Generator Coil Input Form
Example Data Table
| Build Type | RPM | Poles | Coils | Turns | Wire | Use Case |
|---|---|---|---|---|---|---|
| Small wind alternator | 250 | 16 | 12 | 90 | 1.0 mm | Battery charging |
| Pedal generator | 450 | 12 | 9 | 65 | 1.3 mm | Low voltage DC |
| Hydro wheel unit | 320 | 20 | 15 | 70 | 1.5 mm | Continuous output |
Formula Used
Frequency: f = RPM × poles ÷ 120
Flux per pole: Φ = B × magnet area × flux factor
RMS voltage per coil: E = 4.44 × f × N × Φ × winding factor
Phase voltage: Vphase = E × coils per phase
Star line voltage: Vline = Vphase × √3
Delta line voltage: Vline = Vphase
Wire resistance: R = ρ × length ÷ wire area
Temperature correction: ρT = ρ20 × [1 + 0.00393 × (T - 20)]
Copper loss: Ploss = phases × current² × phase resistance
Output power estimate: Pout = phases × loaded phase voltage × phase current × power factor
How to Use This Calculator
Enter the rotor speed, total magnet poles, coil count, and phase count.
Add your expected turns per coil, magnet face area, and flux density.
Use the flux factor to adjust for air gap and leakage.
Enter wire diameter and average turn length to estimate resistance.
Set the expected phase current to check voltage drop and copper loss.
Press the calculate button. The result appears below the header and above the form.
Use the CSV and PDF buttons to save your design estimate.
Axial Flux Coil Planning
Why Coil Design Matters
Axial flux generators use flat rotors and flat stator coils. The magnetic field moves across each coil face. This shape can give strong torque at low speed. It is popular in wind turbines, hydro wheels, and compact alternators.
Flux, Turns, and Voltage
A coil design starts with flux. Flux depends on magnet strength and magnet face area. It also depends on air gap, steel backing, and leakage. This calculator uses flux density, magnet area, and a flux factor. The factor lets you reduce the ideal value when the build has wider gaps or weaker coupling.
Turns are the next key choice. More turns raise voltage at the same speed. They also add wire length and resistance. Resistance causes heat and voltage drop under load. A useful coil is therefore a balance. It must reach the needed voltage without wasting too much power.
Wire and Winding Space
Wire diameter affects current capacity. Thicker wire lowers resistance. It also fills the coil window faster. Thin wire allows more turns, but it heats sooner. The fill factor helps you judge whether the winding is realistic. A neat hand wound coil may have lower fill than a machine wound coil.
Frequency comes from rotor speed and pole count. More magnets create more electrical cycles per turn. A higher frequency raises induced voltage for the same turns. It can also increase losses in iron parts, if a cored stator is used. Air core stators avoid much of that loss.
Practical Design Use
The calculator estimates coil voltage using the common transformer style equation. It uses RMS voltage for a sinusoidal waveform. Real axial machines can produce different wave shapes. Magnet shape, coil shape, and spacing all matter. Treat the result as a design estimate, not a final lab test.
Use the output table to compare options. Try one change at a time. Raise turns, then review voltage and resistance. Increase wire diameter, then check heat loss. Adjust the flux factor when your air gap changes.
Good builds need careful testing. Measure open circuit voltage first. Then add a safe load. Watch coil temperature. Check rectifier heating. Record rpm during every test. These steps turn the calculated plan into a reliable generator design.
Keep notes so later winding revisions become easier and safer.
FAQs
1. What is an axial flux generator coil?
It is a flat wound coil placed in the stator of an axial flux generator. Magnets pass across the coil face and induce voltage.
2. Why does pole count affect voltage?
More poles create more magnetic cycles per rotor revolution. This raises frequency, which raises induced voltage when other inputs stay unchanged.
3. What does the flux factor mean?
It reduces ideal magnetic flux for air gap, leakage, spacing, and construction losses. Use a lower value when coupling is weak.
4. Should I use star or delta connection?
Star gives higher line voltage from the same phase voltage. Delta gives higher current capability, but line voltage equals phase voltage.
5. Why is wire resistance important?
Resistance causes voltage drop and heat under load. High resistance can waste power and make coils run too hot.
6. Is the voltage result exact?
No. It is an estimate. Real voltage depends on magnet shape, coil shape, air gap, waveform, temperature, and build accuracy.
7. What fill factor should I enter?
Hand wound coils often use 0.45 to 0.60. Very neat winding can be higher. Insulation and spacing reduce the usable area.
8. How can I reduce copper loss?
Use thicker wire, shorter turns, fewer series coils, or lower current. Always check whether the new winding still reaches target voltage.