Ideal Transformer Calculator

Ideal Transformer Calculations

Transformers transfer electrical power between circuits through magnetic coupling. In an ideal transformer, there are no copper or core losses, so input power equals output power. This calculator finds secondary voltage and primary current from primary voltage, turns ratio, and secondary load current.

Formulas

Voltage and turns are related by:

$$\frac{V_s}{V_p} = \frac{N_s}{N_p}$$

Power conservation gives:

$$I_s V_s = I_p V_p$$

From these relations, secondary voltage is $V_s = V_p \times (N_s/N_p)$ and primary current is $I_p = I_s \times (N_s/N_p)$ for a given secondary load current $I_s$.

Practical Notes

Real transformers have efficiency below 100% due to winding resistance and core losses. Use nameplate ratings and manufacturer data for installed equipment. Step-up transformers increase voltage and decrease current on the secondary side; step-down transformers do the opposite.

Frequently Asked Questions

What is an ideal transformer?

An ideal transformer has no losses. All input electrical power is delivered to the load on the secondary side.

How do I enter the turns ratio?

Enter Ns/Np directly, or switch to primary and secondary turns mode to enter coil counts. A ratio greater than 1 steps voltage up; less than 1 steps it down.

Why does primary current change with load?

As secondary load current increases, more power is drawn. The primary must supply matching power, so primary current rises proportionally.

Is secondary current the same as load current?

For a simple resistive load on the secondary, yes. This calculator treats the entered secondary current as the load current.

Does this work for three-phase transformers?

This tool uses single-phase ideal relations. For three-phase systems, apply per-phase values or use a dedicated three-phase calculator.

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Ideal Transformer Calculations

Formulas

Practical Notes

Frequently Asked Questions

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