful.
6) Apparent power balance check
The calculator estimates apparent power on both sides using Vp×Ip and Vs×Is. In a lossless model they match. Real units show lower secondary VA due to copper and core losses, so small mismatches can be normal.
7) Using the tool for design estimates
For repair or reverse-engineering, enter turns to compute voltages. For early design, enter target voltages to get a ratio, then choose turns based on core size and flux limits. The “Solve for” menu supports both workflows without extra steps.
8) Documentation and collaboration
Export CSV or PDF to share ratios, computed turns, and consistency checks with technicians or reviewers. Recording whether the transformer is step-up, step-down, or 1:1 reduces wiring mistakes and supports faster troubleshooting during commissioning and maintenance.
1) Can I find the turns ratio from voltages only?
Yes. If you know Vp and Vs (RMS), the calculator uses Vp/Vs to estimate a. You can then solve for missing turns if one winding’s turns are provided.
2) Why is my measured Vs slightly lower under load?
Real transformers have winding resistance and leakage inductance. As load current rises, voltage drops (regulation). Measure no-load and rated-load values separately to understand the difference.
3) Does this work for DC?
No. Standard transformers require changing flux, so they need AC or switching waveforms. DC can saturate the core and overheat the winding.
4) What does a “power mismatch” mean?
It compares Vp×Ip against Vs×Is. Large mismatches often indicate inconsistent measurements, different load conditions, or incorrect units. Small mismatches can be normal due to losses.
5) How do I tell step-up vs step-down?
If a > 1, it is step-down (Vs lower). If a < 1, it is step-up (Vs higher). Current moves inversely with voltage in the ideal model.
6) Can I use this for autotransformers?
You can estimate voltage ratio, but current relations differ because windings share conductors. Treat current and power checks as approximate rather than exact.
7) What values should I enter for best accuracy?
Use RMS voltages and currents measured at the same operating point. If possible, include turns (Np and Ns) to validate ratios from two independent sources.