• Progress in Superconductivity
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• 제13권1호
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• 전력전자학회논문지
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• 제4권1호
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• pp.73-81
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• 1999

본 연구에서는 권선형 유도전동기의 회전자회로에 스위치모드 컨버터를 적용시킨 새로운 슬립전력 회수시스템을 제안하고 이를 분석한다. 제안된 시스템의 해석을 통해 적용된 컨버터의 듀티비에 의해 속도가 제어될 수 있으며, 동시에 기존 시스템의 몇가지 특성을 개선할 수 있음을 보인다. 특히 종래 시스템에서 주된 단점으로 되어 있는 저역률 및 전원전류의 고조파성분을 크게 개선할 수 있을 뿐만 아니라 선형적인 속도조절도 가능하다. 제안된 시스템의 타당성을 보이기 위해 이론 및 실험 결과를 제시하고 이를 설명한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2078-2081
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• 1997

IP speed controller is used as a main controller and it makes the system low overshoot and easy controllability. Load torque is estimated by Kalman filter algorithm and parameter controller is used against a rotor inertia negative variations. Parameter Controller (PC) is equipped with a torque observer implemented by software of a digital signal Processor. PC is a parameter controller which selects a moment of inertia J in responding to a load torque to control the system response.

• Journal of Magnetics
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• 제18권4호
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• pp.443-453
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• 2013

Maglev wind turbine generator (MWTG) technology has been widely studied due to its low loss, low maintenance cost, and high reliability. However, the dynamics of the magnetic bearing system differ fromthe those of the traditional mechanical bearing system. A horizontal axial MWTG supported with a permanent magnetic bearing is designed in this research and the radial forces and the natural frequencies of the rotor system are studied. The results show that the generatorhas a cyclical magnetic forceand an unreasonable bearing stiffness may mean that the rotor system needs to work in the resonance region; the bearing stiffness is the key factor to avoid this problem. This is the main rule of the bearing stiffness design in the MWTG, and this rule can also be used in other maglev permanent magnet motors.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.88-93
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• 2008

The electromagnetic parameters of a permanent magnet synchronous motor (PMSM) such as the open load permanent magnet flux, d axis reactance $X_d$, and q axis reactance $X_q$, are most essential to the performance analysis and optimization design of the motor. Based on the numerical analysis of the 3D electromagnetic field, the three electromagnetic parameters of permanent magnet synchronous motors with U form interior rotor structures are calculated by FEA. The rules of the leakage coefficient and reactance parameters changing with the air gap length, permanent magnet magnetism length, and isolation magnetic bridge dimensions in the rotor are given. The calculated values agree well with the measured values. The FEA results are integrated with the self compiled electromagnetic design program to optimize the prototype motor. The tested performances of the prototype motor prove that the method is suitable for the optimization of motor structure.

• 전력전자학회논문지
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• 제9권4호
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• pp.311-318
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• 2004

최근 각종 산업기기 및 자동화기기에는 회전자가 영구자석으로 구성된 브러시리스 전동기의 사용이 증가하고 있다. 그러나 회전자가 영구자석으로 이루어진 BLDC 전동기의 경우 회전자 위치 판별 센서는 필수 요소이다. 그러나 센서(엔코더, 레졸버등)를 사용할 경우 크기 증가, 비용 상승 등의 원인으로 작용한다. 따라서 본 논문에서는 PM BLDC 전동기의 속도제어를 수행함에 있어 기존의 엔코더와 Hall-IC 3개를 이용하지 않고, 두개를 이용하여 회전자의 위치를 판별함과 동시에 속도 센서를 대신하여 사용할 수 있는 방법을 제안하였다. 그 결과 성능은 동일하고, 구동회로의 크기와 제조 단가를 낮출 수 있는 효과를 얻었다.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1343-1350
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• 2000

The evolutionary structure of tip vortices has been investigated with a two-dimensional LDV system for a plain and a slotted blade, respectively. To analyze the effect of slots which bypasses a part of main stream into the tip face, velocity profiles, vortex sizes, their displacements and turbulence intensities during one revolution of the rotor were measured by the phase averaging process. For the comparison of circumferential velocity components of the plain blade and the slotted blade, the peak values of the slotted blade were lower than those of the plain blade, and axial velocity components of the slotted blade were considerably larger than those of the plain blade. The slotted rotor blade enlarged the core size and made the vortex delayed compared with those of the plain blade at the same wake ages. Turbulence profiles had peaks inside the core radii and decayed gradually in the radial direction of vortex coordinate. Also, using a quasi 3-D LDV measurement technique the budget of turbulence kinetic energy was analyzed in radial direction of the vortex core.

• Journal of Power Electronics
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• 제9권3호
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• pp.343-353
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• 2009

In this paper, a nonlinear controller is proposed for Doubly-Fed Induction Machine (DFIM) drives. The nonlinear controller is designed based on an adaptive backstepping control technique, using a fifth order model of an induction machine in the synchronous d & q axis rotating reference frame, whose d axis coincides with the space voltage vector of the main AC supply, and using the rotor current and stator flux components as state variables. The nonlinear controller can perfectly track the torque reference signal measured in the stator terminals under the condition of unity power factor regulation, in spite of the stator and rotor resistance variations. In order to make the drive system capable of operating in the motoring and generating modes below and above the synchronous speed, two level Space-Vector PWM (SV-PWM) back-to-back voltage source inverters are employed in the rotor circuit. It is confirmed through computer simulation results that the proposed control approach is effective and valid.

• 한국정밀공학회지
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• 제28권5호
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• pp.614-622
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• 2011

An internal lobe pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. In particular, the pump is an essential machine element of an automotive engine to feed lubricant oil. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the rotors: usually the outer one is characterized by lobe with multiple profile(ellipse1, involute and ellipse2) shapes, while the inner rotor profile is determined as conjugate to the other. Also, the design of outer rotor depends on new applications with removing carryover phenomenon. The system generates new lobe profile and calculates automatically the flow rate and flow rate irregularity according to the lobe profile generated. In order to obtain rotor shapes in performance and to find optimize the design parameters, a Taguchi method is proposed in this paper. Results obtained from the analysis enable the designer and manufacturer of oil pump to be more efficient in this field.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.365-368
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• 2003

전북 부안군에 설치된 30kW급 Dual-rotor 풍력발전기의 Main rotor blade를 대상으로 공기역학적 모델링을 수행한 후 각종 바람 상황과 풍속에 따라 변화하는 RPM 상황을 고려하여 전산모의 실험을 수행하였다. 또한 출력성능을 향상시키기 위하여 최대 출력을 계산하고 이를 추종하도록 하는 직접 출력 제어 알고리즘을 제안하였다.