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Switched reluctance machine (SRM) has progressed as a suitable contender in the family of electrical machines for its high starting torque and better performance in different operating conditions. The need for accurate modeling of this machine is, therefore, dependent on the accurate determination of losses of which iron loss is exigent. This article aims to determine iron loss from the equivalent circuit parameters of the machine based on the input data tables that are directly obtained from the experiments carried out on an existing four-phase, bifilar wound SRM. The procedure and necessary steps for the loss separation method are well defined and supported by the theoretical and practical results. The experimental determination of the iron losses has been compared with the predicted results under the same operating conditions. [ABSTRACT FROM AUTHOR]

In this article, a new low-cost small-scale three-phase brushless motor topology is proposed. This is a new topology for self-excitation of brushless wound rotor synchronous motor investigated initially for rated speed. For brushless excitation, the stator is designed to contain two windings, namely, three-phase armature winding and exciter winding. The rotor consists of two windings, that is, harmonic winding and field winding, and a diode rectifier. An inverter feeds the three-phase armature winding which is connected in series through an uncontrolled three-phase rectifier to a single exciter winding. When the current is supplied from the inverter, both the armature and exciter windings are energized eventually producing a flux in the air gap. Since the flux produced by the exciter winding is not synchronized with the field winding, it produces a harmonic to be intercepted by the harmonic winding on the rotor. Eventually, the voltage produced in the harmonic winding is used to feed dc current to the field winding for brushless operation. The results obtained by 2-D finite-element analysis (FEA) validate the brushless operation of the motor. The proposed motor is analyzed basically for topology verification with the FEA results. Since the topology can be verified, further effort can be put to investigate such low-cost topologies for brushless wound rotor synchronous motor. It can be an alternative to a costly permanent magnet synchronous motor for specific applications. [ABSTRACT FROM AUTHOR]

This paper reports an energy-efficient permanent magnet (PM) zero-holding-energy magnetic contactor (ZMC) that consumes no energy while maintaining an open or closed state. Conventional solenoid magnetic contactor (MC) technology has several critical drawbacks, including high continuous energy consumption, continuous vibration, and low reliability. The proposed ZMC substantially reduces energy consumption and heat generation, produces no vibration, and provides increased reliability. Traditional MC analysis typically requires computationally expensive finite element analysis (FEA). To reduce the analysis costs, a recently proposed fast and accurate nonlinear transient path energy method (NT-PEM) is utilized to significantly reduce analysis time and costs. Analysis accuracy was verified experimentally using a fabricated ZMC prototype. The economic and environmental benefits of the proposed ZMC confirm its significant potential as an energy-efficient eco-friendly alternative to traditional MC technology. ZMC is particularly promising for vehicular micro-grids due to the prolongation of the lifetime of batteries owing to reduced energy consumption. [ABSTRACT FROM AUTHOR]

Optimization of an electric machine is a nonlinear multi-variable problem. For optimization of the nonlinear multi-variable problem, many function evaluations are required, which in turn requires much time. To address this problem, we propose a novel optimization algorithm of which the convergence speed, accuracy, and reliability are superior compared to those of widely used conventional algorithms. The performance of the proposed algorithm is verified through mathematical test functions and applied to a practical optimization scenario of cogging torque minimization for an interior permanent magnet synchronous machine. [ABSTRACT FROM AUTHOR]

The conventional topology optimization (TO) algorithm for an electric machine has a critical problem as the derivation of the impractical model to manufacture. In the case of a conventional step optimization, such as shape optimization (SO) after TO, the optimized model by TO is seriously distorted. To solve these problems, a hybrid optimization algorithm that conducts SO and TO simultaneously with the pre-processing and the post-processing is proposed in this paper. [ABSTRACT FROM AUTHOR]

When a conventional optimization algorithm is applied to diverse problems, the performance is not guaranteed because the optimization algorithm is tuned properly to a specific problem. To address this problem, a novel strategy-selecting hybrid optimization algorithm (SSHOA) is proposed. The proposed algorithm can autonomously and intelligently establish a strategy, which offers a better fitting algorithm according to a varying problem situation. The efficiency, accuracy, and reliability of the SSHOA are verified via mathematical test functions. To confirm electromagnetic performance capabilities, the proposed algorithm is applied to the optimization of an outer rotor permanent magnet machine. [ABSTRACT FROM AUTHOR]

