Transformer Voltage Regulation
VR = (Vnl − Vfl) / Vfl
Quick answer
This calculator solves VR = (Vno-load − Vfull-load) / Vfull-load × 100% for Voltage Regulation. With No-Load Voltage 12 V, Full-Load Voltage 26.4 V, the result is -54.55 %. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
Voltage regulation measures how much a transformer’s secondary voltage sags between no load and full load, expressed as a fraction of the full-load voltage. The drop is caused by the winding resistance and leakage reactance carrying the load current. A lower regulation percentage means a stiffer, better-regulated supply. Ideal transformers have zero regulation; real ones are typically a few percent.
Variables
- VR — Voltage regulation (fraction or %)
- Vnl — Secondary voltage at no load (V)
- Vfl — Secondary voltage at full load (V)
Practical Notes
Good distribution transformers achieve 1–3% regulation; small mains transformers may be 5–10%. Poor regulation forces the design to use a higher no-load voltage so the loaded output stays in spec.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| VR | Voltage Regulation | % | —, % |
| Vnl | No-Load Voltage | V | pV, nV, µV, mV, V, kV |
| Vfl | Full-Load Voltage | V | pV, nV, µV, mV, V, kV |
Step by step
- 1. What you know: No-Load Voltage 12 V, Full-Load Voltage 26.4 V
- 2. The relation: VR = (Vno-load − Vfull-load) / Vfull-load × 100%
- 3. Substitute: Vnl = 12 V, Vfl = 26.4 V
- 4. Result: Voltage Regulation = -54.55 %
Worked examples
Minimum range
Given: No-Load Voltage 0.33 V, Full-Load Voltage 0.726 V
Result: Voltage Regulation = -54.55 %
Low range
Given: No-Load Voltage 3.3 V, Full-Load Voltage 7.26 V
Result: Voltage Regulation = -54.55 %
Typical
Given: No-Load Voltage 12 V, Full-Load Voltage 26.4 V
Result: Voltage Regulation = -54.55 %
High range
Given: No-Load Voltage 0.23 kV, Full-Load Voltage 0.506 kV
Result: Voltage Regulation = -54.55 %
Maximum range
Given: No-Load Voltage 2.3 kV, Full-Load Voltage 5.06 kV
Result: Voltage Regulation = -54.55 %
Solving for each variable
Solve for Voltage Regulation
No-Load Voltage 0.33 V, Full-Load Voltage 0.726 V → -54.55 %
Solve for No-Load Voltage
Voltage Regulation 0.5 %, Full-Load Voltage 0.726 V → 0.7296 V
Solve for Full-Load Voltage
Voltage Regulation 0.5 %, No-Load Voltage 0.33 V → 0.3284 V
How Voltage Regulation changes with No-Load Voltage
| No-Load Voltage (input) | Voltage Regulation (result) |
|---|---|
| 1.2 V | -95.45 % |
| 3 V | -88.64 % |
| 6 V | -77.27 % |
| 9 V | -65.91 % |
| 12 V | -54.55 % |
| 18 V | -31.82 % |
| 24 V | -9.091 % |
| 48 V | 81.82 % |
| 84 V | 218.2 % |
| 120 V | 354.5 % |
The same result in other units
| Unit | Value |
|---|---|
| % | -0.5455 |
| % | -54.55 |
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<p><a href="https://vbatpower.com/formulas/transformer-voltage-regulation/">Transformer Voltage Regulation</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Transformer Voltage Regulation?
Use VR = (Vno-load − Vfull-load) / Vfull-load × 100%. With No-Load Voltage 12 V, Full-Load Voltage 26.4 V, Voltage Regulation works out to -54.55 %.
What is the formula for Transformer Voltage Regulation?
The formula is VR = (Vno-load − Vfull-load) / Vfull-load × 100%. Voltage regulation measures how much a transformer’s secondary voltage sags between no load and full load, expressed as a fraction of the full-load voltage.
How do you find No-Load Voltage when you know the other values?
Rearrange for No-Load Voltage: with Voltage Regulation 0.5 %, Full-Load Voltage 0.726 V, No-Load Voltage is 0.7296 V.
How do you find Full-Load Voltage when you know the other values?
Rearrange for Full-Load Voltage: with Voltage Regulation 0.5 %, No-Load Voltage 0.33 V, Full-Load Voltage is 0.3284 V.
What units does Transformer Voltage Regulation use?
Voltage Regulation is shown in %, %. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
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