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Jong-Jae Lee

Bio: Jong-Jae Lee is an academic researcher from Pohang University of Science and Technology. The author has contributed to research in topics: Inductor & Buck–boost converter. The author has an hindex of 5, co-authored 6 publications receiving 838 citations.

Papers
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Journal ArticleDOI
TL;DR: An online induction motor diagnosis system using motor current signature analysis (MCSA) with advanced signal-and-data-processing algorithms is proposed, able to ascertain four kinds of motor faults and diagnose the fault status of an induction motor.
Abstract: In this paper, an online induction motor diagnosis system using motor current signature analysis (MCSA) with advanced signal-and-data-processing algorithms is proposed. MCSA is a method for motor diagnosis with stator-current signals. The proposed system diagnoses induction motors having four types of faults such as breakage of rotor bars and end rings, short-circuit of stator windings, bearing cracks, and air-gap eccentricity. Although MCSA is one of the most powerful online methods for diagnosing motor faults, it has some shortcomings, which degrade performance and accuracy of a motor-diagnosis system. Therefore, advanced signal-and-data-processing algorithms are proposed. They are composed of an optimal-slip-estimation algorithm, a proper-sample-selection algorithm, and a frequency auto search algorithm for achieving MCSA efficiently. The proposed system is able to ascertain four kinds of motor faults and diagnose the fault status of an induction motor. Experimental results obtained on 3.7-kW and 30-kW three-phase squirrel-cage induction motors and voltage-source inverters with a vector-control technique are discussed

539 citations

Journal ArticleDOI
TL;DR: A bridgeless boost rectifiers with low conduction losses and reduced diode reverse-recovery problems is proposed for power-factor correction and the linear peak current mode control is employed for the proposed boost rectifier.
Abstract: A bridgeless boost rectifier with low conduction losses and reduced diode reverse-recovery problems is proposed for power-factor correction. The proposed boost rectifier can reduce the conduction losses and alleviate the diode reverse-recovery problems by using a coupled inductor and two additional diodes. Zero-current turn-off of the output diodes is achieved, and the reverse-recovery currents of the additional diodes are slowed down to reduce the diode reverse-recovery losses. All inductive components are realized on a single magnetic core by utilizing the leakage inductance of the coupled inductor. Furthermore, for the use of this topology in the practical design, the linear peak current mode control is employed for the proposed boost rectifier. A detailed analysis and a control strategy are presented. Experimental results for a 300-W prototype are also discussed to show the performance of the proposed boost rectifier

203 citations

Journal ArticleDOI
09 Oct 2006
TL;DR: In this paper, a continuous-conduction-mode SEPIC converter with low reverse-recovery loss is proposed for power factor correction, which can reduce the reverse- recovery loss of the diodes and improve the power efficiency.
Abstract: A continuous-conduction-mode SEPIC converter with low reverse-recovery loss is proposed for power factor correction. The proposed SEPIC converter can reduce the reverse- recovery loss of the diodes and improve the power efficiency. By utilising a coupled inductor and an additional diode, zero-current turn-off of the output diode is achieved. The reverse-recovery current of the additional diode is reduced by the leakage inductor of the coupled inductor. The proposed SEPIC converter provides high power efficiency and high power factor compared to the conventional PFC circuits employing the SEPIC converter. An operation principle and a detailed analysis of the proposed converter are presented. Experimental results are discussed for a 300 W (330 V/0.9 A) prototype under the universal input voltage (90-265 V). It is shown that the efficiency of the SEPIC converter can be significantly improved.

