Hollow Shaft Liquid Cooling Method for Performance Improvement of
Permanent Magnet Synchronous Motors Used in Electric Vehicles 2023-01-5067
Operating condition of rotor embedded magnet materials for permanent magnet
synchronous motor (PMSM) critically affect electric vehicle (EV) range and
dynamic characteristics. The rotor liquid cooling technique has a deep influence
on PMSM performance improvement, and begin to be studied and applied
increasingly in EV field. Here, the fluid, thermal, and electromagnetic
characteristics of motor with and without hollow-shaft cooling are researched
comprehensively based on 100 kW PMSM with housing water jacket (HWJ) and
hollow-shaft rotor water jacket (SWJ). The solid models are constructed
considering temperature-dependent power loss and anisotropic thermal
conductivity. After the fluid models are set up by using Reynolds stress model
(RSM), conjugate heat transfer is conducted through computational fluid dynamics
(CFD) simulation, and is verified by real PMSM test bench experiments. The
thermal-electromagnetic coupled analyses are carried out via finite element
methods (FEM) taking into account the temperature-dependent magnet operating
point. Compared to HWJ-alone cooling at the motor rated condition, the winding
temperature with SWJ cooling has 20°C lowers, and 70°C lowers in magnet
position, as well as the motor output power is improved by 3% to 4%. This
cooling method will provide a great helpness on motor’s power density, module
lightweighting, and system economy.