Seok-Myeong Jang

Bio: Seok-Myeong Jang is an academic researcher from Chungnam National University. The author has contributed to research in topics: Magnet & Rotor (electric). The author has an hindex of 23, co-authored 160 publications receiving 1774 citations.

Design and Analysis of a High-Speed Brushless DC Motor for Centrifugal Compressor

Abstract: This paper describes the design and analysis of a high-speed and high-power density BLDC motor for a 50-kW, 70 000-rpm class centrifugal compressor. Design criteria and power loss analysis of the high-speed machine structure are described by analytical method, and the results are validated by finite element method. And then, the prototype machine has been fabricated and tested. The experimental results confirmed the validity of the proposed design and analysis scheme of the high-speed BLDC motor

A Design Approach to Reduce Rotor Losses in High-Speed Permanent Magnet Machine for Turbo-Compressor

Abstract: Recently, high-speed centrifugal turbo-compressors have been under intensive research and development. Since, compared to conventional compressors, high-speed centrifugal compressors have numerous qualities such as simple structure, light weight, small size, and high efficiency, etc. In order to maintain the mechanical integrity of a high-speed permanent magnet (PM) machine rotor intended for high-speed operation, the rotor assembly is often retained within a stainless steel or carbon-fiber sleeve. The sleeve is exposed to fields produced by the stator from either the slotting or the mmf harmonics that are not synchronous with the rotor. These non-synchronous fields cause the significant rotor losses. An optimum design of PM machines requires the accurate prediction for these rotor losses. On the basis of analytical field analysis and 2D finite element analysis (FEA), this paper deals with the rotor losses in high-speed PM machine. In particular, the difference of the rotor losses between the Inconel718 and Carbon-Fiber/Epoxy sleeve is quantitatively made clear in this work.

Analytical Torque Calculations and Experimental Testing of Permanent Magnet Axial Eddy Current Brake

Abstract: This paper discusses the braking torque and normal force analysis of axial flux permanent magnet (AFPM)-type eddy current brakes (ECB) on the basis of an analytical field computation using a space harmonic method. On the basis of the magnetic vector potential and a 2D polar coordinate system, permanent magnets considering the eddy current effect are obtained. Additionally, by utilizing the derived analytical field solutions, the braking torque and normal force are predicted. Finite element analysis is employed to confirm the validity of the analysis and compare it with the experimental results obtained from the prototype AFPM-type ECB.

Improved Analytical Model for Electromagnetic Analysis of Axial Flux Machines With Double-Sided Permanent Magnet Rotor and Coreless Stator Windings

Abstract: This paper deals with the experimental verification and electromagnetic analysis of an axial flux machine with a double-sided permanent magnet (PM) rotor and coreless stator windings, based on analytical field computation. Employing a magnetic vector potential and a 2-D analytical model, magnetic fields produced by PMs are obtained. The 3-D problem is solved by introducing a special function for the radial position. Then, the analytical solutions for back emf, electromagnetic torque, and efficiency of the PM-type axial flux machines are derived by using the magnetic field solutions and considering simple equivalent circuits. The analytical results are validated extensively by 3-D FE results. Test results such as back-emf, torque, and efficiency measurements are also presented to show the effectiveness of the analyses.

Vibration Analysis and Measurements Through Prediction of Electromagnetic Vibration Sources of Permanent Magnet Synchronous Motor Based on Analytical Magnetic Field Calculations

Abstract: This study is devoted to the analysis of the vibration characteristics of a permanent magnet synchronous motor (PMSM) through investigation into its electromagnetic vibration sources. For this purposed, we derive analytical solutions for the magnetic fields generated by permanent magnets (PMs) in terms of a magnetic vector potential and a two-dimensional (2-D) polar coordinate system. A 2-D permeance function is also introduced in order to consider slotting effects. The electromagnetic vibration sources such as torque ripple, cogging torque, and radial force density are analyzed using these solutions. The analytical results are validated extensively with finite element (FE) analyses. The fast Fourier transformation (FFT) analysis is employed for investigating the specific harmonic orders of the electromagnetic vibration sources that affect the vibration of the PMSM. Finally, mechanical modal analysis results and test results such as vibration measurements are obtained to confirm the validity of the analysis methods presented in this paper.

High-Speed Electrical Machines: Technologies, Trends, and Developments

Abstract: This paper reviews the current technologies used in high-speed electrical machines through an extensive survey of different topologies developed and built in the industry and academia for several applications. Developments in materials and components, including electrical steels and copper alloys, are discussed, and their impact on the machines' operating physical boundaries is investigated. The main application areas pulling the development of high-speed machines are also reviewed to better understand the typical performance requirements.

A comprehensive review of Flywheel Energy Storage System technology

Abstract: Energy storage systems (ESSs) play a very important role in recent years. Flywheel is one of the oldest storage energy devices and it has several benefits. Flywheel Energy Storage System (FESS) can be applied from very small micro-satellites to huge power networks. A comprehensive review of FESS for hybrid vehicle, railway, wind power system, hybrid power generation system, power network, marine, space and other applications are presented in this paper. There are three main devices in FESS, including machine, bearing, and Power Electronic Interface (PEI). Furthermore, advantages and disadvantages all of them have been presented. In addition a brief review of new and conventional power electronic converters used in FESS, have been discussed. Finally, practical ways to develop this technology in the future are presented.

Electrical Machines for High-Speed Applications: Design Considerations and Tradeoffs

Abstract: The high-speed (HS) electric machines are gaining attention in several different applications, and the development of advanced materials, electronic components, and control algorithms is pushing ahead the technological speed limits. In the electromagnetic sizing of HS machines, the mechanical and thermal involvements are very tight to make it necessary to deal with all the different aspects at the same time. This paper aims to summarize and discuss the electrical and the mechanical aspects involved in the HS machine design, highlighting the main issues and the tradeoffs that the designer has to consider. Furthermore, the correlation between volume reduction and speed increase, based on commercial high-frequency rotor-stator units, is also presented.

Flywheel energy storage systems: Review and simulation for an isolated wind power system

Abstract: In flywheel based energy storage systems (FESSs), a flywheel stores mechanical energy that interchanges in form of electrical energy by means of an electrical machine with a bidirectional power converter. FESSs are suitable whenever numerous charge and discharge cycles (hundred of thousands) are needed with medium to high power (kW to MW) during short-time periods (seconds–minutes). Monitoring of the FESS state of charge is simple and reliable as only the spinning speed is needed. The materials for the flywheel, the type of electrical machine, the type of bearings and the confinement atmosphere which all together determine the FESSs energy efficiency (>85%) are reviewed. Main FESS applications: power quality, traction and aerospace are presented. Additionally in this paper it is presented the simulation of an isolated wind power system (IWPS) consisting of a wind turbine generator (WTG), a consumer load, a synchronous machine (SM) and a FESS. A low-speed iron flywheel driven by an asynchronous machine (ASM) is sized for the presented IWPS. The simulation results with graphs for system frequency, system voltage, active powers of the different elements, and FESS-ASM speed, direct and quadrature currents are presented showing that the FESS effectively smoothes the wind power and consumer load variations.

On the Speed Limits of Permanent-Magnet Machines

Abstract: Permanent-magnet (PM) machines are considered the most suitable machine type for very high speed applications. Still, due to the growing demand for the ever higher rotational speeds, PM machines are approaching their limits. The focus of this paper is the different factors that lie behind the inherent speed limitations of PM machines. The limits-thermal, elastic, and rotor dynamical-are defined, classified, and correlated to basic machine parameters.