Cooling of Automotive Traction Motors: Schemes, Examples, and Computation Methods

Abstract

This paper presents a comprehensive overview of the latest studies and analyses of the cooling technologies and computation methods for the automotive traction motors. Various cooling methods, including the natural, forced air, forced liquid and phase change types, are discussed with the pros and cons of each method being compared. The key factors for optimizing the heat transfer efficiency of each cooling system are highlighted here. Furthermore, the real life examples of these methods, applied in the latest automotive traction motor prototypes and products, have been set out and evaluated. Finally, the analytical and numerical techniques describing the nature and performance of different cooling schemes have been explained and addressed. This paper provides guidelines for selecting the appropriate cooling methods and estimating the performance of them in the early stages of their design. Index Terms-Automotive applications, cooling, traction motors, thermal analysis, numerical analysis. NOMENCLATURECross section area of heat path (m 2 ). , Linear current density (kA/m). , Inlet and outlet cross section areas (m 2 ). Specific heat capacity (J/kg). Diameter (m). , Friction loss factor (dimensionless). Gravitational attraction force (m/s 2 ). Grashof number (dimensionless). Fin extension (m). ℎHeat transfer coefficient (W/m 2 K). ℎLatent heat (kJ/kg). Loss coefficient (dimensionless).

Review of the Analytical Flow Model to Predict the Hydraulic Behaviour in Electrical Machine

“…The sudden expansion and contraction are divided into two main groups: the stationery and the rotational minor loss factors [4].…”

“…The minor loss factor for the contraction in the entrance of rotor axial ducts kr is calculated as [4], [10]:…”

“…In the air forced cooling method, this coefficient mainly depends on airflow speed. The airflow speed in the different sections of a throughventilated machine can be calculated by two different methods: analytical flow network analysis and numerical computational fluid dynamic (CFD) [4]. The hydraulic circuit method is the 1D analytical method which models the various flow paths of the machine [5].…”

“…The hydraulic circuit method is the 1D analytical method which models the various flow paths of the machine [5]. This method is the fast calculation method with acceptable accuracy [4]. However, the CFD method is the most precise method in flow speed calculation, but it has a high setup and computational time [4].…”

“…This method is the fast calculation method with acceptable accuracy [4]. However, the CFD method is the most precise method in flow speed calculation, but it has a high setup and computational time [4].…”