65 citations

Journal ArticleDOI
TL;DR: A new multiple-coupled inductor (MCI) is proposed for good cross regulation among low output voltages, high power density, and reduced converter volume, and a current doubler rectifier and a self-driven synchronous rectifier are presented to achieve high efficiency.
Abstract: A new multiple-coupled inductor (MCI) is proposed for good cross regulation among low output voltages, high power density, and reduced converter volume. Moreover, a current doubler rectifier and a self-driven synchronous rectifier are presented to achieve high efficiency. The structure of the MCI is composed of four windings on a common core, and has the properties of a current doubler and good cross regulation. A dc-dc half-bridge converter using the proposed MCI is analyzed and designed for 40-W low output voltages (3.3, 4.5 V). This converter is very suitable for high current and low voltage applications. It is shown via experimental results that efficiency of over 90% and cross regulation of about 5% are achieved

55 citations

Journal ArticleDOI
06 Feb 2006
TL;DR: In this article, an asymmetrical PWM half-bridge convertor with independently regulated multiple outputs is proposed, where each output is regulated by its own feedback control circuit and a duty ratio of the primary switch is determined mainly by the input voltage of the convertor.
Abstract: An asymmetrical PWM half-bridge convertor with independently regulated multiple outputs is proposed Each output is regulated by its own feedback control circuit and a duty ratio of the primary switch is determined mainly by the input voltage of the convertor Thus cross regulation between outputs is almost eliminated In addition, the proposed convertor can achieve zero-voltage switching (ZVS) by complementary control The operation of the proposed convertor is analysed and the concepts of the proposed convertor were verified by experimental results obtained from a 24 V/6 A, 12 V/4 A prototype

28 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: This paper investigates diagnostic techniques for electrical machines with special reference to induction machines and to papers published in the last ten years, and research activities are classified into four main topics.
Abstract: This paper investigates diagnostic techniques for electrical machines with special reference to induction machines and to papers published in the last ten years. A comprehensive list of references is reported and examined, and research activities classified into four main topics: 1) electrical faults; 2) mechanical faults; 3) signal processing for analysis and monitoring; and 4) artificial intelligence and decision-making techniques.

1,003 citations

Journal ArticleDOI
TL;DR: In this paper, a systematic review of bridgeless power factor correction (PFC) boost rectifiers, also called dual-boost PFC rectifiers is presented, where loss analysis and experimental efficiency evaluation for both CCM and DCM/CCM boundary operations are provided.
Abstract: In this paper, a systematic review of bridgeless power factor correction (PFC) boost rectifiers, also called dual boost PFC rectifiers, is presented. Performance comparison between the conventional PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier family is performed. Loss analysis and experimental efficiency evaluation for both CCM and DCM/CCM boundary operations are provided.

739 citations

Proceedings ArticleDOI
07 May 2007
TL;DR: In this article, a systematic review of bridgeless PFC boost rectifiers, also called dual boost PFC rectifiers is presented, where design considerations and experimental results in both CCM and DCM/CCM boundary operations are provided.
Abstract: In this paper, a systematic review of bridgeless PFC boost rectifiers, also called dual boost PFC rectifiers, is presented. Performance comparison between the conventional PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier family is performed. Design considerations and experimental results in both CCM and DCM/CCM boundary operations are provided.

588 citations

Journal ArticleDOI
TL;DR: New models for the influence of rolling-element bearing faults on induction motor stator current are described, based on two effects of a bearing fault: the introduction of a particular radial rotor movement and load torque variations caused by the bearing fault.
Abstract: This paper describes a new analytical model for the influence of rolling-element bearing faults on induction motor stator current. Bearing problems are one major cause for drive failures. Their detection is possible by vibration monitoring of characteristic bearing frequencies. As it is possible to detect other machine faults by monitoring the stator current, a great interest exists in applying the same method for bearing fault detection. After a presentation of the existing fault model, a new detailed approach is proposed. It is based on the following two effects of a bearing fault: 1. the introduction of a particular radial rotor movement and 2. load torque variations caused by the bearing fault. The theoretical study results in new expressions for the stator current frequency content. Experimental tests with artificial and realistic bearing damage were conducted by measuring vibration, torque, and stator current. The obtained results by spectral analysis of the measured quantities validate the proposed theoretical approach.

455 citations