Use of Thermally Conductive Electrically Insulative (TCEI) Materials in E-Motor Slot Liner Applications

Slot liners are commonly used in electric motors to electrically insulate the motor windings from the laminated core. However, thermal conductivity of materials commonly used as slot liners is very low compared to other components in the motor thus creating a barrier for heat transfer. This thermal barrier affects overall motor performance and efficiency. Also, slot liners typically lack intimate contact with the laminated core resulting in air gaps which further increase thermal resistance in the system.

Slot liners are traditionally made from high temperature films/papers that are cut and slid into slots of motors. The current work proposes developing an injection moldable slot liner to minimize air gaps. Additionally, use of TCEI materials further lowers thermal resistance. A thermal finite element model has been developed to evaluate effects of slot liner thermal properties and air gaps on temperature distribution within the motor. The model incorporates varying material orientation of components within the motor and uses temperature dependent orthotropic material properties for the analysis. Air gaps are modeled using an equivalent thermal conductivity approach to capture effective thermal resistance for various airgap thicknesses. Results indicate that increasing thermal conductivity of the slot liner material and minimizing air gaps significantly reduces maximum temperatures within the motor.