• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.585-588
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• 2002

The USM uses friction between a mobile part (rotor) and a vibration part(stator), which is different from the principle of the conventional motor based on the interaction of electric and magnetic fields. In this thesis, a flat-type $L_1-B_8$ mode USM was designed and fabricated the characteristics of an ultrasonic vibration. The results of fabricated USM are as follows: (1) In case of ultrasonic motor with elastic-body of stainless, when applied voltage, frequency, pressing force of rotor were 50 [V], 27.9 [kHz], 1.5 [N], 5.0[mN m] respectively, the speed of revolution could be presented up to 0 [cm/s]. (2) In case of ultrasonic motor with elastic-body of brass, when applied voltage, frequency, pressing force of rotor were 50 [V], 21.4 [kHz], 1.5 [N], 1.4[mN m]respectively, the speed of rotor revolution was presented up to 0 [cm/s]. (3) The USM of elastic-body of stainless showing 1.17[%], somewhat low, in the maximum efficiency according to torque was superior to the USM of elastic-body of brass showing 0.34 [%]. The Flat-type $L_1-B_8$ mode USM had characteristics of typical drooping torque-speed, large torque and high speed, and operating in both directions by phase reversal.

• 한국산학기술학회논문지
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• 제18권3호
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• pp.7-13
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• 2017

산업의 발달과 산업구조의 변화로 현대인들이 대부분의 시간을 실내 거주 공간 및 사무실에서 보내고 있음을 고려할 때 쾌적한 실내 공기 환경을 제공하는 것은 매우 중요하다. 실내의 습도제어를 위하여 가습기가 사용된다. 이 중 기화식 가습기는 구조가 간단하고 에너지 소모가 적은 장점이 있다. 가정용 기화식 가습에는 고정식과 로터식의 두 방식이 있다. 본 연구에서는 로터식 가습 소자에 대하여 회전수, 침수 깊이 등의 최적화를 수행하였다. 실험 범위는 유동 면적비 57 ~ 90%, 회전수 0.2 ~ 2.0 rpm, 전방 풍속 0.5 ~ 2.5 m/s이다. 가습량이 최대가 되는 유동 면적비는 70%로 나타났다. 한편 로터의 회전수가 가습량에 미치는 영향은 무시할 만하였다. 하지만 압력손실은 회전수에 따라 증가하였다. 또한 풍속이 증가할수록 가습량과 압력손실은 증가하였다. 본 소자의 경우 시간당 가습량은 0.08 ~ 0.31 kg/hr이다. 또한 실험 결과를 이론 모델의 예측치와 비교하였다.

• Tribology and Lubricants
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• 제36권5호
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• pp.279-289
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• 2020

In this paper, a method is proposed for establishing an approximate prediction model of rotor-dynamics through modal testing. In particular, the proposed method is applicable to systems that cannot be established according to conventional methods owing to the absence of information regarding the dimensions and material of the rotor-bearing system. The proposed method is demonstrated by employing a motor dynamometer driven by a 1 MW class induction motor without dimension and material information. The proposed method comprises a total of seven steps, wherein an initial model is established by incorporating approximate dimensions and material information, and the model is improved on the basis of the natural frequency characteristics of the system. During model improvement, the modification factor is introduced for adjusting the elastic modulus and shear modulus of the system. Analysis of critical speed and imbalance response indicates that the separation margin is 67% and the maximum vibration amplitude is less than the amplitude limit of 0.032 mm under the API 611 standard, which means that the motor dynamometer can stably operate at a rated speed of 1800 rpm. Hence, the obtained results validate the feasibility of the proposed method. Furthermore, for broad usage, it is necessary to accordingly apply and validate the proposed method for various rotor-bearing systems.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.784-791
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• 2000

