Influence of the Wheel Rim Size on Different In-Wheel Motor Topologies

A comparison of in-wheel motors (IWMs) across different vehicle classes is difficult owing to considerable variations in size, power constraints, and the characteristics of IWM topologies. To address these issues, an objective comparison methodology for IWMs using the wheel rim as a mediator is proposed. First, the configurations of four typical IWM topologies with cooling systems are defined. Then, by analyzing the relation between wheel rim, tire, and vehicle, the standard wheel rim size is recognized as an important constraint for comparison. Moreover, four IWM topologies are optimized regarding torque volume density and duty-cycle efficiency across different rim sizes for selection of representative designs. Finally, the Pareto front designs of each topology and rim size are discussed electromagnetically and thermally via validated finite-element analysis. Results show that the wheel rim size considerably impacted the performance of IWMs. Energy consumption reduction is crucial for IWMs application in vehicles with rims up to 16 inches. For 18-inch-rim vehicles, double-rotor integral slot motor exceeds vehicle torque requirements along with energy consumption benefits, enabling further drivetrain configuration innovation. The 20-inch rims eliminate the difficulty of reducer installation which enhances torque density for inner-rotor fractional slot motors.