Transformer Calculator
Calculate transformer turns ratio, output current, and input current from voltage and power ratings.
Essential for electrical design.
Transformer Specifications
Transformer calculations relate input voltage, output voltage, power, turns ratio, and current.
Turns Ratio:
Turns Ratio = Input Voltage / Output Voltage = N1 / N2
Current (assuming ideal transformer):
Input Current = Power (VA) / Input Voltage
Output Current = Power (VA) / Output Voltage
Power relationship:
Input Power = Output Power (ideal)
Input Power = Output Power / Efficiency (real-world)
Typical transformer efficiencies:
- Small transformers (< 100 VA): 85–90%
- Medium transformers (100–1000 VA): 90–95%
- Large transformers (> 1000 VA): 95–98%
Common applications:
- Step-down: 240V to 120V, 120V to 24V, 120V to 12V
- Step-up: 120V to 240V, 12V to 120V
- Isolation: 120V to 120V (1:1 ratio)
Note: Real transformers have losses from core hysteresis, eddy currents, and copper resistance. Actual current draw will be slightly higher than calculated.