This paper is mainly about heat dissipation and improvement technology, aiming at solving the problem that the driving motor of 4 low-speed electric vehicles has too high a rising speed when running under complicated working conditions. Core losses and conductor losses are calculated by using the finite element method as well as known empirical formulas, and magnetic eddy loss at three operating conditions (normal condition, maximum speed, and peak torque. The computed heat loads are then used to establish the complete 3- dimensional model of thermal analysis.
As shown in Figure 3, without active cooling, the hottest conductors would be at about 141°C (Class-B Insulation limit). Therefore, three different liquid cooling designs (helical channel, serpent channel, and annular flow) have been designed and analyzed. A coupled thermal- fluid simulation has been performed on the helix structure, which showed better results, so we selected it to be optimized.
The optimization is performed using central composite design, genetic algorithms for response surfaces, and multi-objective evolutionary optimization (NSGA-II). The objective function is to simultaneously achieve a low maximum working temperature as well as good heat transfer properties by changing the geometry of cooling channels.
The cooling of the motor as well as the suction pressure was optimized, after which a decrease by up to 31.1°C (up 8.6% on the maximum temperature) was observed. Also, pressure drop reduction as much as 23% along with substantial increases in both the heat transfer performance and reliability.