Power calculator
Transformer
The same flux threads both coils: volts go as the turns, amps the other way.
Free. It runs in your browser: nothing to install.
The example, worked out
Given
- Primary voltage
- 230 V
- Primary turns
- 1000
- Secondary given by
- Its turns
- Secondary turns
- 52
- Secondary current
- 2 A
Working
- volts follow the turns
- amps go the other way: the power is the same on both sides
Results
The formulas
- Vs / Vp = Ns / Npvolts follow the turns
- Ip = Is × Ns / Npamps go the other way
- Zp = (Np / Ns)² × Zsan impedance is reflected by the ratio squared
The usual traps
- Turns come whole: the voltage lands near, not on, what you asked.
- A real transformer also draws a magnetizing current and drops a few percent under load.
Questions
How do I calculate a transformer's turns ratio?
Vs / Vp = Ns / Np: volts follow the turns. Ip = Is × Ns / Np: amps go the other way. Zp = (Np / Ns)² × Zs: an impedance is reflected by the ratio squared.
What does it give for typical values?
19.2 : 1, 230 V → 12 V at 2 A. Turns ratio Np : Ns: 19.23 : 1; Secondary voltage: 12 V.
What are the usual mistakes?
Turns come whole: the voltage lands near, not on, what you asked. A real transformer also draws a magnetizing current and drops a few percent under load.
In the app
Your circuit, drawn live
Change a value: the schematic redraws with your numbers on the parts.
The part you can buy
Results rounded to standard values (E12, E24, E96) and power ratings.
The working, shown
Every step written out. Try it first by hand, then check.
Into your notebook
One click puts the circuit on a sheet of your project.
Open the calculatorOpens in the app on 1 December, with Circuit Notebook 1.0
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