Multi-Objective Optimization of Permanent Magnet Synchronous Motor for Electric Vehicle Considering Demagnetization

Abstract

The irreversible demagnetization of permanent magnets causes the deterioration of the performance in permanent magnet synchronous motors (PMSMs), which are used for electric vehicles. NdFeB, which is the permanent magnet most commonly used in PMSMs for electric vehicles, is easily demagnetized at high temperatures. Because traction motors for electric vehicles reach high temperatures, and a high current can be instantaneously applied, permanent magnets of PMSM can be easily demagnetized. Therefore, it is important to study the demagnetization phenomenon of PMSMs for electric vehicles. However, since the demagnetization analysis procedure is complicated, previous studies have not been able to perform optimization considering demagnetization characteristics. In this study, we optimized the shape of a PMSM for electric vehicles by considering the demagnetization characteristics of permanent magnets using an automated design of experiments procedure. Using this procedure, a finite element analysis for each experimental point determined by a sampling method can be performed quickly and easily. The multi-objective function minimizes the demagnetization rate and maximizes the average torque, and the constraints are the efficiency and torque ripple. Various metamodels were generated for each of the multi-objective functions and constraints, and the metamodels with the best prediction performance were selected. By applying a multi-objective genetic algorithm, 1902 various optimal solutions were obtained. When the weight rate of the demagnetization rate to the torque was set to 0.1:0.9, the demagnetization rate and average torque were improved by 4.45% and 2.7%, respectively, compared to those of the initial model. The proposed multi-objective optimization method can guide the design of PMSMs for electric vehicles with high reliability and strong demagnetization characteristics.

Investigation of Six-Phase Surface Permanent Magnet Machine With Typical Slot/Pole Combinations for Integrated Onboard Chargers Through Methodical Design Optimization

“…Figs. 23 and 24 show the dynamic response of the prototype machine during propulsion mode. It is clear that the employed controller can efficiently respond to the speed change from 0 to 1000 rpm.…”

“…Performance-wise, the main criteria when designing an SPM machine for the integrated charging process of EVsbesides the developed torque and core lossesare radial forces, irreversible demagnetization, and cost [22][23][24][25]. Even though considerable design optimization work has been reported in the literature, a concept satisfying all the above-mentioned objectives has not been conceived so far.…”

“…Another crucial aspect when designing the PMSM is the irreversible demagnetization, which yields the deterioration in the performance of the motors [27,28]. Rareearth NdFeB magnets are well-known for their high residual magnetic flux density and coercivity; albeit, these magnets can be easily demagnetized at high temperatures [23]. Therefore, Ref.…”

“…Therefore, Ref. [23] presented the design optimization of PMSM considering the demagnetization characteristics. In that case, minimum demagnetization rate and maximum average torque constitute the objectives of the optimization problem, while the constraints are the peak-to-peak torque ripple and efficiency.…”

Minimization of the Electromagnetic Torque Ripple of a Synchronous Reluctance Generator Using External Rotor Excitation

“…The main disadvantages of using permanent magnets, such as irreversible demagnetization, which causes poor performance in this machine, are detailed in Multi-Objective Optimization of Permanent Magnet Synchronous Motor for Electric Vehicle Considering Demagnetization [7]. In addition, Detection of Eccentricity Faults in Five Phase Ferrite PM Assisted Synchronous Reluctance Machines [8] discusses the failures due to eccentricities in the rotor with inserted permanent magnets, leading to the generation of mechanical stress and electromagnetic asymmetries, which worsens the machine performance.…”