Identification of design rules for interior PM motors with different cooling systems

Abstract

The conventional scaling rules for the optimal design of electric machines are best suited for naturally cooled machines with stator winding current densities less than 4A/mm 2 . In this paper, through a comprehensive sensitivity analysis, first, it is demonstrated that the correlations between some geometric variables and the performance metrics of interior permanent magnet (IPM) motors vary significantly with respect to the stator winding current density. For this purpose, three current densities are selected so as to approximately account for naturally cooled, fan-cooled and liquid-cooled machines. Subsequently, a parameterized IPM motor is optimized at these current densities through a large-scale design optimization algorithm by evaluating a total of 20,000 design candidates. The 100 best designs from each group are then identified and extracted to investigate the scaling rules for the optimal design of such IPM motors with different cooling systems. The outcomes of the study are in correspondence with the conventional design principles for naturally cooled machines. Nevertheless, it is illustrated that these rules vary for fan-cooled and liquid-cooled machines owing to the increased ampere loading, and also heavy saturation of the magnetic core in such machines. A configuration of a 50 hp, 48-slot, 8-pole IPM motor with a single-layer v-type magnet is used as the benchmark of this study.Index Terms-Machine modelling and general design, computer aided design, permanent magnet machines, finite-element analysis, sensitivity analysis, design of experiments, design optimization.

Large-scale electromagnetic design optimization of PM machines over a target operating cycle

“…A case of particular concern pointed out by numerous studies [8][9][10][11] is in traction applications, where the motor is most likely to operate far away from its rated torque and nominal speed. This is whereas the correlation between the main design variables and motor performance metrics, can be significantly affected by the machine's level of ampere loading and magnetic core saturation [12]. This accentuates the challenges in the design of electric motors with intermittent operating cycles where an optimal design is to maintain high performance under various loading conditions.…”

Optimal Design of IPM Motors With Different Cooling Systems and Winding Configurations

“…This paper contains further contribution through a parallel investigation of the relations between the geometric design parameters and the performance metrics of interior PM (IPM) motors for a wide range of ampere-loading levels determined by the machine's cooling system. 20 This is accomplished through a systematic sensitivity analysis and large scale design optimization. Accordingly, it will be demonstrated that one set of design rules, such as those derived in, 19 cannot be generalized to all three classes of cooling systems.…”