The focus of this dissertation is to describe the electromagnetic modeling and optimization, mechanical modeling, thermal simulation and experimental characterization of two prototype permanent magnet-free high power density wound field synchronous machines (WFSMs) and one prototype of permanent magnet-wound field hybrid excitation synchronous machine (HESM) for electric and hybrid-electric vehicle traction applications. The WFSMs and HESM are designed for brushless rotor field excitation using an axial flux hydrodynamic capacitive power coupler (CPC) but can also be operated with a brush and slip rings excitation system. A flexible design environment has been developed for large scale multi-objective optimization of the machines, particularly focusing on the use of a static electro-magnetic solver, FEMM, and the extension of the software routines to reconstruct the transient behavior of rotating electrical machines.

The prototypes are designed to operate with a spray cooling system with automatic transmission fluid (ATF Dexron VI) in order to reach power densities comparable to the commercial permanent magnet synchronous machines (PMSMs) for similar applications. The spray cooling system was simulated with a commercial software (MotorCAD, (c)Motor Design Ltd 2018) and the modeling approach validated with experimental characterization. The spray cooling system was modified to include thermal circuit paths that emerged during the testing of the prototypes and integrated in the current release of the software.

The experimental characterization shows promising results, with peak output power at a base speed of 4,000 RPM exceeding 80 kW for the WFSM prototypes, and a continuous power output of 60 kW with the spray cooling system. The prototyped WFSMs achieve volumetric and specific torque and power densities of 17.22 Nm/l, 4.69 Nm/kg, 7.19 kW/l, and 1.95 kW/kg.

The experimental data collected for the HESM prototype shows a no-load rotor-side flux weakening capability that enables constant power speed ratio of 10:1 during operatio. The design of the HESM prototype was obtained with an integration of analytical sizing equations for the initial exploration of the design space and FEA methods for detailed modeling of the final prototype features.