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The industrial development and the increase in the use of fossil fuels have been accelerating global warming and climate change, thereby causing more frequent and intense natural disasters than ever before. Since electrical facilities are generally installed outdoors, they are greatly affected by natural disasters, thus accidents related to electrical equipment has been on the rise. In this paper, we present the risk rating associated with climate change by analyzing the statistics of electrical fires, electric shock accidents and electrical equipment accidents caused by domestic climate change. Further, we present a risk rating analysis model for electrical fires on a monthly basis through the data analysis of electrical hazards associated with various regional (metropolitan city) climatic conditions (temperature, humidity), and analyze the accident risk rating for natural disasters related to low and high voltage equipment. Through this risk analysis model for each region and type of equipment, we presented a basic prediction model for electrical hazards. Therefore, it is possible to provide electrical safety services in the future by displaying a risk prediction map of electrical hazards for each region and type of electrical equipment through web sites or smart phone apps using the presented analysis data. Further, efforts should be made to increase the robustness or reliability of electrical equipment in order to prevent electrical accidents caused by natural disasters due to climate change in advance.

– This paper describes the accurate inductance measurement of a switched reluctance motor (SRM). Conventionally, the inductance of the SRM is measured using the equivalent circuit of a stator phase or time constant of exponential current transient. This paper presents an effective method to measure the SRM inductance accurately and rapidly using automated voltage integration. The proposed method is validated experimentally by comparison with the existing equivalent circuit method (ECM) and the FEA(finite element analysis) simulation. Key Words : Inductance measurement, Switched reluctance motor, Voltage integration method †Corresponding Author : Dept. of Electrical Engineering Wonkwang University, KoreaE-mail : jaehkim@wku.ac.kr* Dept. of Electrical Engineering, Wonkwang University, Korea Received : March 2, 2015; Accepted : July 27, 2015 1. 서 론 SRM은 가격이 저렴하고 고신뢰성, 고내구성, 단순한 구조 등의 장점과 함께과 직류직권전동기와 유사한 속도-토크 특성을 가지고 있어 산업기기, 항공기, 선반 뿐만 아니라 자동차 전동부품 등의 다양한 분야에 점차 적용이 확대되고 있다[1]. 단점인 고유의 토크 리플과 소음은 지속적인 연구개발을 통하여 개선되고 있으며, 릴럭턴스 토크를 극대화하기 위해 회전자와 고정자 모두 돌극형의 구조를 가지며 권선은 고정자에만 집중권으로 감겨 있어 전자계 구조상 여자 전원이 각 상 권선에 독립적이고 순차적으로 인가되어 구동 되므로 낮은 스위칭 주파수로 운전이 가능하여 고속운전이 가능한 장점이 있는 반면 회전자 위치에 따른 적절한 스위칭 동작을 위해서는 회전자 위치각에 대한 정보를 검출하기 위한 위치 검출 장치가 필수적이라는 취약점을 가지고 있다[2]. 이러한 SRM의 최적제어를 위해서는 필수적으로 정확한 인덕턴스의 값을 측정하는 것이 중요하다. SRM의 인덕턴스는 회전자의 위치와 여자 전류의 함수로써 드라이브의 성능을 결정하는 중요한 파라미터이다[3]. 기존의 인덕턴스 측정방법에는 등가회로를 이용하여 측정하는 방법, 시정수를 이용하여 측정하는 방법, 쇄교자속을 직접 측정하는 방법[4], 전류를 쵸핑하여 측정하는 방법[5], AC중첩방법(AC Superposition)[6] 등이 있다. 등가회로 방법은 정밀한 AC 전압공급기가 필요하며 SRM 고주파 스위칭에 대한 주파수 응답 특성을 제대로 반영하지 못하는 단점이 있으며 시정수 방법은 적절한 시정수 조절을 위해 외부 저항이 필요하다. 쇄교자속을 직접 측정하는 방법은 자기 센서를 이용하여 모터가 조립될 때 모터의 내부에 설치해야하는 불편과 높은 비용으로 인한 단점이 있고 전류를 쵸핑하여 측정하는 방법은 쵸핑구간에서의 제한된 스위칭 주파수와 일정하지 않은 증가시간과 감소 시간에서의 계산으로 인한 오차가 발생한다. AC중첩방법(ACS)은 DC전류에 작은 진폭의 AC 전류를 중첩시킨후 AC 전류는 고정밀 전류계로 AC 전압은 멀티미터로 측정되는 값을 계산하여 인덕턴스를 얻는다. 본 논문에서는 등가회로를 이용한 측정법(ECM : Equivalent Circuit Method)과 본 논문에서 제시할 전압적분법(VIM : Voltage Integration Method)을 비교 분석하였다.

