Transformer VA Rating Calculator

Values this page needs

Identify RMS, average, peak, and rectified quantities explicitly. If operating conditions changed between readings, calculate separate cases.

Convert units once, retain the original reading, and verify the converted magnitude. When that related quantity matters, continue with Generator Load Percentage Calculator.

Secondary voltage

Default example: 24 V. Enter secondary voltage in V.

Secondary current

Default example: 8 A. Enter secondary current in A.

How the result is calculated

The arithmetic is based on VA = V × I. The formula draws on Secondary voltage and Secondary current.

For the example shown, apparent power equals 192.00 VA. Treat that value as a demonstration, not a recommendation.

Calculate apparent power from secondary voltage and secondary current. For the companion autotransformer winding rating calculation, open Autotransformer Rating Calculator.

Applying the result

The primary answer, Apparent power, describes only the entered scenario. Compare it with a no-load, nominal-load, and limiting-load case.

A result without its source conditions is difficult to compare or audit. If you also need CT burden, continue with Current Transformer Burden Calculator.

Using the answer downstream

Record secondary voltage and secondary current with apparent power. Include the operating state and data source.

Transfer apparent power at its stored precision for dependent calculations. Round at the final reporting step.

Practical limits

Multiple windings require a combined loading check.

Further engineering review can cover leakage inductance, parasitic capacitance, saturation, switching transients, and cooling. Resolve material omissions before selecting a standard size or rating.

Record waveform, frequency, load level, and winding or device temperature. Continue to Current Transformer Ratio Calculator if primary current is also needed.

A final reasonableness check

Review secondary current and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.

Use apparent power alongside voltage stress, current stress, ripple, loss, regulation, and temperature. Preserve the unrounded number until all dependent calculations and comparisons are complete.

If uncertainty remains, calculate labeled low and high cases. Include leakage inductance, parasitic capacitance, saturation, switching transients, and cooling when those effects can change the decision.

Questions from practical use