Functional Integration of Power Electronics and Electric Machines Enabling High-Power Density Electric Drives

Integrated motor drives (IMDs), in which power electronics and electric machines are combined into a single assembly, are increasingly adopted in electrified transportation due to their advantages in shorter cabling, reduced cost, improved electromagnetic interference performance, and shared thermal management. However, most existing work is focused on increasing the power density of individual subsystems and physical integration. While these efforts can reduce the size of each component independently, they do not fully exploit the potential advantages of IMDs, where the motor and inverter can be co-designed. To overcome this, a paradigm shift is required in which integration is not only physical but also functional. This paper presents functionally integrated motor drives (FIMDs) as the next stage in electric motor and drive development and reviews existing technologies from three perspectives: magnetically integration, mechanically integration, and multi-functional integration. Within this framework, parts of the power electronics may intentionally participate in magnetic flux generation, energy buffering, structural support, or bearing. Furthermore, elements of the electric machine can assist in filtering, multilevel operation, mechanical component, or multi-functional component. This enables the removal or redistribution of bulky passive components such as the DC link capacitor, input inductors, split capacitors in multilevel inverters, external harmonic and electromagnetic filters, bearing, inductors in integration charging/discharging system, or even cooling channel.