This paper presents a comparative study of torque analysis for synchronous permanent magnet couplings (SPMCs) with parallel- and Halbach-magnetized magnets, using analytical field calculations. On the basis of the magnetic vector potential, we derived analytical solutions for the magnetic field produced by the interaction between the inner and outer PMs for the parallel- and Halbach-magnetized cases. Then, we calculated the magnetic torque using the derived solutions and Maxwell stress tensor. Our analytical results are verified using both 2-D and 3-D finite element analysis and experimental results. We found that SPMC with Halbach-magnetized magnets exhibit dominant pull-out torque than SPMC with parallel magnetized magnets.

This paper discusses the development of a 3.5 kW switched reluctance motor (SRM)-based electric air-conditioning (AC) compressor, focusing primarily on the design aspects of the SRM and the integrated controller. In addition to the increased price of rare-earth magnets, SRM’s operation capability at high speed and high temperature makes the SRM a viable alternative to the permanent magnet motor for electrically driven automotive air conditioning compressors. A compact and energy efficient scroll compressor is designed and constructed. Two feasible SRM topologies are considered, in terms of efficiency, torque ripple, and acoustic noise. Compact drive electronics are designed and employed to drive the SRM-based compressor. The static and dynamic performance is validated by simulation and experiment.

Position estimation that uses only active phase voltage and current is presented, to perform high accuracy position sensorless control of a SRM drive. By extracting the amplitude of the first switching harmonic terms of phase voltage and current for a PWM period through Fast Fourier Transform (FFT), the flux-linkage and position are estimated without external hardware circuitry, such as a modulator and demodulator, which result in increased cost, as well as large position estimation error, produced when the motional back EMF is ignored near zero speed. A two-phase SRM drive system, consisting of an asymmetrical converter and a conventional closed-loop PI current controller, is utilized to validate the performance of the proposed position estimation scheme in comprehensive operating conditions. It is shown that the estimated values very closely track the actual values, in dynamic simulations and experiments.

This paper presents the design of a switched reluctance motor (SRM) for electric air conditioning compressors which are applied to hybrid electric vehicles (EVs). The motor for driving air conditioning compressor which is recently used on EV(electric vehicle) / HEV (hybrid electric vehicle) is PMSM(permanent magnet synchronous motor) or BLDCM(brushless DC motor). However disadvantage of motors that uses permanent magnets are vulnerable to high temperatures because of the demagnetization by the high temperature and the permanent magnet is expensive because of the high price of rare earth materials from China"s monopoly. Therefore, in the automotive insustry is interested in the non-rare-earth motors. SRM has many advantages. it"s resistant to high temperatures, price is cheaper, because there are no permanent magnets and winding in the rotor. Also it"s high relability and efficiency, suitable for high-speed operation because of structure is simple. In this paper, the SRM, non-rare-earth motor, are designed, analyzed and experimented drive to replace an existing electric compressor drive motor.

Elimination of rotor position sensors mechanically coupled with the rotor shaft is attractive to variable speed drives primarily due to increased system reliability and cost reduction. In this regard, search for a simple and robust position sensorless control has been intensified in past few years specifically for low-cost, high-volume applications such as home appliances. This paper describes a new parameter insensitive position sensorless control for switched reluctance motor (SRM) drives satisfying such a need in this market segment. Two consecutive switch-on times of the controllable switch in hysteresis current control are compared to estimate the rotor position and speed. The proposed sensorless control algorithm is very simple to implement since it does not depend on extensive computation or any additional hardware. In addition, the proposed method is robust in that its dynamic performance is least affected by system parameter variations. The proposed approach is demonstrated on a single-controllable-switch-converterdriven SRM with two-phases that lends itself to a system with low cost and compact packaging which comes close to the intended applications. Analysis and simulation results followed by experimental verification are presented to demonstrate the feasibility of the proposed sensorless control method.

