Nameplate current conversion

Transformer Full-Load Current Calculator

Calculate primary and secondary full-load current from transformer kVA, phase and line voltage without selecting a transformer.

Enter your values

Example values demonstrate the method; they are not product recommendations.

Your result

Enter measured or nameplate values to calculate.

Method

Single-phase current = VA ÷ voltage. Balanced three-phase line current = VA ÷ (√3 × line-to-line voltage).

Important limits

Rated current is not a protection or fault-current calculation. Impedance, vector group, inrush, harmonics, cooling and installation rules are excluded.

Technical reference

Read a transformer-current result correctly

The phase and voltage change the answer
Supply Full-load current formula
Single phase I = kVA × 1,000 ÷ voltage
Three phase I = kVA × 1,000 ÷ (√3 × line-to-line voltage)
Example rating100 kVA
Illustrative three-phase transformer.
Secondary voltage415 V
Line-to-line voltage.
Secondary current139.1 A
100,000 ÷ (√3 × 415). A calculated full-load reference.

Transformer full-load current is the transformer’s reference current at rated load. It is different from the rated current of one connected motor. Breaker, cable and motor-starter selection also need their own application checks.

Measurement guidance and calculation assumptions

Calculate primary and secondary full-load current for single-phase or three-phase transformers from kVA and voltage.

Estimate transformer full-load current with Vukar Automation's calculator. Enter the transformer rating and supply voltage shown on its label.

What to enter

Use current, project-specific values for transformer kVA, primary and secondary voltage and phase. Check every unit before calculating and compare like-for-like inputs.

How to use the result

Treat primary and secondary full-load current as calculated references. Nameplate data, taps, efficiency, protection, inrush and installation requirements need engineering review.

Before making a decision

Verify source measurements, equipment specifications and operating conditions. Have a qualified professional review the final selection, safety and installation requirements before purchase, connection or construction.