Free deterministic sizing tool
Enter RPM, cooling, and DC bus voltage to screen whether a 100mm axial flux generator can meet your power, torque, current, and package limits before you request a custom winding design.
Diameter
100 mm
Cooling modes
Air / liquid
Bus targets
24-96 V
Reviewed
July 23, 2026
Decision summary
The active radius is small, so continuous torque is the first feasibility limit. Air-cooled planning points should stay near 1.8 Nm; liquid cooling can screen up to about 3.5 Nm before detailed thermal work.
Evidence: Calculator assumptions reviewed July 23, 2026.
The same mechanical power can be impractical at a low DC bus voltage because rectifier, cable, and connector current rise quickly. The tool therefore estimates current, not only shaft output.
Evidence: DC current uses output watts divided by bus voltage and 92% conversion efficiency.
Above 8,000 RPM, tip speed, eddy-current loss, balance, and magnet retention risks become more important than the headline power number.
Evidence: Boundary state uses a 100mm outside-diameter tip-speed check.
Method and limits
The calculator is deterministic: the same inputs return the same output. Values are intentionally framed as planning screens because thermal, winding, rectifier, and rotor validation decide the final datasheet.
| Variable | Formula or value | Use | Limitation |
|---|---|---|---|
| Shaft power | kW = Nm x RPM / 9549 | Converts the continuous torque screen into usable generator output. | Does not replace dyno or thermal validation. |
| Cooling torque limit | Air: 1.8 Nm; liquid: 3.5 Nm | Separates compact natural cooling from water-jacket planning points. | Actual value depends on winding fill, housing, airflow, and duty cycle. |
| High-speed derating | Torque derates above 6,000 RPM to a 70% floor | Prevents high-RPM power from looking unrealistically linear. | Exact loss curve requires electromagnetic and thermal simulation. |
| Rectified DC current | A = output W / (bus V x 0.92) | Screens rectifier, cable, connector, and controller-current pressure. | Winding voltage constant and rectifier topology still need design work. |
| Tip speed | m/s = RPM x pi x 0.1 / 60 | Flags rotor-retention and balance risk for the 100mm envelope. | Rotor material, sleeve, adhesive, and magnet geometry are not modeled. |
Use-case fit
| Application | Useful input | Likely fit | Next action |
|---|---|---|---|
| Small wind or VAWT generator | 100-1,000 RPM, 24-48 V | Possible only with low-speed winding and startup review | Confirm cut-in RPM, rectifier threshold, and cogging target. |
| Drone or mobile auxiliary power | 3,000-8,000 RPM, 48-96 V | Strong when high RPM is available and mass is constrained | Send duty cycle, cooling airflow, and battery bus limits. |
| Compact engine or belt-driven alternator | 2,000-6,000 RPM, 48-96 V | Good first-pass fit if shaft load and vibration are controlled | Validate bearing loads, mounting flatness, and rectifier cooling. |
| Micro hydro direct drive | 100-800 RPM, 24-72 V | Usually needs larger diameter unless gearing is acceptable | Compare turbine speed curve against low-RPM output. |
Related engineering paths
Use these internal references to move from the estimate to a product family, application boundary, validation gate, or RFQ.
Calculate sizing and limits for low-speed 100 RPM generators.
Screen voltage, speed, current, and thermal limits for a motor request.
Review direct-drive generator program scope and customization paths.
Map wind and hydro speed ranges to generator sizing constraints.
Understand topology tradeoffs before choosing axial or radial flux.
Use dyno, thermal, vibration, and inspection checks before production.
Share RPM, voltage, duty cycle, package length, cooling, and quantity.
FAQ
It can screen near or above 1 kW at high RPM with liquid cooling, but continuous rating depends on winding temperature, rectifier losses, and housing heat rejection.
Voltage determines current for the same output power. A low-voltage target can make wiring and rectifier heat impractical even when the mechanical output looks possible.
Enter the generator shaft speed after any pulley, gearbox, turbine, or engine coupling. Do not enter motor no-load speed or expected electrical frequency.
A 100mm rotor at high RPM needs magnet retention, rotor balance, bearing, and iron-loss validation. The calculator derates torque, then flags the point for engineering review.
At very low speed, startup torque, cogging, winding resistance, and rectifier voltage drop decide whether useful power is available.
It uses a 92% rectifier/conversion assumption for current and discloses the limitation. A final design still needs a measured efficiency map.
Send the copied calculator result plus application, peak and continuous duty cycle, available axial length, cooling method, voltage/current limits, and prototype quantity.
Some electromagnetic design choices overlap, but winding, inverter, thermal duty, sensor plan, and validation targets should be reviewed separately for motor operation.
No. It is a deterministic feasibility screen intended to decide whether a custom 100mm generator is worth detailed electromagnetic, thermal, and mechanical design.
Next step
The fastest path to a useful engineering reply is to copy the result, then include peak and continuous time windows, cooling method, package length, rectifier or battery voltage, and sample quantity. Unknown values can be marked N/A.
Inquiry Email
Please include application, peak/continuous torque, speed range, voltage/current limit, outer diameter, axial length, cooling method, quantity, and drawings or reference samples.
Instant Chat
+86 188 5797 1991
Share torque-speed, package, cooling, and sample quantity in the first message.
