Numerical Method Development for Cooling of End Windings of an Electric Motor

Abstract

This study focuses on bringing the CFD methodology for oil-cooling simulation of traction motors. With a tremendous rise in electric vehicles, it is desirable to check the capability of an electric motor at different operating conditions using CFD simulation. The thermal management of an electric motor is very essential as it directly impacts the design parameters and life of the electric motor. In this study, the CFD simulation has been carried out using Ansys fluent software to analyze the flow of oil inside a rotor shaft, the oil wetting area of the windings, and its effect on their temperature profile. Initially, the oil flow behavior in the hollow rotor shaft is studied using the pseudo-transient approach, and it is found that the flow distribution between the rear and front side nozzles is in the ratio of 0.91- 1.08. Additionally, transient simulation is conducted to capture the oil jet phenomenon on the end-space region, and the winding wetting area is computed. The total winding wetting percentage using the transient approach comes out to be 27%, which is 7% higher than that using the pseudo-transient method. Along with this, the mixed-time step coupling approach is used for extracting the contour of the temperature profile, which helps determine the temperature hotspot region of the motor components. This study is intended to reduce the computational time required for the transient simulation of motor cooling. Simulating complex motor geometry using a multiphase model with a moving mesh approach makes it a complex physics to simulate, eventually increasing the simulation time. The methodology used in this study can reduce the simulation time using some additional features of Ansys Fluent, like PUMA and NITA techniques. The methods used in this study will be implemented on the actual geometry with the hairpin windings to compare the time duration of this approach with the traditional approach.