Radial-Flux Motor
Radial-flux motor describes a motor in which the main magnetic flux crosses the air gap in a radial direction, between a cylindrical rotor and stator.
What the term tells you
The term describes geometry, not how the rotor field is produced. A radial-flux machine may use permanent magnets, induction, electrical excitation, or reluctance torque. Most traction motors use this concentric arrangement because it packages naturally around a shaft and works with established winding, bearing, and manufacturing methods.
The contrasting geometry is an Axial-Flux Motor, where flux mainly crosses a disc-shaped air gap parallel to the shaft. Neither direction guarantees better efficiency or power density; diameter, length, cooling, materials, speed, and manufacturing limits determine the complete result.
For the detailed construction choices, see EV Motor Construction and Windings.