• Proceedings of the KIEE Conference
• /
• 1996.11a
• /
• pp.9-11
• /
• 1996

The Switched Reluctance Motor is an electric machine in which torque is produced by the tendency of its movable part to move to a position where the inductance of the excited winding is maximized. The main advantages of this motor lie in the simple robust construction and low manufacturing cost. In this paper, we describe the design features of single-phase switched reluctance motor for low-power variable-speed drives.

• Proceedings of the KIEE Conference
• /
• 1993.07a
• /
• pp.335-337
• /
• 1993

An integral-augmented variable structure system is suggested for the control of an uncertain SISO systems without the reaching phase problems. The integral-augmented sliding surface is defined in order to remove the reaching phase, then it is designed using the optimal technique. The example results show the effectiveness of the algorithm.

• Journal of Biomedical Engineering Research
• /
• v.15 no.2
• /
• pp.143-150
• /
• 1994

Wall shear rate or stress is believed to be a major hemodynamic variable influencing atherosclerosis and artery-graft anastomic intimal hyperplasia. The purpose of this study is to verify the effects of radial wall motion, artery-graft compliance and diameter mismatch, and impedance phase angle on the wall shear rate distribution near an end-to-end artery-graft anastomosis model. The results show that radial wall motion of the elastic artery model lowers the mean wall shear rates under pulsatile flow condition by 15 to 20 % comparing to those under steady flow condition at the same mean flow rate. Impedance phase angle seems to have small effects on the mean and amplitude of the wall shear rate distribution. In order to study the effects of compliance and diameter mismatch on the wall shear rates, two models are studied-Model I has 6% and Model I has 6% and Model II has 11% smaller graft diameter. Divergent geometry caused by diameter mismatch near the distal sites reduces the mean wall shear rates significantly, and this low shear region is believed to be prone to intimal hyperplasia.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.5
• /
• pp.647-657
• /
• 2011

The present paper proposes a sliding mode control with fixed switching frequency for three-phase three-leg voltage source inverter based four-wire shunt active power filter. The aim is to improve phase current waveform, neutral current mitigation, and reactive power compensation in electric power distribution system. The performed sliding mode for active filter current control is formulated using elementary differential geometry. The discrete control vector is deduced from the sliding surface accessibility using the Lyapunov stability. The problem of the switching frequency is addressed by considering hysteresis comparators for the switched signals generation. Through this method, a variable hysteresis band has been established as a function of the sliding mode equivalent control and a predefined switching frequency in order to keep this band constant. The proposed control has been verified with computer simulation which showed satisfactory results.

• Journal of Korean Institute of Industrial Engineers
• /
• v.27 no.2
• /
• pp.169-175
• /
• 2001

Most of studies on automated storage/retrieval (AS/R) system assumed that storage capacity is given, although it is a very important decision variable in the design phase. We propose a simple algorithm to estimate the required storage capacity, i.e., number of aisles and number of openings in vertical and horizontal directions in each aisle, of an AS/R system under stochastic demand, in which storage requests occur endogenously and exogenously while the retrieval requests occur endogenously from the machines. Two design criteria, maximum permissible overflow probability and maximum allowable storage/retrieval (S/R) machine utilization, are used to compute the storage capacity. This model can be effectively used in the design phase of new AS/R systems.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1016-1019
• /
• 1993

A low-pass L-C filter has been adopted for conversion of frequency variable 3 phase PWM waveform to a grid power line and it is used for attenuation of harmonics in the VSI PWM Inverter. A optimum design of the L, C parameters was derived. The result of the study show that the inductor L seems to have a certain air gap for linear I-V characteristics and the resonant frequency of the filter must be set below the 5th harmonics of the grid power line. Further, the voltage drop in L must be within a adequate limit compared to grid power voltage.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1026-1029
• /
• 1993

Inherent speed-torque performance of Switched Reluctance Motor is similar to that of series wound DC motor. Thus, the speed of the motor is extremely regulated according to load torque. For the purpose of controlling the speed and torque of SRM it is necessary to change the applied DC link voltage or the switch-ON and switch-OFF angles which control the phase current of the motor. This paper describes speed-torque characteristics of an integral horse power Switched Reluctance Motor by adjusting the switch-ON and switch-OFF angles. Speed at rated load torque can be regulated by adjusting the switching angles and the control scheme is applied to 2kW, 3 phase, 6/4 SRM.

• Journal of the Korea Society for Simulation
• /
• v.10 no.3
• /
• pp.71-82
• /
• 2001

Considering material handling delay which occurs between storage and processing stations, we propose an algorithm to estimate the required storage capacity, i.e., number of aisles and number of openings in vertical and horizontal directions in each aisle, of an automated storage/retrieval(AS/R) system. Due to the random nature of storage and retrieval requests, proportion of single and dual commands is not known in advance. Two design criteria, maximum permissible overflow probability and maximum allowable storage/retrieval(S/R) machine utilization, are used to compute the storage capacity. Most of studies assume that storage capacity of AS/R systems is given, although it is a very important decision variable in the design phase. Therefore, the proposed model can be effectively used in the design phase of new AS/R systems.

• Communications for Statistical Applications and Methods
• /
• v.26 no.1
• /
• pp.11-25
• /
• 2019

The present paper utilizes auxiliary information to neutralize the effect of non-response for estimating the population mean. Improved ratio type estimators for population mean have been proposed and their properties are studied. These estimators are suggested for both single phase sampling and two phase sampling in presence of non-response. Empirical studies are conducted to validate the theoretical results and demonstrate the performance of the proposed estimators. The proposed estimators are shown to perform better than those used by Cochran (Sampling Techniques (3rd ed), John Wiley & Sons, 1977), Khare and Srivastava (In Proceedings-National Academy Science, India, Section A, 65, 195-203, 1995), Rao (Randomization Approach in Incomplete Data in Sample Surveys, Academic Press, 1983; Survey Methodology 12, 217-230, 1986), and Singh and Kumar (Australian & New Zealand Journal of Statistics, 50, 395-408, 2008; Statistical Papers, 51, 559-582, 2010) under the derived optimality condition. Suitable recommendations are put forward for survey practitioners.

• Journal of Power Electronics
• /
• v.19 no.3
• /
• pp.714-726
• /
• 2019

This paper proposes a hybrid-boost Modular Multilevel Converter (MMC) for the Medium-Voltage (MV) Variable Speed Drives (VSDs) employed in subsea applications, such as oil and gas recovery. In the presented architecture, a hybrid-boost MMC with a reduced number of semiconductor devices driving a multiphase Induction Machine (IM) is investigated. The stepped output voltage generated by the MMC reduces or eliminates the filtering requirements. Moreover, the boosting capability of the proposed architecture eliminates the need for bulky low-frequency transformers at the converter output terminals. A detailed illustration of the hybrid-boost MMC operation, the expected limitations/constraints, and the voltage balancing technique are presented. A simulation model of the proposed MV hybrid-boost MMC-based five-phase IM drive has been built to investigate the system performance. Finally, a downscaled prototype has been constructed for experimental verification.