Transformer Calculator
Calculate turns ratio, secondary voltage, current and power for ideal transformer circuits.
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V1/V2 = N1/N2 | I1/I2 = N2/N1
How do transformers work?
A transformer transfers electrical energy between two circuits through electromagnetic induction. The primary winding creates a changing magnetic field in the core, which induces a voltage in the secondary winding. The voltage ratio equals the turns ratio: V1/V2 = N1/N2.
In an ideal transformer, power is conserved: V1 × I1 = V2 × I2. This means a step-down transformer that halves the voltage doubles the current. Real transformers have losses from core hysteresis, eddy currents, and winding resistance, with typical efficiencies of 95–98% for power transformers and 80–90% for small signal transformers.
The turns ratio determines whether the transformer steps voltage up or down. N1/N2 > 1 is step-down (lower secondary voltage), N1/N2 < 1 is step-up (higher secondary voltage). A 1:1 ratio provides galvanic isolation without changing the voltage, useful for safety and noise rejection.
Turns Ratio (N1/N2)
V1 / V2 = N1 / N2Power (VA)
V1 × I1 = V2 × I2Key Points
- Voltage ratio equals turns ratio: V1/V2 = N1/N2
- Current ratio is inverse: I1/I2 = N2/N1
- Ideal power conservation: V1×I1 = V2×I2
- Real efficiency: 80–98% depending on size and type
Applications
- AC mains voltage conversion (step-up/step-down)
- Galvanic isolation for safety
- Impedance matching in audio and RF circuits
- Switch-mode power supply transformers