Electric motors for drones and eVTOL: how to compare them
Updated November 3, 2026
Almost every electric drone and eVTOL aircraft uses brushless permanent magnet synchronous motors (PMSM). They are efficient, power-dense and controlled entirely by electronics. What changes from one product to another is the topology, the voltage, the cooling and how much torque and power the motor can hold continuously.
Radial flux and axial flux
Radial flux
Axial flux
Shape
Long cylinder, rotor inside or outside the stator
Short, flat disc
Strength
Mature, robust, easy to manufacture and cool
High torque and specific power in a short length
Typical use
Multirotors, cruise propellers, geared drives
Direct-drive lift rotors, compact installations
Outrunner radial-flux motors dominate small and medium multirotors. Axial-flux machines are increasingly used where high torque is needed at low speed without a gearbox; see the axial-flux motors page.
Key specifications
Continuous power and peak power, with the peak duration. Hover and one-motor-inoperative cases often set the peak.
Continuous and peak torque, which matters more than power for large direct-drive rotors.
Kv (rpm per volt) for small motors, or the speed range at the rated voltage for large ones.
Mass and specific power (kW/kg). Check whether the mass includes the controller, cooling and mounting.
Efficiency at the cruise operating point, not only the peak efficiency.
Voltage class, from low-voltage motors for small drones to high-voltage machines for eVTOL.
Redundancy: some eVTOL motors have dual windings driven by two independent inverters.
Integrated motor-drives
Some manufacturers combine motor and inverter in a single unit, which removes high-current cabling between them and simplifies installation. Compare these with separate motor and ESC or inverter combinations on a like-for-like basis.
Kv is the motor speed constant: the no-load rpm per volt applied. A low-Kv motor turns slower and gives more torque per amp, which suits large propellers; a high-Kv motor suits small, fast propellers.
Is an axial-flux motor better than a radial-flux motor?
Not in general. Axial-flux motors give more torque in a short length, which suits direct-drive rotors. Radial-flux motors are mature, easy to cool and often lighter for high-speed applications. The right choice depends on the speed, torque and space of the installation.
Why do eVTOL motors use dual windings?
Two independent winding sets, each driven by its own inverter, let the motor keep producing reduced thrust if one channel fails. It is a common way to meet the safety objectives of piloted aircraft.
Should I compare continuous or peak power?
Both. Continuous power sizes the motor for cruise and long hover; peak power and its duration size it for take-off, climb and failure cases. A motor that only meets the requirement at peak power will overheat in service.
A literature-based review of how axial-flux permanent-magnet machines are sized for direct-drive lift rotors: hover torque requirement, torque-sizing relations, design and optimisation methods, reported parameter ranges, fault behaviour and regulatory context.
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