ANALYSIS AND DESIGN OF AN INERT-CORE MACHINE FOR VEHICULAR PROPULSION

There is a growing demand for lower-cost, lighter-weight, and more compact electric ma-
chines used for vehicle propulsion. In this research, a dual-rotor inert-core machine (ICM) is
considered to meet this demand. In the ICM, permanent-magnet-based Halbach arrays are
placed on inner and outer rotating structures. This enables one to eliminate magnetic steels
used in the stator and rotor of traditional electric machinery. In addition, a stator structure
that leverages a thermal plastic is proposed that facilitates straightforward active cooling
of phase windings, which greatly increases current density. To support the multi-objective
design of the ICM, a multi-physics toolbox has been developed. Within the toolbox, electro-
magnetic performance is predicted using a method-of-moments-based field solver. Thermal
performance is assessed using a thermal equivalent circuit that includes conductive heat
transfer from stator windings to the surrounding environment as well as convective heat
transfer to moving fluids. The structural integrity of the stator is assessed using analytical
expressions to predict stress from material properties, geometry, and applied external forces.
Calculated loss of proposed designs includes those of the stator windings as well as those
required for active cooling. Several optimization studies have been conducted to evaluate the
performance of the ICM under an expected electric vehicle driving cycle. From the studies,
Pareto-optimal fronts are obtained and used to explore the impact of alternative cooling
strategies on volumetric power density.