Development of High Power 48V Powertrain Components for Mild Hybrid Light Duty Vehicle Applications

In this paper the development of a high power (20-25kW) 48V electric machine designed to fit into a dual clutch transmission (DCT), and a corresponding inverter are reported. The electric machine was a frameless 6-phase, 8-pole, interior permanent magnet (IPM) motor with oil (automatic transmission fluid, ATF) cooling and novel windings, and the inverter was a compact oil cooled silicon MOSFET design. Both were designed, built and tested. The motor was designed to fit into the same volume as an existing 15kW machine to enable testing in the existing gearbox, whereas the inverter was designed as a standalone unit. A major aim of the design was to make it possible to cool the motor, inverter and gearbox from the same oil supply. In this paper the benefits of running such 48V systems at powers higher than 10-15kW is discussed along with some of the design challenges encountered and the ways that they were addressed.