• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.224-226
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• 1995

This paper presents an algorithm that the gain of the slip calculator is correctly adjusted for the variation of the rotor resistance. In the indirect field oriented controller, if the gain (rotor resistance) of the slip calculator is set the incorrect value, the torque and the flux are not properly controlled. Using of the two torque angles (i.e. stationary torque angle and rotating torque angle), we estimate the rotor resistance, and then adjust the gain of the slip calculator for the variation of the rotor resistance. It has been realized to confirm the validity of the proposed algorithm by the simulation results.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.288-295
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• 1999

This paper presents an application of vector control strategy for 1.2MVA IGBT traction drive for electric railway vehicle. The vector control requires the control of the phase and amplitude of output voltage vector[5]. But in case of traction system far railway vehicle, the one-pulse mode is used in order to utilize the link voltage fully[8]. So it is impossible to control the flux axis current and the torque axis current instantaneously and independently. So this paper proposes the vector control strategy with slip-frequency control at one-pulse mode. And precise switching technique between the two different control structures has been proposed. And the strategy was verified by experimental result with 1.2MVA IGBT inverter with four 210㎾ induction motors.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.189-190
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• 2018

본 논문에서는 유도전동기의 토크 리플 및 스위칭 손실 저감을 위해 전압변조기법인 공간벡터변조(Space Vector Pulse Width Modulation, SVPWM) 기법과 불연속전압변조(Discontinuous Pulse Width Modulation, DPWM) 기법을 혼합하여 사용하는 새로운 변조기법을 제안한다. 제안하는 방식은 지령전압이 최대인 부근에서 SVPWM 기법을 사용하며, 나머지 구간에서는 DPWM 기법을 적용한다. 전 구간 단일기법을 적용할 때와 비교하여 제안하는 방식은 토크 리플 및 스위칭 손실을 효율적으로 저감시킬 수 있으며 시뮬레이션을 통해 타당성을 검증한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.18-25
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• 2022

The cold staring issue of permanent magnet synchronous motors (PMSM) is a chronic problem in the field of PMSM sensorless drives. A traditional starting method, called the I-F method, is widely adopted because of its simple structure. However, when using this method, the pre-defined magnitude and frequency of the starting current should be changed according to the condition of the load and machine inertia. In this paper, a smart and simple algorithm for the cold starting of PMSM is proposed. In the proposed method, an integrated control angle from the estimated electrical rotor speed is used for vector control such as the indirect vector control of the induction machine. Thus, very stable cold starting is performed regardless of the machine load condition or inertia changing.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.33-36
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• 2009

A 1 MW class HTS (High-Temperature Superconducting) synchronous motor has been developed. This motor is aimed to be utilized for industrial application such as large motors operating in large plants. The HTS field coil of the developed motor is cooled by way of neon thermo siphonmechanism and the stator (armature) coil is cooled by water through hollow copper conductor. This paper also describes evaluation of some electrical parameters from performance test results of our motor, which was conducted at steady state in generator mode and motor mode. Open and short circuit tests were conducted in generator mode while a 1.1 MW rated induction machine was rotating the HTS machine. Electrical parameters such as mutual inductance and synchronous inductance are deduced from these tests. Load test was done upto rating torque during motor mode and efficiency was measured at each load torque.

• Journal of the Korea Society of Computer and Information
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• v.16 no.12
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• pp.187-196
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• 2011

Induction motors play a vital role in aeronautical and automotive industries so that many researchers have studied on developing a fault detection and classification system of an induction motor to minimize economical damage caused by its fault. With this reason, this paper extracts robust feature vectors from the normal/abnormal vibration signals of the induction motor in noise circumstance: partial autocorrelation (PARCOR) coefficient, log spectrum powers (LSP), cepstrum coefficients mean (CCM), and mel-frequency cepstrum coefficient (MFCC). Then, we classified different types of faults of the induction motor by using the extracted feature vectors as inputs of a neural network. To find optimal feature vectors, this paper evaluated classification performance with 2 to 20 different feature vectors. Experimental results showed that five to six features were good enough to give almost 100% classification accuracy except features by CCM. Furthermore, we considered that vibration signals could include noise components caused by surroundings. Thus, we added white Gaussian noise to original vibration signals, and then evaluated classification performance. The evaluation results yielded that LSP was the most robust in noise circumstance, then PARCOR and MFCC followed by LSP, respectively.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.588-594
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• 2017

Permanent magnet assisted synchronous reluctance motors (PMa-SynRM) show higher efficiency and power density compared to conventional induction motors for high speed railroad traction systems. Furthermore, 5-phase PMa-SynRMs have lower torque ripple and higher power density than 3-phase systems. Therefore, the 5-phase PMa-SynRM is suitable for high-speed railway traction systems. In this study, 3kw 3-phase and 5-phase PMa-SynRM models were optimized using lumped parameter model and genetic algorithm, and their characteristics were compared. The optimized models are fine-tuned using finite element analysis. The final models of the 3-phase and 5-phase PMa-SynRMs are fabricated and tested to verify the analysis results.

• Journal of the Korea Society of Computer and Information
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• v.18 no.7
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• pp.23-35
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• 2013

This paper proposes an effective technique that is used to automatically extract feature vectors from vibration signals for fault classification systems. Conventional mel-frequency cepstral coefficients (MFCCs) are sensitive to noise of vibration signals, degrading classification accuracy. To solve this problem, this paper proposes spectral envelope cepstral coefficients (SECC) analysis, where a 4-step filter bank based on spectral envelopes of vibration signals is used: (1) a linear predictive coding (LPC) algorithm is used to specify spectral envelopes of all faulty vibration signals, (2) all envelopes are averaged to get general spectral shape, (3) a gradient descent method is used to find extremes of the average envelope and its frequencies, (4) a non-overlapped filter is used to have centers calculated from distances between valley frequencies of the envelope. This 4-step filter bank is then used in cepstral coefficients computation to extract feature vectors. Finally, a multi-layer support vector machine (MLSVM) with various sigma values uses these special parameters to identify faulty types of induction motors. Experimental results indicate that the proposed extraction method outperforms other feature extraction algorithms, yielding more than about 99.65% of classification accuracy.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.1123-1133
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• 2012

This study configuration Vector Control System which is stable and has outstanding Dynamic Characteristics in Very Low Speed Region and Low Speed Region, and proposes Instantaneous Speed Observer and Very Low Speed Control method and vector control system of the speed estimation a using Reduced-Dimensional State Observer. The Observer proposed in this system, by appling Reduced-Dimensional State Observer to Load-Torque estimation and using for speed estimation, implements system composition simply and is capable of accurate Instantaneous Speed estimation in Very Low Speed Region. Also, this study reduces influence by System Noise and suggests an induction motor speed control system which is effective in Load Disturbance, modeling error, estimation noise and so on without changing pole of an Observer.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.57-65
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• 2001

The speed control without a speed sensor is expected strongly to progress reliability, simplicity and cost performance of Induction Motor(I.M) systems. Also, it contributes to expansion of I.M systems into various industrial application fields. This paper investigates a novel speed sensorless control method of I.M considering the secondary resistance identification based on the transientless torque control technique. Especially, this paper aimed at the identification of the secondary resistance simultaneously with speed estimation superposing of sinusoidal flux wave to a constant flux value. Furthermore, the secondary flux with some frequency is controlled independently on torque control. The proposed speed estimation method is derived from a motor circuit equation theoretically and also it can be conducted easily by detecting primary motor currents and primary voltage commands at every sampling time. Some numerical simulations with the assumption of using a pulse width modulation(PWM) voltage source inverter are performed to verify the proposed method.