A new low-cost, brushless variable-speed drive requiring only a single controllable switch is presented. The proposed converter (referred to as new single-switch converter) overcomes the drawback of the original single-switch-based four-quadrant motor drive in terms of recovery energy circulation. The drive system is realized using an asymmetric two-phase switched reluctance motor (SRM), the proposed converter, and DSP controller. The new drive system retains the unique features of self-starting for all rotor position and four quadrant operation of the original single-switch-based SRM drive system. This paper presents operation principle, modeling, simulation, and design considerations of the converter in conjunction with the motor. Simulation results are based on a nonlinear model of the motor drive system. A prototype drive has been built and tested to verify its practical viability. The experimental results correlate well with the simulation, and demonstrate a performance comparable to conventional asymmetric bridge converter-based drive with two switches per phase. The market relevance of this new drive system is primarily due to its lowest cost structure, packaging compactness, self-starting feature, variable-speed operation and four-quadrant capability. Because of these features, the new drive system offers a viable alternative to conventional fixed-speed brush-commutator motors and variable-speed permanent magnet brushless dc motor drives in many high volume applications in the low-cost, energy efficient, high-volume categories such as fans, blowers, hand tools, and small appliances.

This paper describes a new position sensorless control for the switched reluctance motor (SRM) by monitoring the rate of change of current with respect to the inductance variation. Two consecutive switch-on times in hysteresis current control are compared to calculate the rate of change of current and hence to estimate the rotor position and speed. The proposed sensorless control algorithm is simple to implement as it does not depend on extensive computation or additional hardware. Simulation and experimental results are presented to demonstrate the feasibility of the proposed sensorless control method.

This paper discusses comparison between a CSRM(conventional SRM) and a TSRM(toroidal SRM). Unlike the CSRM, the TSRM has its windings mounted around the stator york instead of the stator pole. Therefore, the TSRM has many different properties in terms of the structure as well as the waveform of phase currents, phase voltages, back-EMF, flux linkages, etc. This paper presents the theoretical comparison between the TSRM and the CSRM followed by simulation results.

This paper presents a low-cost energy-efficient variable-speed drive for high-volume applications, such as home appliances, fans, and hand tools. A new low-cost power converter is proposed, and the drive system is realized using a two-phase switched reluctance motor and the proposed converter. The motor is capable of self-starting at any rotor position and four-quadrant operation. The converter is unique in that it has two capacitors for the energization of each phase and uses the main phase winding as energy storage for the secondary capacitor C2. The converter employs a single-switch-per-phase configuration, hence requiring only two controllable switching devices in total. The converter is inherently suited for two-phase motors having asymmetric stator phases to realize self-starting and speed reversal. Simple starting and C2 voltage control schemes are presented. This paper describes the analysis, modeling, control algorithm, and design considerations for a prototype drive system. Experimental verification and correlation with simulation results are presented. The proposed drive system offers a low-cost brushless variable-speed drive that is a potential alternative for conventional brush-commutator motors in high-volume applications.

Low-cost switched-reluctance-motor (SRM) drive systems are actively sought for high-efficiency home appliances and power tools. Minimizing the number of switching devices has been in power converters that is the main method to reduce drive costs. Single-switch-per-phase converters have been cost effective due to the compactness of the converter package resulting in a possible reduction in their cost. However, some of the single-switch-per-phase converters have the drawbacks that include higher losses and low-system efficiency. In order to overcome these shortcomings, the choice narrows down to the split ac converter through the quantitative analysis in terms of device ratings, cost, switching losses, conduction losses, and converter efficiency. Simulations to verify the characteristics of the converter circuit and control feasibility are presented. The motor drive is realized with a novel two-phase flux-reversal-free-stator SRM and a split ac converter. The efficiency with various loads is numerically estimated and experimentally compared from the viewpoint of subsystem and system in details. The acoustic noise with no load and full load is also compared. The focus of this paper is to compare the considered split ac converter to the asymmetric converter through experiments and demonstrate that the split ac converter is the most advantageous with respect to cost, efficiency, and acoustic noise

A recent increase in the number of diverse leisure activities and family outdoor activities has increased the need for the automobile-embedded vacuum cleaner. To date, this technology has not been applied in Korea and development efforts are not underway. Many of the existing portable cleaners connecting to the lighter jack of the vehicle use a direct current motor (DC motor). However, they do not have sufficient suction power to satisfy consumers; moreover, they have low durability and efficiency. In this paper, we therefore propose a technology for increasing the efficiency of the low-voltage automobile vacuum cleaner by replacing the existing DC motor with a switched reluctance motor (SRM), which has superior durability and efficiency.

