Designing a Modular ELV Motor Driver for High Current Sensor Less Motor Control

There is a trend in using an Extra Low Voltage of 48 volt for low power electrical vehicles. Although a lower voltage level is safer, the current level increases. Because of the higher starting currents in the low voltage system, the thermal design is very important. The current through the inverter can be be increased by reducing the thermal resistance between the mosfet and heatsink. In this paper an aluminum PCB is applied, to optimize the heat transfer from the mosfets to the heatsink. The inverter is build from three individual legs, and this design can be extended to multiple parallel legs, if the electric motor has multiple stator windings. The design of the PCB is discussed to achieve modularity, and a final three-phase inverter is constructed to test the maximum temperature on the Mosfets.