Method of rotor temperature prediction for an electric motor

A method for predicting a rotor temperature of an electric motor for an electric vehicle, comprising:

• measuring at least one operating parameter of the electric motor;
• inputting the at least one operating parameter of the electric motor into a predetermined regression model to predict a rotor temperature of the electric motor;
• and
• communicating a predicted rotor temperature of the electric motor to a control module for managing at least one thermal limits of the electric motor;
• wherein the at least one operating parameter of the electric motor comprises of a torque output, a rotor speed, and a stator temperature;
• wherein the at least one operating parameter of the electric motor further comprises a coolant flow rate;
• wherein the predetermined regression model is a mathematic relationship between a measured rotor temperature of a reference electric motor and at least one measured operating parameter of the reference electric motor including a torque output, a rotor speed, a stator temperature, and a coolant flow rate;
• and
• wherein the regression model is developed by a method comprising of:
• operating the reference electric motor at multiple predetermined rotor speeds;
• operating the reference electric motor at multiple predetermined torque levels at each of the multiple predetermined rotor speeds;
• measuring a rotor temperature and a stator temperature of the reference electric motor at each of the multiple predetermined torque levels at each of the multiple predetermined rotor speeds;
• measuring at least one of operating parameter of the reference electric motor at each of the at multiple predetermined torque levels at each of the multiple predetermined rotor speeds;
• and
• using regression analysis to develop a mathematic relationship between a difference in the measured rotor temperature and the measured stator temperature of the reference electric motor versus the at least one measured operating parameter of the reference electric motor.