Transformer Calculator

About Transformer Calculator

The Transformer Calculator computes turns ratio, secondary voltage, primary and secondary current, power, and impedance transformation ratio for electrical transformers. Enter the primary voltage and number of turns for both windings, with optional current or power values, to get a complete analysis with step-by-step MathJax formulas.

What Is a Transformer?

A transformer is an electromagnetic device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of a magnetic core with two (or more) coils of wire wound around it. The primary winding receives input power, and the secondary winding delivers output power at a different voltage level.

where \(V_1\) and \(V_2\) are primary and secondary voltages, \(N_1\) and \(N_2\) are the number of turns in each winding, and \(n\) is the turns ratio.

Key Transformer Equations

Voltage ratio: The voltage across each winding is proportional to the number of turns:

Current ratio: Current is inversely proportional to the turns ratio (for an ideal transformer):

Power: For an ideal transformer, power is conserved: \(P_{in} = P_{out}\). For real transformers with efficiency \(\eta\): \(P_{out} = \eta \times P_{in}\).

Step-Down vs. Step-Up Transformers

• Step-Down (N₁ > N₂) — reduces voltage, increases current. Common in power distribution (e.g., 120V from 12kV lines) and DC power supplies.
• Step-Up (N₁ < N₂) — increases voltage, reduces current. Used in power transmission to reduce line losses and in CRT/high-voltage applications.
• Isolation (N₁ = N₂) — provides galvanic isolation without changing voltage. Used in medical equipment, sensitive electronics, and safety applications.

Impedance Transformation

Transformers also transform impedance by the square of the turns ratio:

This property is widely used in audio systems (matching speaker impedance to amplifier output) and RF circuits (antenna impedance matching).

How to Use This Calculator

1. Enter primary voltage — Input the voltage applied to the primary winding (V₁) and select the unit.
2. Enter turns — Input the number of turns for the primary winding (N₁) and secondary winding (N₂).
3. Optional inputs — Provide primary current, power rating, or adjust efficiency to get current and power calculations.
4. Click Calculate — Press the button to compute all transformer parameters.
5. Review results — Examine the turns ratio, voltages, currents, power, impedance ratio, transformer diagram, and step-by-step formulas.

Practical Applications

• Power distribution — Step-up transformers transmit power at high voltage over long distances, then step-down transformers reduce it for household use.
• Electronic power supplies — Mains voltage is stepped down to low voltage (5V, 12V, etc.) for electronic devices.
• Audio equipment — Output transformers match vacuum tube or transistor impedance to speakers. Input transformers provide balanced signal isolation.
• Welding — Welding transformers step down voltage and step up current to create the high-current arc needed for welding.
• Measurement — Current transformers (CTs) and potential transformers (PTs) step down high voltages and currents for safe measurement.

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