Computationally Efficient Surrogate-Based Magneto-Fluid-Thermal Numerical Coupling Approach for a Water-Cooled IPM Traction Motor

Abstract

This paper proposes a computationally-efficient electromagnetic (EM)-computational fluid dynamics (CFD) coupling approach for a water-cooled Interior Permanent Magnet (IPM) motor. The numerical simulation of multiple fluids and their interaction with solid parts can be challenging. The proposed approach relies on the heat transfer coefficient (HTC) decomposition of different fluids/coolants inside the machine to generate an HTC look-up table (LUT) as a function of the coolant inlet flow rate. The HTC-LUT is then utilized as a surrogate model for the stationary coolant to decouple the fluid-to-fluid interaction and, hence, expedite the iterative approach. This reduces the computational time by almost twothirds as compared to the multiple fluid approach while preserving the fidelity of the model. Additionally, the proposed approach formulates the correlation between the rotor speed, coolant flow rate, convective heat transfer coefficients, and the temperature rise, particularly for hot-spot locations in the end-windings. This approach uses a two-dimensional EM model coupled with a three-dimensional fractional CFD model. Thus, it reduces the computational cost and retains the model simplicity. The viability of the proposed coupling approach is also validated through lumped parameter thermal network (LPTN) analytical approach. The results from both approaches under different cooling conditions, flow rates, and current densities are in a good agreement.INDEX TERMS Computational fluid dynamics (CFD), dual-three phase machine, finite-element analysis (FEA), hairpin windings, interior permanent magnet (IPM), synchronous machine, lumped-parameter thermal network (LPTN).

Rotor Fatigue Life Calculation Using Constant-Amplitude Load Cycles for an Interior Permanent Magnet Synchronous Motor

“…The thermal analysis is carried out using Motor-CAD, which uses an analytical approach to calculate the rotor temperature profile. Using a CFD simulation could help improve the accuracy of rotor temperature profile calculations [54]. Apart from the accurate S-N curve, multiple factors affect the fatigue life calculations, such as survival probability and surface roughness [11], [15].…”

Thermomechanical Rotor Fatigue of an Interior Permanent Magnet Synchronous Motor

“…As the temperature increases, the flux density of rare earth magnets decreases reversibly and, beyond a specific temperature, it may be demagnetized irreversibly [5]. Moreover, higher temperature leads to higher copper losses and may reduce the life expectancy of coils [6,7]. Therefore, ensuring a proper cooling mechanism for the IPMSM motor is critical to its performance.…”