The characteristics analysis of an electric machine requires the finite-element method. Hence, a large amount of computation occurs in the design process to take into account uncertainties as the manufacturing tolerances. In this paper, an efficient and useful multimodal optimization algorithm using the kriging surrogate model is proposed for the robust optimization of an electric machine. However, the conventional kriging (CK) method has a memory problem in multi-dimensional problem due to the enlarged correlation matrix. Thus, a sub-domain kriging (SDK) strategy and improved Latin hypercube sampling (ILHS) are proposed not only to solve the memory problem of the CK method, but also to increase the convergence speed. In addition, a gradient-free sensitivity index is proposed for robust optimization in order to address the conventional first and second gradient index which causes a numerical error. The outstanding performance of the proposed algorithm is verified by comparing with other optimization methods via several mathematical test functions which includes multi-dimensional problem. Moreover, the proposed algorithm is applied to a cogging torque reduction design case for interior permanent magnet motor. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To optimize an interior permanent magnet synchronous motor (IPMSM) design for a fuel cell electric vehicle, a new surrogate-assisted multi-objective optimization (MOO) algorithm is proposed in this paper. The proposed algorithm is a multi-objective algorithm (MOO) that can account for three kinds of objectives such as the torque amplitude, torque ripple, and magnet usage simultaneously to improve the power transmission and to reduce the noise, vibration, and cost for various design variables. While the conventional MOO algorithms have a series that requires many function evaluations, especially considering many objectives and design variables, the proposed algorithm can create an accurate and well-distributed Pareto front set with few function evaluations. In comparison with the conventional MOO algorithms, the outstanding performance of the proposed algorithm is verified. Finally, the proposed algorithm is applied to an optimal design process of an IPMSM. [ABSTRACT FROM AUTHOR]

This paper presents a design and analysis method for a novel hybrid flux permanent-magnet (PM) machine for a high-power density. By combining radial and axial flux machines with integrated windings, the air-gap flux density is increased, and an overhang structure of the PM and additional magnetic cores are applied to increase the power density. For the analysis and design of the proposed motor, a time-consuming 3-D finite-element analysis (FEA) is required owing to its unique structure. To address this problem, a correct and rapid novel analysis method is proposed using an equivalent 2-D conversion method. The accuracy of the proposed analysis method and the usefulness of the proposed motor are confirmed via the 3-D FEA and experimental results. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

The selection of optimal parameters during the design of an electric motor is a multivariable and multimodal optimization problem that requires a considerable amount of computational calculation time. To solve this type of problem, this paper proposes a novel multimodal optimization algorithm that is assisted by a surrogate model using the newly developed compressed sensing theory. Its effectiveness is confirmed by comparing the optimization results for test functions with the results of conventional optimization methods. These results show that the proposed method has more rapid and accurate convergence characteristics than conventional approaches. To verify the feasibility of its application to electric motors, an in-wheel motor is designed using the proposed algorithm. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

This paper presents a magnetic field analysis of a surface-mounted permanent magnet machine with an overhang structure wherein the rotor axial length exceeds that of the stator. A 2-D analytic method using a lumped magnetic circuit model (LMCM) is proposed for more rapid computation of the overhang effect compared with a conventional 3-D or quasi-3-D finite element analysis (FEA). In the LMCM, the effective overhang length is calculated, and a leakage flux generated in the overhang region is estimated. The accuracy and usefulness of the proposed analytic method is confirmed through the 3-D FEA and the experimental results according to the diverse overhang length, the number of slot/pole, and stator core length. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

Due to the continuous energy consumption in a closing coil for the maintenance of a closed state, the conventional solenoid type MC has serious problems such as inefficient energy consumption, welding in contacts, vibration, and noise. To address these problems, an advanced MC using a permanent magnet, an inter-locking system, and a guiding structure is proposed and named the MCPIG (magnetic contactor using permanent magnet, inter-locking system, and guiding structure) in this paper. Analysis method and design strategy are proposed for the MCPIG in this research. Through examining the experimental data of a prototype, the practicality of the proposed analysis and design method as well as the usefulness of the MCPIG for 220 V 85 AF MC are verified. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

When a motor is running under a load condition, it is difficult to analyze and measure the diverse types of loss occurring in the motor. To address this problem, the analysis and the measurement methods that assess the losses in a motor under a load condition are proposed in this paper. In high power density types of motors, eddy current loss is the major type of loss. A three-dimensional finite element method has been used for the analysis of the eddy current loss, which requires the much time and effort in the design process. To solve this problem, in this study we propose an analytic method that can be used for the analysis of the eddy current loss. The proposed loss analysis and measuring methods for a permanent magnet motor under a load condition are validated using a prototype. [ABSTRACT FROM AUTHOR]

The solenoid magnetic actuator has been widely used as an actuator for MS (magnetic switch). Thus, conventional MSs continuously consume electrical power to maintain a closed state. To address this problem, an innovative structure which uses a permanent magnet to generate holding force in the closed state without electrical power is suggested in this paper. Further, the permanent magnet is dedicated to the opening operation and the closing operation by means of its magnetic force. In other words, an eco-friendly MS is proposed in this research. However, this structure has a critical problem in that, if unexpected external force is applied to the MS when in the open state, the MS returns to the closed state by the force of the permanent magnet and remains in the closed state, causing an unintended operation of the load. To solve this problem, a novel inter-locking mechanism is proposed. Hence, we termed the proposed novel MS the MSPI (magnetic switch using a permanent magnet and an inter-locking system). In addition, analysis and design methods for the MSPI are proposed in this paper. The usefulness of the MSPI and the accuracy of the analysis and design methods are confirmed through an experiment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

The information in the published version of [1] contained incorrect information about the affiliation of the authors. The correct affiliations are listed above. [ABSTRACT FROM AUTHOR]