To improve the uniformity of slurry spreading and to reduce the odor problem, a hose slurry spreader was developed, which spread the slurry near to the surface of the soil. First, the uniformity of slurry spreading was investigated. The best result of 8.1 ％ CV was obtained at the rotor speed of 250 rpm than any other speeds for the swine slurry, which contains 13.6% of dry matter. In case of dairy cattle slurry, which contains 8.2% of dry matter, the uniformity has the best result of CV 7.2% by high rotor speed of 330 rpm. A high speed of rotor has built a sufficient pressure in the distributor and discharged a uniform quantity of slurry through the hoses. Therefore, in practical use one should work with rotor speed over 300 rpm to maximize the uniformity of slurry spreading. Second, odor test was done with the swine slurry. While the conventional spreader shows ∑ value 440, the hose slurry spreader and its combination of disk harrow show ∑ value 258 and 184 respectively. With the air dilution sensual test and a 3-point odor bag, the conventional spreader shows 66.9 or 35.4 point and by the hose slurry spreader is 9.7 or 11.1 point. So, the developed spreader was found to have a greater effect on the reduction of odor problem. Finally, it is recommended to spread certain amount of the slurry for paddy field equivalent to the chemical fertilizer based on the N-content. It means 22 tons of swine slurry per ha. Since most of the livestock farms possess less arable land, a system of linking farms is necessary to utilize the slurry crossover the farms. The cost of slurry utilization including filling, transport spreading and brokerage is 3200-6800 Won/㎥ in accordance with the transport distance.

• Journal of Power Electronics
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• 제14권5호
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• pp.967-979
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• 2014

This paper focuses on speed and current sensor fault detection and isolation (FDI) for induction motor (IM) drives. A new, accurate and high-efficiency FDI approach is proposed so that a system can continue operating with good performance even in the presence of speed sensor faults, current sensor faults or both. The proposed three paralleled adaptive observers are capable of current sensor fault detection and localization. By using observers, the rotor flux and rotor speed can be estimated which allows the system to run under the speed sensorless vector control mode when a speed sensor fault occurs. In order to detect speed sensor faults, a threshold-based scheme is proposed. To verify the feasibility and effectiveness of the proposed FDI strategy, experiments are carried out under different conditions based on a dSPACE DS1104 induction motor drive platform.

• 한국소음진동공학회논문집
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• 제18권10호
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• pp.1065-1072
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• 2008

A HDD adopts a sensorless brushless DC (BLDC) motor as a spindle motor. Because there is no direct sensor measuring rotor position. open loop commutations with inductive sensing are used to increase the rotor speed up to a certain speed where the zero crossings of the back electromotive force (EMF) voltage are measurable. Therefore, successful open loop commutations are necessary for the stable start-up control of the spindle motors. In this paper, the time scale and the number of the open loop commutations are employed for design parameters to guarantee robustness to torque constant variation and initial rotor position. The design results are verified by experiments on a very low current start-up of the spindle motor with various environment. The experimental results show that the design results can decrease the start-up failure rate considerably.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.190-198
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• 2002

In switched reluctance motor(SRM) drive, it is necessary to synchronize the stator phase excitation with the rotor position. Therefore the rotor position information is an essential. Usually optical encoders or resolvers are used to provide the rotor position information. These sensors are expensive and are not suitable for high speed operation. In general, the accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor. But the region of high speed, switching angles are fluctuated back and forth from the preset values, witch are cause by the sampling period of the microprocessor. Therefore, the low cost linear encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper It is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate for the practical low cost SRM drive.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.322-325
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• 1991

An induction type small size electrostatic actor has been fabricated and tested using different rotor dielectric sheet type materials and 3 phase ac various frequencies ans volatages. It's maximum no-load speed was about 2800rpm at the applied voltage of 3030V and frequency of 47Hz for the rotor material of polypropylene sheet. The motor speed was increased linearly by increasing with an applied volatage and frequency, and it also influenced greatly by the electrical properties of rotor dielectric material of relative dielectric constant, resistivity and relaxtion time

• 전기학회논문지
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• 제59권12호
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• pp.2179-2189
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• 2010

This paper deals with analytical techniques for performance evaluation of small scaled wind power generator with outer permanent magnet rotor. In part (1), using transfer relations theorem, magnetic field distribution characteristics by PM and armature reaction field are derived. Moreover, electrical parameters such as back-EMF, inductance and resistance are calculated from the obtained field characteristic equations. The proposed analytical techniques are validated by nonlinear finite element method using commercial software 'Maxwell' and performance experiments of the manufactured generator. In part (2), generating characteristics analysis such as constant speed characteristics and constant resistive load characteristics, and performance evaluation according to variation of wind speed will be accomplished using the derived electrical parameters.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.65-71
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• 2003

In a high speed spindle system it is very important to monitor the state of rotating rotor. Particularly in active control spindle system the position sensor must provide feedback to the control system on the exact position of the rotor. In order to monitor the state of a high speed spindle exactly, high accuracy and wide frequency bandwidth of sensors are important. The focus in this paper is to make a fiber optic sensor for monitoring rotor of magnetic bearing, to design the circuit for detecting optical signal, and to evaluation static and dynamic characteristics of fiber optic sensor.