Han-Kyeol Yeo

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.

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.

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.

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.

Coupled electromagnetic-thermal analysis of a surface-mounted permanent-magnet motor with overhang structure

Overhang effects should be taken into account to predict performances and temperature distributions of a motor with an overhang structure. This paper investigates the electromagnetic and thermal characteristics of a surfaced-mounted permanent-magnet (SPM) motor with overhang. Moreover, the lumped-parameter thermal model (LPTM) considering overhang effects is proposed. Through the proposed LPTM, the computational time for thermal analysis is reduced considerably in comparison with computational fluid dynamics, and the temperature distributions of the motor are precisely predicted. The results calculated in coupled electromagnetic-thermal analysis are verified experimentally with a 100 W, 20-pole/24-slot SPM motor with overhang.

Cogging torque optimization of in-wheel type motor based on gradient assisted simplex method

Cogging torque reduction of in-wheel type motor is a significant consideration during the machine design. For analysis of in-wheel axial flux machines, 3D FEA is needed. In this manner, despite of good performance of simplex method, a new method which has higher performance is needed. In this paper, gradient assisted simplex method for cogging torque optimization of AFPM for in-wheel motor is proposed. The proposed method reduces the computational cost of the optimization process by adopting the gradient concept.

Electromagnetic and Thermal Analysis of a Surface-Mounted Permanent-Magnet Motor with Overhang Structure

Recently, overhang structures are increasingly used for various applications requiring high torque and power densities in a limited space such as traction motors of electric vehicles and servo motors of robot arms. In the design stage, overhang effects should be taken into account to predict the performances and the temperature rise of a motor with overhang. However, little research has been conducted on the thermal characteristics and analysis methods for a surface-mounted permanent-magnet (SPM) motor with overhang. To address this problem, the electromagnetic and thermal characteristics of the SPM motors with and without overhang are invested in this paper. Specifically, 3-D finite-element method is used in electromagnetic analysis to accurately calculate electromagnetic losses which are heat sources in thermal analysis. Moreover, the lumped-parameter thermal network (LPTN) which can consider overhang effects rapidly and precisely is proposed as an analytical method. Through the proposed LPTN, the computation time for thermal analysis is reduced considerably in comparison with a computational fluid dynamics method, and the temperature rise of the motors are precisely predicted. The results calculated in electromagnetic and thermal analysis are verified experimentally with 0.3 Nm, 20-pole/24-slot SPM motors adopting natural cooling.

Field reconstruction method in axial flux permanent magnet motor with overhang structure

In this paper, the overhang structure which has been used in the radial flux permanent magnet motor was applied to the axial flux permanent magnet (AFPM) motor. We used a field reconstruction method (FRM) to quickly and precisely analyze the overhang effect from overhang structure. The FRM uses the air-gap field generated by a single slot per phase of the stator and by the permanent magnet (PM) on the rotor. In the AFPM motor with overhang structure, because stator and rotor have different length along radial direction, this paper defined new air-gap in the FRM. To validate this work, a 20-pole/30-slot AFPM motor is designed for a 5kW in-wheel motor and the results of FRM and 3-D FEM are compared with experimental data.

A new robust surrogate-assisted multi-objective optimization algorithm for an IPMSM design

For a multi-objective optimization problem applied to the electric machine design, a new robust surrogate-assisted algorithm is proposed in this research. The proposed algorithm can find a robust and well-distributed Pareto front set rapidly and precisely for robust nondominated solutions by using a kriging surrogate model and an uncertainty consideration with worst case scenario. The outstanding performances of the proposed algorithm are verified by a test function. Furthermore, through the application of the optimal design process of the interior permanent magnet synchronous motor, the feasibility of this algorithm is verified.