Transformer Turns Ratio Calculator

A transformer's turns ratio describes how voltage is stepped up or down between the primary and secondary windings — it's a fundamental parameter for selecting, testing, and verifying transformers in electrical systems. Enter your transformer rating, number of phases, primary voltage, and secondary voltage into the Transformer Turns Ratio Calculator to get the turns ratio (Np:Ns). Secondary outputs include primary full load current, secondary full load current, and transformer type (step-up or step-down).

Results

Turns Ratio (Np:Ns)

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Primary Full Load Current

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Secondary Full Load Current

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Transformer Type

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Frequently Asked Questions

How to calculate a transformer's primary full load current?

The primary winding full load current is calculated using the formula: Ip = S / (√3 × Vp) for three-phase transformers, or Ip = S / Vp for single-phase transformers, where S is the transformer rating and Vp is the primary voltage.

How to calculate a transformer's secondary full load current?

The secondary winding full load current is calculated as: Is = S / (√3 × Vs) for three-phase transformers, or Is = S / Vs for single-phase transformers, where S is the transformer rating and Vs is the secondary voltage.

How to calculate a transformer's turns ratio?

The turns ratio is calculated as the ratio of primary voltage to secondary voltage: Turns Ratio = Vp / Vs. This ratio also equals the ratio of primary turns to secondary turns (Np:Ns).

What is the difference between step-up and step-down transformers?

A step-up transformer increases voltage from primary to secondary (turns ratio > 1), while a step-down transformer decreases voltage (turns ratio < 1). The type is determined by comparing primary and secondary voltages.

How do voltage units affect transformer calculations?

Voltage units (V, kV, MV) must be consistent in calculations. The calculator automatically converts units to ensure accurate results. Always verify that primary and secondary voltages are in appropriate units for your application.

Why is the phase configuration important in transformer calculations?

Single-phase and three-phase transformers use different current calculation formulas. Three-phase calculations include the √3 factor, while single-phase calculations do not. This significantly affects the full load current results.

What transformer rating units should I use?

Choose VA for small transformers (under 1000 VA), kVA for medium transformers (1-1000 kVA), and MVA for large power transformers (above 1000 kVA). The rating represents the apparent power capacity of the transformer.

How accurate are transformer turn ratio calculations?

Turn ratio calculations are highly accurate for ideal transformers. In real transformers, small variations may occur due to factors like winding resistance, leakage inductance, and core losses, but the calculated ratio provides an excellent approximation.