EV Dictionary: Electric Motors

An axial-flux motor routes magnetic flux along the shaft axis, creating a short, disc-shaped package.

Back-EMF is the voltage a spinning motor generates in opposition to the voltage driving it.

Cogging torque is position-dependent torque caused by rotor magnets interacting with stator teeth and slots.

How distributed, concentrated, and hairpin winding terms describe different motor choices.

Field weakening limits effective motor flux at high speed so back-EMF stays within inverter voltage.

FOC separates motor-current components so controllers can regulate torque and magnetic flux precisely.

An in-wheel motor places traction torque production at or inside a driven wheel.

An EV traction inverter converts battery DC into controlled motor current and manages regenerative power flow.

The motor air gap is the working clearance between the stator and rotor.

Permanent-magnet demagnetization reduces rotor flux reversibly or irreversibly under heat and opposing fields.

A permanent-magnet motor uses magnets to provide part or all of its magnetic field.

A PMSM uses rotor magnets that turn in step with the stator field to produce EV traction.

A radial-flux motor sends magnetic flux across a cylindrical air gap.

Reluctance motors use directional magnetic opposition to produce rotor torque.

The rotor is the rotating electromagnetic part that transfers motor torque to the shaft.

How the rotor cage and speed difference called slip produce induction-motor torque.

Rotor saliency is a directional difference in magnetic reluctance within the rotor.

Common-mode switching can create shaft voltage and bearing currents that threaten motor-bearing life.

The stator is the stationary active part that creates a motor's controlled magnetic field.

Torque ripple is the periodic variation of a motor's instantaneous torque around its requested level.

A WRSM or EESM uses electrically excited rotor windings instead of permanent magnets in an EV traction motor.