Transformer Calculator

Analyze voltage, current, impedance transformation, and power relationships

Primary Side

Primary Voltage (V1) Volts

Turns Ratio N1 : N2

Primary Current (I1) - Calculated Amps

Load Impedance (ZL) Ω (Ohms)

Secondary Voltage

520V

Secondary Current

26A

Power Relationship

YesP1 = P2

Transformer Type

Step-Down

Transformer Diagram

Transformer Equations

Voltage Relationship: V1 / V2 = N1 / N2

Current Relationship: I1 / I2 = N2 / N1 (Inverse)

Power Relationship: P1 = P2 (Ideal transformer, no losses)

Impedance Reflection: Z_reflected = (N1/N2)² × Z_load

Impedance Transformation

Reflected Impedance (Primary Side)

Z_reflected = (400/50)² × 20 = 6400 Ω

The load impedance appears much higher on the primary side due to the square of the turns ratio.

kVA Rating & Maximum Currents

Transformer kVA Rating kVA

Max Primary Current

24A

Max Secondary Current

192A

Common Transformer Examples

Doorbell Transformer

120V step-down to 12V, 20VA typical. Calculate secondary current if load is 10Ω.

Distribution Transformer

4160V to 480V, 150kVA rated. What are the maximum currents?

Control Transformer

480V to 120V, 5kVA. Find impedance reflection of 150Ω load.