Propulsion System Design of Cadillac Lyriq Electric Vehicle

The design and development of EVs and HEVs has become a growing issue recently due to concerns about pollution and dependence on non-renewable fossil fuels. Accordingly, General Motors (GM) has an evolving vehicle electrification plan over the past several decades and into the future to deliver low-cost and efficient EVs. The propulsion system of GM-Cadillac's first electric vehicle, the Lyriq, is designed to deliver significant improvements in both range and peak performance. Its propulsion system uses an optimized drive unit consisting of interior permanent magnet (IPM) motors and silicon traction inverters. The main objective of the drive unit design was to minimize energy loss and cost while maximizing hardware consolidation, range, performance, power density and scalability. Two IPM motors are designed with different stack lengths and number of stator turns, while keeping the rotor design and stator conductor profiles the same. The larger motor is used in rear-wheel drive (RWD) applications, while both motors are used in all-wheel drive (AWD) applications. A high-speed rotor is designed to achieve higher power density. The AC winding effect at higher speeds is mitigated by using a much smaller cross-section bar conductor. The rotor surface has a special notched design to minimize acoustic noise without the use of rotor or stator skew. In addition, the traction inverters in the Lyriq EV are designed with a strong emphasis on scalability and adaptability to different vehicle architectures, taking into account a wide range of requirements. This paper discusses various design, development and testing aspects of the propulsion drive unit used in the Cadillac Lyriq vehicle.