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Size your EV motor in 60 seconds.
Pick a vehicle. See four motor types side by side, then download a build sheet for your workshop.
- 4 motor types NdFeB, ferrite, induction, axial flux
- Real driving WLTC, India MIDC and IDC, or your own GPS route
- Build sheet PDF winding, controller, cables, battery pack, cost
Choose your vehicle
Every number can be changed afterwards on the Specs tab.
Sample project (fictional): CNG auto-rickshaw (three-wheeler) · Pro compares your own vehicle
Versus your current vehicleCNG vehicle → Ferrite spoke, IDC cycle
Fuel figures are tailpipe only; electricity CO₂ uses the grid factor you entered. Conversion cost is the full parts list on the Build tab (Ferrite spoke).
At a glance
Four motor types, same vehicle
Motor + inverter loss at constant speed
Level road, no wind. Cruise loss sets highway range.
Your motor, drawn to its size
Cross-section and side view are scaled from the calculated active diameter and length. Illustrative layouts of textbook motor types; the axial-flux view shows the rotor disc face.
3D assembly Ultra preview
Sample projects from fictional customers, shown as Ultra builds them. Rotate, explode and cut through them. With Ultra, the 3D model is built from your own motor and every value can be changed.
Values to play with
Parts tap to select, untick to hide
Masses from the 3D geometry
Side by side, to scale
Same vehicle, four technologies, plus your size if you entered one. Diameter shown true to scale.
Build sheet Pro
Winding, controller, wiring, gearing, battery pack and parts list for one motor, ready to take to a workshop or supplier.
Sample project (fictional): CNG auto-rickshaw (three-wheeler) converted to a ferrite spoke motor.
With Pro, this sheet is calculated for your own vehicle and motor, with 2 PDF downloads a month. Ultra raises this to 20 PDFs a month and adds your logo and supplier searches.
Join the waitlistWinding8 poles · 48 slots · 3 phases
- Winding type
- Distributed, double layer, 5/6 pitch
- Turns per phase (series)
- 18.0
- Parallel paths
- 8
- Conductors per slot
- 18
- Conductor
- 2 strands × Ø1.00 mm (1.5 mm²)
- Current density (continuous)
- 6.5 A/mm²
- Slot fill, bare copper
- 31%
- Back-EMF constant
- 7.3 V rms line / 1000 rpm
- Torque constant (peak)
- 0.23 Nm / A rms
- Electrical frequency, max
- 400 Hz
- Copper skin depth at max
- 3.30 mm
ControllerMOSFET (100–150 V class)
- DC bus
- 72 V
- Phase current, peak
- 241 A rms (341 A peak)
- Phase current, continuous
- 80 A rms
- Rating to buy (15% margin)
- 277 A rms peak
- Switching frequency, at least
- 8 kHz
- Power, peak / continuous
- 11.7 / 3.9 kW
DC side and cablescopper, 90–125 °C insulation
- Battery current, peak
- 184 A
- Battery current, continuous
- 61 A
- Main fuse
- 150 A, rated ≥ 90 V DC
- DC cable (+ and −)
- 25 mm²
- Phase cables (×3)
- 25 mm²
- Main contactor
- yes, with precharge (72 V)
Gear and climbingtwo stages
- Reduction ratio
- 9.87 : 1
- Wheel torque, peak
- 535 Nm
- Max wheel speed
- 608 rpm
- Steepest hill start (grip or torque)
- 38%
- Sustained climb at 20 km/h
- 9.8%
Battery packLFP · 230 cells
- Configuration
- 23s 10p
- Energy
- 11.0 kWh (asked 10.0)
- Voltage range
- 58–84 V (nominal 74 V)
- Continuous current, cells
- 450 A
- Peak C-rate needed
- 1.2 C
- Pack mass, estimate
- 102 kg
Parts list and cost10–50 k units/yr · USD
| Electrical steel | 7.3 kg | $33 |
| Copper (winding) | 1.7 kg | $22 |
| Ferrite magnets | 0.53 kg | $4 |
| Housing, shaft, bearings, assembly | $150 | |
| Motor controller (inverter) | 277 A rms | $110 |
| Reduction gear, two stages | 9.87 : 1 | $57 |
| Battery pack | 23s10p, 11.0 kWh | $1,290 |
| Cables, fuse, contactor | 25 / 25 mm² | $140 |
| Total, drive system and pack | $1,804 |
Supplier links Ultra preview search marketplaces with this exact specification. Costs above are volume estimates; single-piece prices are higher. We do not endorse any seller.
