Electrical · Free Calculator
Transformer Turns Ratio Calculator
Use the ideal transformer equations to relate primary and secondary voltage, turns and current.
Turns ratioVoltage ratioCurrent ratioIdeal transformer
V
V
turns
A
Turns ratio9.5833 : 1
Secondary turns96
Secondary current4.792 A
Volts per turn0.25 V
Power (ideal)115 VA
How this result was calculated
- a = Vp ÷ Vs = 230 ÷ 24 = 9.5833
- Ns = Np ÷ a = 96, Is = Ip × a = 4.792 A
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Ideal Transformer Equations
Vp ÷ Vs = Np ÷ Ns = Is ÷ Ip = a
Worked example
A 230/24 V control transformer has a ratio of 9.58. With 920 primary turns it needs 96 secondary turns, and 0.5 A primary current corresponds to 4.79 A secondary.
Key insight: real transformers have a slightly higher no load secondary voltage than the rated value, because the rating is stated at full load after internal voltage drop.
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Frequently Asked Questions
What is the turns ratio of a transformer?
The ratio of primary to secondary turns, which equals the voltage ratio in an ideal transformer.
How is current related to the turns ratio?
Current is inversely proportional: stepping voltage down by 10 steps current up by 10.
How is turns ratio tested?
With a TTR tester, which applies a low voltage to the primary and measures the secondary to confirm the ratio within about 0.5 %.
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