Dong-Kuk Lim

Analysis and Design of a Multi-Layered and Multi-Segmented Interior Permanent Magnet Motor by Using an Analytic Method

Although demand for the multi-segmented and multi-layered (MSML) interior permanent magnet (IPM) motor is high, the analytic method for this motor has not yet been proposed. The finite element method has been used in the analysis and design of the MSML IPM motor, even though it takes much time to perform. To solve this problem, the correct and rapid analytic analysis method for the MSML IPM motor is proposed in this paper. This method is called the MCC method because it is the combination of the Magnetic equivalent circuit, Conformal mapping to consider slotting effect, and Concentration flux of IPM. Furthermore, the feasibility of the optimization of the MSML motor by using the proposed MCC method is verified in this paper.

Cogging Torque Minimization of a Dual-Type Axial-Flux Permanent Magnet Motor Using a Novel Optimization Algorithm

The design of an electric machine is a multivariable and multimodal problem that requires much time to find the optimal design result. To address this problem, we propose a novel optimization algorithm using a kriging meta-model, a contour face climb method, a reinterpolation method in an expected region, an advanced pattern search method, and a uniform search method in the entire problem space. A rapid, exact, and reliable optimization process for a multivariable and multimodal design problem is possible using the proposed novel algorithm. Its validity was confirmed by comparing the optimization results of a test function with evolutionary optimization methods. For verification of the application to an electric machine, a dual-rotor axial flux permanent-magnet synchronous motor was designed using the proposed algorithm in this paper.

A 2-D Finite-Element Analysis for a Permanent Magnet Synchronous Motor Taking an Overhang Effect Into Consideration

In the two-dimensional (2-D) finite-element (FE) analysis, the overhang effect can be considered through an increase in the remanence flux density of the permanent magnet in order to reflect the increment of the air-gap flux density due to the overhang structure. However, a repetitive 2-D FE analysis was performed in order to match the air-gap flux density with it in the three-dimensional (3-D) FE analysis. The proposed method accurately accounts for the overhang effect without trial and error. From the results of the 3-D FE analysis, the validity of the proposed method is verified.

Magnetic Equivalent Circuit Model Considering Overhang Structure of a Surface-Mounted Permanent-Magnet Motor

An overhang structure is used to enhance the air-gap flux density and increase the torque density of a motor. In the preliminary design stage, consideration of the overhang effect is important for a precise prediction of the performance of a motor with overhang and for the selection of the proper overhang length. The 3-D finite-element method (FEM) is essential when analyzing a motor with an overhang structure due to the asymmetry in the axial direction caused by overhang. However, it is computationally expensive and time-consuming, especially during the initial design stage. In this paper, we propose a magnetic equivalent circuit model, which considers the overhang structure of a surface-mounted permanent-magnet motor. With the proposed analytical method, the computational time is significantly reduced in the preliminary design stage. The proposed analytical model is verified with a 3-D FEM analysis.

Cogging Torque Optimization of Axial Flux Permanent Magnet Motor

The conventional climb method is difficult to apply for the multimodal and multi-dimensional optimization problem. To solve this problem, the improved climb method is proposed in this paper. The proposed algorithm can mitigate the time for the optimization and increase the reliability for the optimization. The proposed algorithm is verified through the optimization of an axial flux permanent magnet motor.

Characteristic Analysis and Design of a Thomson Coil Actuator Using an Analytic Method and a Numerical Method

The Thomson coil actuator (TCA) is a useful switch due to its simple structure and rapid completion time. However, research on the TCA is not widely available. Research on the TCA has been focused on the basic working principles and the characteristic analysis of the TCA. To address these problems, an analysis method and a design method for the TCA are proposed in this paper. Concretely, the analysis and the design method using a numerical method and an analytical method are proposed in this paper. The critical design variables are inspected in detail in this research. The correctness of the proposed methods and the usefulness of the TCA for the high speed switch are verified through an experiment.

Minimization of a Cogging Torque for an Interior Permanent Magnet Synchronous Machine using a Novel Hybrid Optimization Algorithm

Optimization of an electric machine is mainly a nonlinear multi-modal problem. For the optimization of the multi-modal problem, many function calls are required with much consumption of time. To address this problem, this paper proposes a novel hybrid algorithm in which function calls are less than conventional methods. Specifically, the proposed method uses the kriging metamodel and the fill-blank technique to find an approximated solution in a whole problem region. To increase the convergence speed in local peaks, a parallel gradient assisted simplex method is proposed and combined with the kriging meta-model. The correctness and usefulness of the proposed hybrid algorithm is verified through a mathematical test function and applied into the practical optimization as the cogging torque minimization for an interior permanent magnet synchronous machine.

Analysis of a Surface-Mounted Permanent-Magnet Machine with Overhang Structure by Using a Novel Equivalent Magnetic Circuit Model

The rotor overhang is used to enhance the air-gap flux and improve the power density. Due to the asymmetry in the axial direction caused by the overhang, a time consuming 3D analysis is necessary when designing a motor with overhang. To solve this problem, this paper proposes an equivalent magnetic circuit model (EMCM) which takes account overhang effects without a 3D analysis by using effective air-gap length. The analysis time can be reduced significantly via the proposed EMCM. A reduction in the analysis time is essential for a preliminary design of a motor. In order to verify the proposed model, a 3-D finite-element method (FEM) analysis is adopted. 3-D FEM results confirm the validity of the proposed EMCM.

Optimal Design of an Axial Flux Permanent Magnet Synchronous Motor for the Electric Bicycle

Design of an electric machine such as the axial flux permanent magnet synchronous motor (AFPMSM) requires a 3-D finite-element method (FEM) analysis. The AFPMSM with a 3-D FEM model involves too much time and effort to analyze. To deal with this problem, we apply a surrogate assisted multi-objective optimization (SAMOO) algorithm that can realize an accurate and well-distributed Pareto front set with a few number of function calls, and considers various design variables in the motor design process. The superior performance of the SAMOO is verified by comparing it with conventional multi-objective optimization algorithms in a test function. Finally, the optimal design result of the AFPMSM for the electric bicycle is obtained by using the SAMOO algorithm.

A Novel Surrogate-Assisted Multi-Objective Optimization Algorithm for an Electromagnetic Machine Design

To design electric machines, the motor performance, cost, and manufacturing have to be considered. Hence, researchers have called this the multi-objective optimization (MOO) problem in which the goal is to minimize or maximize several objective functions at the same time. In order to solve the MOO problem, various algorithms, such as nondominated sorting genetic algorithm II and multi-objective particle swarm optimization, have been widely used. When these algorithms are applied to the electric machine design, much time consumption is inevitable due to many times of function evaluations using a finite-element method. To solve this problem, a novel surrogate-assisted MOO algorithm is proposed. Its validity is confirmed by comparing the optimization results of test functions with conventional optimization methods. To verify the feasibility of its application to a practical electric machine, an interior permanent magnet synchronous motor is designed.