• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.165-170
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• 2013

This paper presents the iron loss prediction of rotating electric machines taking account of the vector hysteretic properties of electrical steel sheet. The E&S vector hysteresis model is adopted to describe the vector hysteretic properties of a non-oriented electrical steel sheet, and incorporated into finite element analysis (FEA) for magnetic field analysis and iron loss prediction. A permanent magnet synchronous generator is taken as a numerical model, and the analyzed magnetic field distribution and predicted iron loss by using the proposed method is compared with those from a conventional method which employs an empirical iron loss formula with FEA based on a non-linear B-H curve. Through the comparison the effectiveness of the presented method for the iron loss prediction of the rotating machine is verified.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.123-130
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• 2009

The partial discharge (PD) measurement is a very effective method to assess the winding insulation condition of high-voltage machines, since most of the insulation failure processes are directly or indirectly caused by PD. On-line PD measurements, which can detect insulation defects of winding in the early stages on rotating machines in operation, have been accepted as the most important technique. The epoxy mica capacitive coupler is currently and extensively used for on-line detection of PD pulses of high-voltage rotating machines. To evaluate the feasibility of developing a capacitive coupler that is easier to manufacture at a lower cost compared to epoxy mica couplers, a 100pF capacitive coupler made of ceramic material is designed, fabricated and tested for on-line PD measurements of 23 kV electrical machines. A series of electrical tests and accelerated aging tests are performed on the ceramic coupler to evaluate the performance requirements, long-term reliability and thermal stability for in field application. The test results show that the newly developed ceramic coupler provides equal and improved performance at a lower cost compared to epoxy mica couplers, and estimated voltage life is anticipated to surpass 100 years.

• International Journal of Automotive Technology
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• v.4 no.2
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• pp.87-94
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• 2003

Recent advancements of permanent magnet (PM) materials and solid-state devices have contributed to a substantial performance improvement of permanent magnet machines. Owing to the rare-earth PMs, these motors have higher efficiency, power factor, output power per mass and volume, and better dynamic performance than induction motors without sacrificing reliability. Not surprisingly, they are continuously receiving serious considerations for a variety of automotive and propulsion applications. An electric vehicle (EV) requires a high-effficient propulsion system having a wide operating range and a capability of generating a high peak torque for short durations. The improvement of torque-speed performance for these systems is consequently very important, and researches in various aspects are therefore being actively pursued. A great emphasis has been placed on the efficiency and optimal utilization of PM machines. This requires attention to many aspects related to the machine design and overall performance. In this respect, the prediction of iron losses is particularly indispensable and challenging, especially for drives with a deep field-weakening range. The objective of this paper is to present iron loss estimations of a PM motor over a wide speed range. As aforementioned, in EV applications core losses can be significant during high-speed operation and it is imperative to evaluate these losses accurately and take them into consideration during the motor design stage. In this investigation, the losses are predicted by using an analytical model and a 2D time-stepped finite element method (FEM). The results from different analytical approaches are compared with the FEM computations. The validity of each model is then evaluated by these comparisons.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.21-26
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• 2017

According to the data of Korea Occupational Safety and Health Agency, electric shock accidents during recent 11 years exceeded more than 60% in architecture/other and construction work, the countermeasures for safety are required in the harsh environment of a construction site where moving electric machines and equipments are widely used. The establishment of countermeasure for insulation degradation and defect is required, in consideration of increasing trend for accidents caused by defective insulation among low voltage electrical installation each year. The aim of this study is to propose the policy about portable electrical tool standards and/or worker's safety standards for preventing electric shock accidents on safety workings, and is to develop the technology and the safety device to prevent electric shock for accident prevention reduction through experiments. It obtained the followings through this study; statistical data analysis of late about 10 years of electric shock-related industrial accidents analysis and portable electric tools; safety device development of 'device for testing continuous grounding and power shut-down' to prevent electric shock from portable electric tools. Furthermore, developed results and proposal in this study will help to prevent the electric shock accidents from portable electric tools and will be expected the utilization of policy formulation, educational data and field supplement of the safety device, and etc.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.55-58
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• 1995

An optimum design method of electric machines using neural network is presented. In this method, two multi - layer perceptrons of analysis and design neural network are used in optimizing process. A preliminary model of linear induction motor for subway is designed by the electric and magnetic loading distribution method and then optimized by presented method.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.343-345
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• 1996

In the case of synchronous machines, certain power system disturbances cause current to assume negative values when no static converter is present. But the converter prevents negative current from flowing, so that overvoltages occur. The overvoltages can be effectively limited as crowbar circuit using GTO. The crowbar circuit with current limiting resistor absorbs energy when overvoltage comes from power system repeatedly. The newly proposed circuit is verified through simulation and experiment

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1096-1106
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• 2013

This paper presents the control of a Permanent Magnet Electric Variable Transmission (PM-EVT) for Hybrid Electric Vehicles (HEVs). Consisting of two electric machines, the EVT realizes the power split function in an electromagnetic way rather than in a mechanical way. A specific PM-EVT has been designed for Toyota Prius II. The control scheme of the entire vehicle is deduced using the Energetic Macroscopic Representation methodology. The energy management strategy yields local control references. A specific attention is paid for the field weakening for wide speed range. Simulation results are provided to illustrate the EVT modeling and control.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.282-287
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• 2013

The concentrated winding configurations offer significant advantage for reducing end windings. These machines are generally used in low speed high torque application due to relatively low copper loss. However, numbers of fractional slot construction make the designer hard to properly choose pole and slot numbers for the certain application. This paper provides the general information of possible fractional slot concentrated double layer winding machine.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.420-423
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• 1995

The electric arc welding machine with high-frequency inverter is studied in this paper which could make more saving in energy than conventional ones with inherent low efficiency. The inverter circuit has been already adopted to special welding machines such as MIG and TIG for improving operating performances so much. But this adoption has not be applied to conventional ac arc welding machine until now. The proposed technology for higher efficiency is to apply the high frequency inverter, together with noise-cut transformer. Overall output characteristics are investigated in aspect of cost and circuit performance. The proposed system is conducted practical experiments using PWM controller.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1244-1255
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• 2015

This paper presents a new multi-machine robust control based on an electric differential system for electric vehicle (EV) applications which is composed of four in-wheel permanent magnet synchronous motors. It is based on a new master-slave direct torque control (DTC) algorithm, which is used for the control of bi-machine traction systems based on a speed model reference adaptive system observer. The use of an electric differential in the design of a new EV constitutes a technological breakthrough. A classical system with a multi-inverter and a multi-machine comprises a three-phase inverter for each machine to be controlled. Another approach consists of only one three-phase inverter for several permanent magnet synchronous machines. The control of multi-machine single-inverter systems is the subject of this study. Several methods have been proposed for the control of multi-machine single-inverter systems. In this study, a new master-slave based DTC strategy is developed to generate an electric differential system. The entire system is simulated by Matlab/Simulink. The simulation results show the effectiveness of the new multi-machine robust control based on an electric differential system for use in EV applications.