Checks
Slot fill 31% is buildable with round wire (up to about 45%).
Cells can supply the peak current (184 A vs 450 A continuous rating).
How it is calculated
Method details below are in English.
The reduction ratio is chosen so the motor reaches top speed at maximum rpm. Peak power is the smallest value that meets the acceleration target (limited by tyre grip) and the road load at top speed. The constant-torque region ends at one third of maximum speed.
- Rotor volume comes from a type-specific air-gap shear stress (liquid cooled: NdFeB 85, ferrite spoke 70, induction 55 kPa; air cooling ×0.65). Stack length is 0.75 × rotor diameter.
- Axial flux: yokeless, segmented-armature stator between two magnet discs (two air gaps, inner/outer radius 0.6, 50 kPa per gap when liquid cooled). Rotor rim speed is capped at 100 m/s, which lowers its maximum rpm (published axial motors run at about 60–110 m/s). Axial length is 0.32 × diameter. Its manufacturing cost carries a 30% premium (segmented stator, two rotors, axial bearings). Motor mass follows 0.45 × T0.645 kg, fitted to EMRAX 188/228/268 and YASA 400/750 datasheets (within ±17%).
- Your own axial motor: torque also grows with the axial length available for coils and magnets. About 0.32 × diameter is typical; shorter motors lose torque, and beyond about half the diameter extra length adds little.
- Your own motor: the same shear stress turns your diameter and length into peak torque; peak power is that torque at base speed. Usable power is capped by the battery (4C) and by a 900 A automotive inverter. Acceleration and top speed are simulated with the usable power.
- Rotor rim speed is capped (NdFeB IPM 170, ferrite spoke 100, induction 160, axial disc 100 m/s), which lowers the maximum rpm of large rotors.
- Constant-power speed range is 3 : 1, but 2.2 : 1 for ferrite spoke (its weaker magnet flux limits field weakening), so a ferrite motor holds its peak torque up to a higher base speed.
- Build sheet: turns per phase come from the flux linkage needed at base speed with space-vector modulation and an average loaded air-gap flux density; whole conductors per slot are chosen with parallel paths. Strand size respects copper skin depth at maximum frequency. Cables at 5 A/mm² continuous, fuse at 1.25× continuous battery current, pack from series/parallel cells.
- Inverter current follows from peak power, bus voltage and a type-specific power factor.
- Losses (copper, iron, magnetising, mechanical, inverter) are summed second by second over the chosen drive cycle, clipped at top speed: WLTC class 3, MIDC (India: four urban cycles plus an extra-urban cycle capped at 90 km/h, 1,180 s, 10.6 km) or IDC (India 2- and 3-wheelers: six 108 s cycles, 3.95 km, max 42 km/h), built from the ARAI operation tables. Your own GPX or CSV route is resampled to one second; road grade from elevation adds climbing and regeneration. Auxiliary load 300 W, gearbox efficiency 97%.
- Costs are for 10–50 k units per year and use the material prices you enter. Fixed parts (housing, bearings, assembly, controller base cost) scale down for small machines; controllers at or below 100 V use a lower cost per amp.
Coefficients are published averages, cross-checked against our own field simulations. Results are for early concept sizing and do not replace detailed electromagnetic design or testing.