Hub motor

A hub motor puts the motor where the wheel is, so there is no chain, belt or gearbox at all. Most electric scooters in India, including the TVS iQube and Honda QC1, use one in the rear wheel.

• The stator, a ring of iron teeth wound with copper coils, is fixed to the axle, which is bolted to the swingarm and does not turn.
• Around it sits the rotor, a ring of permanent magnets fixed to the wheel hub. The rim and tyre are bolted to that hub, so the wheel is the rotating part of the motor.
• The motor controller takes DC from the battery and switches it into three phases, energising the coils in sequence so their magnetic field rotates.
• The magnets chase that rotating field, dragging the wheel round with them. Hall sensors in the stator tell the controller exactly where the magnets are, so it times each pulse correctly.
• Lift off and the same magnets passing the coils generate electricity instead, giving regenerative braking back into the battery.

Both brushless DC (BLDC) and permanent-magnet synchronous (PMSM) hub motors work this way; the difference is how the controller shapes the current. Power and sensor cables exit through the hollow axle.

What you notice: silent, direct drive with instant response and nothing to adjust or lubricate. The motor adds a few kilograms of unsprung weight to the wheel, which the suspension has to manage over potholes, and because there is no reduction gearing the motor must make its full torque directly, so it is larger and heavier than a geared mid-drive motor of the same power. Heat is also harder to shed from inside a wheel, which limits sustained hill climbing on cheaper designs.