Three currents from the inverter make a magnetic field that runs round the stator; the rotor's magnets are pulled along with it, and two gear stages turn that into wheel torque. Move across the figure to press the pedal; move to the far left to lift off and regenerate.
Fig 1Electric drive unitHover or ← → to set the pedalstopped · 0 rpm
Rotor: six poles of V-shaped magnets, turning with the fieldPhase APhase BPhase C: coil ends glow with their currentGear window: 16→49, then 21→62 to the differential, 9.04 : 1A Model 3-class rear drive unit with the motor's end cover off. The inverter turns the pack's 350 V DC into three sine currents 120° apart; in the 54 slots they make a magnetic field that turns at the rotor's own speed, so the motor is synchronous: 3 pole pairs means the currents cycle three times per revolution (900 Hz at 18,000 rpm). Pressing the pedal makes the inverter lead the field ahead of the rotor's magnets (lit teeth), and the magnets and the rotor's reluctance pull it round; lift off and the field drops behind, the motor becomes a generator and current flows back into the pack (regenerative braking). Two gear stages cut the speed by 9.04 before the differential, so the wheels turn nine times slower with nine times the torque. The drawing turns 300 times slower than the real shaft; the readout, the needle and the current are live from a simple vehicle model (1.9 t, 375 Nm, 208 kW, 235/45 R18).