Thermal management of electrically excited synchronous motor with integrated thermal network in automotive drive system

The trend toward vehicle electrification brings new opportunities and challenges for various types of electric machines, such as electrically excited synchronous motor (EESM). In EESM, rotor currents are required to create flux linkage. Adjustable rotor current adds a third degree of freedom to control the EESM. However, the rotor current also creates losses that can lead to critical temperatures. To take advantage of this degree of freedom and to balance the thermal states between the stator and the rotor, a new concept of EESM thermal management is presented in this paper, which aims to reduce the temperature increase during overheating. First, a low-order lumped-parameter thermal network (LPTN) is generated for temperature monitoring. Based on the thermal network, the control algorithm balances the temperatures of the stator and the rotor to slow down the temperature increase in the critical part. A simplified automotive drive system was built to simulate this control strategy. The SFTP-US06 drive cycle was used in the drive system to validate the control strategy.