In this study, electrical machine technologies are compared comprehensively for a hybrid turbocharger used with a high-power marine engine. It is required for the machine to operate in a thermally aggressive environment, with turbine exhaust temperatures in excess of 600°C. Furthermore, it is required to both generate from the extra exhaust energy (turbo-compounding) at high-engine loads as well as a motor for low-engine loads during slow steaming. The application investigated translates to a machine featuring both high-power (150 kW) and high speeds (25–50 krpm), together with a considerable constant power–speed region. In this study, induction machines (IM), permanent magnet machines and switched reluctance machines are compared taking into account a number of aspects including the thermal performance, torque ripple, converter volt–ampere rating, and cost. In light of the technical and market requirements, the IM featuring new materials is prototyped and tested for the application in a representative environment.