• Journal of Power Electronics
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• 제3권2호
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• pp.99-114
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• 2003

This paper presents a feasible development on a highly accurate quick response adjustable speed drive implementation fur general purpose induction motor which operates on the basis of sensorless slip frequency type vector controlled sine-wave PWM inverter with an automatic tuning machine parameter estimation schemes. In the first place, the sensorless vector control theory on the three-phase voltage source-fed inverter induction motor drive system is developed in slip frequency based vector control principle. In particular, the essential procedure and considerations to measure and estimate the exact stator and rotor circuit parameters of general purpose induction motor are discussed under its operating conditions. The speed regulation characteristics of induction motor operated by the three-phase voltage-fed type current controlled PWM inverter using IGBT's is illustrated and evaluated fur machine parameter variations under the actual conditions of low frequency and high frequency operations for the load torque. In the second place, the variable speed induction motor drive system, employing sensorless vector control scheme which is based on three -phase high frequency carrier PWM inverter with automatic toning estimation schemes of the temperature -dependent and -independent machine circuit parameters, is practically implemented using DSP-based controller. Finally, the dynamic speed response performances for largely changed load torque disturbances as well as steady state speed vs. torque characteristics of this induction motor control implementation are illustrated and discussed from an experimental point of view.

• 대한전자공학회논문지SD
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• 제48권6호
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• pp.25-32
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• 2011

본 논문에서는 휴대기기를 위한 고효율 전류구동방식의 DC-DC 벅 변환기를 제안한다. 제안된 전류구동방식의 DC-DC 컨버터는 파워스위치의 전도손실을 최소화하는 적응형 사구간 제어기법을 적용하여 부하전류에 따라 효율을 2~5%이상 향상시킨다. 설계된 DC-DC 벅 변환기는 0.35${\mu}m$ CMOS공정을 이용하여 칩으로 제작 되었으며, 전체 칩의 크기는 0.97$mm^2$이다. 제작된 칩의 입력전압범위는 2.5V~3.3V이고, 출력전압은 1.8V이며 리플전압은 10mV이하로 나타내고 있다. 최대 500mA의 부하 전류에서 구동할 수 있도록 설계 하였고, 200mA에서 최대 93%의 전력효율을 나타내고 있다.

• Korean Journal of Radiology
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• 제25권2호
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• pp.199-209
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• 2024

Objective: This study aimed to compare therapeutic efficacy and technical outcomes between adjustable electrode (AE) and conventional fixed electrode (FE) for radiofrequency ablation (RFA) of benign thyroid nodules. Materials and Methods: Between 2013 and 2021, RFA was performed on histologically proven benign thyroid nodules. For the AE method, AE length ≥ 1 cm with higher power and < 1 cm with lower power were utilized for ablating feeding vessels and nodules, especially those near anatomical structures, respectively. The therapeutic efficacy (volume reduction rate [VRR], complication rate, and regrowth rate) and technical outcomes (total energy delivery, ablated volume/energy, RFA time, and ablated volume/time) of FE and AE were compared. Continuous parameters were compared using a two-sample t-test or Mann-Whitney U test, and categorical parameters were compared using a chi-squared test or Fisher's exact test. Results: A total of 182 nodules (FE: 92 vs. AE: 90) in 173 patients (mean age ± standard deviation, 47.0 ± 14.7 years; female, 90.8% [157/173]; median follow-up, 726 days [interquartile range, 441-1075 days]) were analyzed. The therapeutic efficacy was comparable, whereas technical outcomes were more favorable for AE. Both electrodes demonstrated comparable overall median VRR (FE: 92.4% vs. AE: 84.9%, P = 0.240) without immediate major complications. Overall regrowth rates were comparable between the two groups (FE: 2.2% [2/90] vs. AE: 1.1% [1/90], P > 0.99). AE demonstrated a shorter median RFA time (FE: 811 vs. AE: 627 seconds, P = 0.009). Both delivered comparable median energy (FE: 42.8 vs. AE: 29.2 kJ, P = 0.069), but AE demonstrated higher median ablated volume/energy and median ablated volume/time (FE: 0.2 vs. AE: 0.3 cc/kJ, P < 0.001; and FE: 0.7 vs. AE: 1.0 cc/min, P < 0.001, respectively). Conclusion: Therapeutic efficacy between FE and AE was comparable. AE demonstrated better technical outcomes than FE in terms of RFA time, ablated volume/energy, and ablated volume/time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.288-290
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• 2006

