Design of a 48 V three-phase inverter for automotive applications

Abstract

This project presents a design and construction of a three-phase inverter, drive circuit and dc-link capacitor bank. The inverter should be able to supply an electrical machine with 48 V and 250 A. Initial calculations and simulations were made to get some base for the ordering of hardware. The inverter board consists of six MOSFETs in parallel for each phase and the PCB itself is made of aluminum to enable a thermal substrate technique. The inverter PCBs are mounted on an aluminum frame where liquid runs between them to cool the inverter. The drive circuit is controlled with a dSPACE system and the tests are made with a load consisting of cables and iron powder cores. Temperatures are measured with PT100 sensors for the water and an infrared camera for the surfaces. Two different MOSFETs were investigated, one with higher switching losses and one with higher conduction losses. The two inverters were tested on an RL load and the cooling system picked up around 270 W at a phase current of 150 Arms. Theoretical calculations, performed with measured parameters, represents the temperature measurements well. The thermal resistance between the case and the sink in the inverter, Rcs, is measured to around 0:15 [K=W].