This paper discusses development of a 3.5kW switched reluctance motor (SRM)-based electric compressor, focusing primarily on the design aspects of the SRM and the integrated controller. SRM's operation capability at high speed and high temperature in addition to increased price of rare earth magnets makes the SRM a viable alternative to the permanent magnet motor for electrically driven automotive air conditioning compressors. A compact and energy efficient scroll compressor is designed and constructed. Two feasible SRM topologies are considered in terms of efficiency, torque ripple, and acoustic noises. Compact drive electronics are designed and employed to drive the SRM-based compressor. Static and dynamic performance is validated by simulation and experiment.

Elimination of rotor position sensors mechanically coupled with the rotor shaft is attractive to variable speed drives primarily due to increased system reliability and cost reduction. In this regard, search for a simple and robust position sensorless control has been intensified in past few years specifically for low-cost, high-volume applications such as home appliances. This paper describes a new parameter insensitive position sensorless control for switched reluctance motor (SRM) drives satisfying such a need in this market segment. Two consecutive switch-on times of the controllable switch in hysteresis current control are compared to estimate the rotor position and speed. The proposed sensorless control algorithm is very simple to implement since it does not depend on extensive computation or any additional hardware. In addition, the proposed method is robust in that its dynamic performance is least affected by system parameter variations. The proposed approach is demonstrated on a single-controllable-switch-converter-driven SRM with two-phases that lends itself to a system with low cost and compact packaging which comes close to the intended applications. Analysis and simulation results followed by experimental verification are presented to demonstrate the feasibility of the proposed sensorless control method.

A new low-cost, brushless variable-speed drive requiring only a single controllable switch is presented. The proposed converter (referred to as new single-switch converter) overcomes the drawback of the original single-switch-based four-quadrant motor drive [8] in terms of recovery energy circulation. The drive system is realized using an asymmetric two-phase switched reluctance motor (SRM) and the proposed converter. The new drive system retains the unique features of self-starting for all rotor position and four quadrant operation of the original single-switch-based switched reluctance motor drive system. The paper presents operation principle, modeling, simulation, and design considerations of the converter in conjunction with the motor. Simulation results are based on a nonlinear model of the motor drive system. A prototype drive has been built and tested to verify its practical viability. The experimental results correlate well with the simulation, and demonstrate a performance comparable to conventional asymmetric bridge converter based drive with two switches per phase. The market relevance of this new drive system is primarily due to its lowest cost structure, packaging compactness, self-starting feature, variable-speed operation and four-quadrant capability. Because of these features, the new drive system offers a viable alternative for conventional fixed speed brush-commutator motors and variable-speed permanent magnet brushless dc motor drives in many high volume applications in the low-cost, energy efficient, high-volume categories such as fans, blowers, hand tools and home appliances.

Low cost brushless motor drive systems are actively sought for high efficiency home appliances and power tools. Minimizing the number of switching devices has been in power converters is the main method to reduce drive costs. Single-switch-per-phase converters have been cost-effective due to compactness of the converter package resulting in a possible reduction in their cost. However, some of single-switch-per-phase converters have the drawbacks that include higher losses and low system efficiency. In order to overcome these shortcomings, the choice narrows down to the split AC converter through the quantitative analysis in terms of device ratings, cost, switching losses, conduction losses, and converter efficiency. Simulations to verify the characteristics of the converter circuit and control feasibility are presented. The motor drive is realized with a novel two-phase flux-reversal-free-stator switched reluctance motor and a split AC converter. The efficiency with various loads is numerically estimated and experimentally compared in this paper. The acoustic noise with no load and full load is also compared. The focus of this paper is to compare the considered split AC converter to the asymmetric converter through experiments and demonstrate that the split AC converter is the most advantageous with respect to cost, efficiency, and acoustic noise.