An efficiency improving method for Uninterruptible Power Supply System(UPS) was developed by using OP-AMP based application circuits such as voltage detection device, current detection device and static switch control device. The efficiency improving algorithm was made by mixing the operating concepts of On-Line type UPS with the operating concepts of Off-Line type UPS. The UPS' inverter does not work if the UPS' output load current is not higher than the low load operating current which is about 0-30(%) of the UPS' output load capacity. The low load operating current is adjustable within the half of the UPS' output load capacity. If the UPS' output load current is rising over than the low load operating current, the UPS' inverter starts working and the inverter output power feeds to the loads of UPS. If UPS' input power breaks out while UPS' inverter does not operate because the load current is low, the inverter starts working within 4(ms) with excessive output voltage which is ${\pm}$8(%) of normal UPS' output voltage. Like these. UPS can continuously feeds power to it's load device and reduce power consumptions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.97-99
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• 2007

This paper presents a fuzzy logical control method to implement an on-line optimum efficiency control for Permanent Magnet Synchronous Motor. This method real-timely adjusts the output voltage of the inverter system to achieve the optimum running efficiency of the whole system. At first, the input power is calculated during the steady state in the process of efficiency optimizing. To exactly estimate the steady state of the system, this section needs check up the speed setting on timely. The second section is to calculate input power of dc-bus. The exact measurement of the voltage and current is the vital point to acquire the input power. The third section is the fuzzy logic control unit, which is the key of the whole drive system. Based on the change of input power of dc-bus and output voltage, the variable of output voltage is gained by the fuzzy logical unit. With the on-line optimizing. the whole system call fulfill the minimum input power of dc-bus on the running state. The experimental result proves that the system applied the adjustable V/f control method and the efficiency-optimizing unit possesses optimum efficiency, and it is a better choice for simple variable speed applications such as fans and pump.

• 전력전자학회논문지
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• 제10권5호
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• pp.501-507
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• 2005

본 연구에서는 유도 전동기의 파워 스펙트럼 확산을 위한 LF2407 DSP기반 하이브리드 랜덤 PWM(HRPWM)을 제안하였다. 제안된 방법은 Lead-Lag 랜덤 비트를 갖는 PRBS (Pseudo-Random Binary Sequence)와 논리적으로 비교를 하기 위한 랜덤 삼각파 캐리어로 구성된다. 또한 DSP에 의하여 랜덤 수 및 PRBS 그리고 3상 기준 정현파를 실시간으로 발생하며, DSP외부의 주파수 변조기 MAX038에 의하여 랜덤 주파수의 캐리어를 발생한다. 본 연구의 타당성 검증을 위하여 제안된 기법을 3상 가변속 구동장치에 적용하였으며, 종전의 방법과 전압 및 전류 그리고 전동기 소음의 파워 스펙트럼을 비교 검토하였다.

• Journal of Power Electronics
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• 제6권4호
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• pp.315-321
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• 2006

Switched Reluctance Motors (SRM) have emerged as viable alternatives to other adjustable speed drives such as vector controlled induction motors (VCIM) and permanent magnet brush-less (PMBL) motors due to their simple construction, ease of control, low inertia and higher operating speeds. However, the indispensability of the rotor position sensor in an SRM for its successful operation increases its cost, apart from causing other problems like decreasing its reliability and inability to operate in adverse environmental conditions. In this paper, a new sensorless control scheme for the SRM is advocated. The required fundamental data is obtained by analyzing the SRM using the Finite Elements (FE) package MAXWELL. The drive is studied in both 'with sensor' and 'sensorless' modes and a comparison of the performances, in both cases, is presented for various operating conditions.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.395-399
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• 2001

In this paper, various reduced parts converter topologies and control strategies for power factor correction and motor control are reviewed and systematic design methodology is developed. From this investigation, the converter topologies could be mainly categorized into cascade type and unified type. The detailed operational principles are examined and the performance comparison is derived to illustrate merits and limitations of the converters. Simulation results are provided to help the better understanding of the theoretical description and several experimental results are presented on prototype induction motor better brush less dc (BLDC) motor drives, along with cascade and unified type converters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.651-654
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• 2004

SRM (switched reluctance motor) provides an excellent adjustable speed and torque characteristics. SRM has the possibility of maintaining full power over a wide speed range. So, many attempts are being done from home appliances to industrial applications. Especially, a traction drive of an SRM is one of a good application for it's DC-series characteristic. However, because of the switching mechanism and reluctance torque, it has some disadvantage of noise and vibration. It is difficult to adopt to an appliance demanding silency. Performance and noise tests with 6/4 and 12/8 SRM were excuted to compare the characteristics.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.206-209
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• 2004

The switched reluctance motor(SRM) drive system provides a good adjustable speed and torque characteristics. SRM has the possibility of maintaining full power over a wide speed range. So, many attempts are being done from home appliances to industrial machinery and tools. Especially, a traction drive of an SRM is one of a good application for it's DC-series characteristic. However, because of the switching mechanism it has some disadvantage of noise and vibration. It is difficult to adopt to an appliance demanding silency. A noise simulation and design of 6/4 and 12/8 SRM was done in order to compare each other.