Voltage regulation is the percentage drop in secondary voltage under load: Reg% ≈ x·(uR·cosφ + uX·sinφ). Here, uR = (Pk/S)·100, uX = √(uk²−uR²). For example, for 1000 kVA, uk = %6, Pk = 10.5 kW, full load, cosφ 0.9, uR ≈ %1.05, uX ≈ %5.91, regulation ≈ %3.52.
uR = (Pk/S)·100 · uX = √(uk²−uR²) · Reg ≈ x·(uR·cosφ + uX·sinφ)
Example calculation: 1000 kVA, UK %6, Pk=10.5 kW, full load, cosφ 0.9 → uR ≈ %1.05, uX ≈ %5.91 → regulation ≈ %3.52 (400 V → ≈ 386 V).
Transformer Voltage Regulation (%)
Calculate the secondary voltage drop (regulation) under load from the short-circuit voltage and copper loss.
Regulation
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uR (resistive)
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uX (reactive)
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Notes: uR = (Pk/S)·100, uX = √(uk²−uR²), Regulation ≈ x·(uR·cosφ + uX·sinφ) (x = loading ratio). It is a first-order approach. (Second-order term omitted, inductive load assumed). Pk and uk are taken from the transformer label. The exact value is determined using the full equivalent circuit.
How is it calculated?
- Enter the transformer power (kVA) and short-circuit voltage (uk %).
- Enter the total load copper loss (Pk) and load (%) from the label.
- Enter cosφ and secondary voltage and click Calculate.
Frequently Asked Questions
What is voltage regulation?
It is the percentage drop in the secondary voltage of a transformer when it switches from no-load to full load; a lower value is better.
What does the regulation depend on?
It depends on the load ratio, short-circuit voltage (uk%), load power factor, and the resistive/reactive components (uR, uX) of the transformer.
What is the difference between inductive and capacitive loads?
With an inductive (lagging) load, the voltage drops (positive regulation); with a capacitive load, the voltage may rise (negative regulation).
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