• Title, Summary, Keyword: low speed

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Quality of Fresh Vegetable and Fruit Juice produced with Low-Speed and High-Speed Juicers (저속 압착 방식의 착즙기와 고속 파쇄 방식의 블랜더를 사용한 주스의 품질 변화에 대한 연구)

  • Kim, Youngsung
    • The Korean Journal of Food And Nutrition
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    • v.30 no.3
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    • pp.568-577
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    • 2017
  • Vegetables and fruits contain a great deal of vitamins, minerals, dietary fiber and phytochemicals. Therefore, healthconcious consumer prefer beverage made from fresh fruits and vegetables due to their health benefits. This study was conducted to investigate differences in nutritional composition and sensory characteristics of juices depending on the apparatus used: either a low-speed juicer or high-speed blender. All ingredients could be made into juice without addition of water using the low speed juicer. However, addition of water was necessary to produce juice with the high-speed blender. Phenol and flavonoid content, were higher in juice made with the low-speed juicer than that produced with the high-speed blender and were correlated with DPPH radical scavenging ability. Protease activity of pineapples juices was not significantly different for the two methods, but protease activity of kiwi juice was about 8 times higher in juice made with low-speed juicer than that made with the high-speed blender. SOD activity also tended to be higher in the juice made with low-speed juicer. The concentration of dissolved oxygen in the juice made with high-speed blender was higher than that of juice made with a low-speed juicer and was correlated with color change. In addition, the high-speed blender caused an increase juice temperature, but temperature was not changed during use of the low-speed juicer. The noise level of the low-speed juicer was low, but the high-speed blender had high noise intensity comparable to that of railway or aircraft noise. In the sensory evaluation of juice, juice made with the low-speed juicer was preferred over juice made with the high-speed blender. As a result, the overall quality of the juice produced using the low-speed juicer was superior.

Low Speed Control of Induction Machine by Instantaneous Speed Estimation (순시 속도 추정에 의한 유도 전동기의 저속 운전)

  • Kwon, Bong-Hyun;Hyun, Dong-Seok
    • Proceedings of the KIEE Conference
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    • pp.100-102
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    • 1993
  • This paper proposes a control method of induction machine at a low speed range. When an encoder is used for speed detection, we usually obtain speed information from the increased pulse number. At low speed range, however, we can get only average speed between encoder pulses and it makes speed controller unstable. By using a disturbance observer and torque current, it is possible to estimate accurate speed information. The simulation and experiment show that the stable speed control is performed at a low speed with proposed algorithm.

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Improvement in Control Performance of a Servo System Compensating Bandwidth Variations at Low Speed

  • Ji, Young-Eun;Park, Je-Wook;Hwang, Seon-Hwan;Baek, Kwang-Ryul;Kim, Jang-Mok
    • Journal of Power Electronics
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    • v.10 no.4
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    • pp.382-387
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    • 2010
  • This paper presents a novel design method for determining the PID gains of a speed controller for a servo system compensating variations in bandwidth at a low speed. The variations in bandwidth of a speed controller are measured at a low speed and the relationship between the bandwidth and the damping ratio are verified by determining the location of the closed loop pole. The proposed algorithm uses the z-transform of a plant and speed controller and applies the time-varying sampling method for determining the PID gains of the speed controller at low speed. The magnitude and the phase condition are considered for finding a suitable control gain. The usefulness and effectiveness of the proposed method is demonstrated through experimental results such as low speed control and robust disturbance responses.

A Study on the Neck Injury in Low Speed Rear Impact through the Real Car Test (실차시험을 통한 저속 추돌시 목상해 연구)

  • JO, H.C.;PARK, I.S.
    • Journal of the Korean Society of Mechanical Technology
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    • v.13 no.1
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    • pp.49-56
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    • 2011
  • The neck injury occupies the most of injury that happened by the rear impact car accident. This study was analyzed about influence of the neck injury in low speed rear impact and car crash accident investigation. There is no neck injury in low speed side rear impact. On the other hand, there is initial neck injury symptom of 10 % but no long-term neck injury symptom in low speed offset rear impact. It appeared that the possibility of neck injury in low speed rear impact is low. For the more study about the neck injury, it should be evaluate the effects of the car body structure, frame structure and rear crash pattern.

Influence of Large Change of Specific Speed on the Performance of Very Low Specific Speed Centrifugal Pump (비속도의 큰 변화가 극저비속도 원심펌프의 성능에 미치는 영향)

  • Choi, Young-Do;Kagawa, Shusaku;Kurokawa, Junichi
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.1
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    • pp.40-46
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    • 2006
  • Efficiency of a centrifugal pump is known to drop rapidly with a decrease of specific speed $n_s$. However, below $n_s=60\;[min^{-1},\;m^3/min,\;m]$, the pump characteristics are not yet clear. Therefore, present study is aimed to investigate the influence of large change of specific speed on the performance of a very low specific speed centrifugal pump. Moreover, influence of impeller configuration on the performance of very low specific speed pump is investigated. The results show that very low specific speed can be accomplished by reducing volute throat sectional area using circular spacer. Influence of the spacer's location and configuration in the discharge passage on the pump performance is very small. Best efficiency of very low specific speed centrifugal pump decreases proportionally to the specific speed but the best efficiency decreases on a large scale in the range of $n_s<40$. Influence of impeller configuration on the pump performance and radial thrust of centrifugal pump are considerably small in the range of extremely low specific speed $(n_s=25)$.

A study on Instantaneous Speed Observer for Very Low Speed Drive of Induction Motors (유도전동기의 극저속도 운전을 위한 순시속도 관측기에 관한 연구)

  • Hwang, Lark-Hoon;Na, Seung-Kwon;Jung, Nam-Gil
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.5 no.3
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    • pp.117-126
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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 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.

Influence of Circualr Casing on the Performance of Very Low Specific Speed Centrifugal Pump (원형케이싱이 극저비속도 원심펌프의 성능에 미치는 영향)

  • Choi, Young-Do;Kagawa, Shusaku;Kurokawa, Junichi
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.1
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    • pp.32-39
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    • 2006
  • Recently, according to the trend of small size in scale and high speed in rotation of turbomachinery, very low specific speed centrifugal pump is taking a growing interest because the pump is characterized by high head and low flow rate with convenience of manufacturing and maintenance compared with conventional positive displacement pump. However, the efficiency of the very low specific speed centrifugal pump drops rapidly with the decrease of specific speed. The purpose of this study is nor only to examine the influence of casing type on the performance of centrifugal pump in the range of very low specific speed but also to determine the proper casing type for the improvement of pump performance. The results show that circular casing is suitable for the centrifugal pump in the range of very low specific speed and the influence of impeller configuration on the pump performance is very small. Radial thrust in the circular and volute casings is considerably small in the range of very low specific speed.

A Novel Sensorless Low Speed Vector Control for Synchronous Reluctance Motors Using a Block Pulse Function-Based Parameter Identification

  • Ahmad Ghaderi;Tsuyoshi Hanamoto;Teruo Tsuji
    • Journal of Power Electronics
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    • v.6 no.3
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    • pp.235-244
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    • 2006
  • Recently, speed sensorless vector control for synchronous reluctance motors (SYRMs) has deserved attention because of its advantages. Although rotor angle calculation using flux estimation is a straightforward approach, the DC offset can cause an increasing pure integrator error in this estimator. In addition, this method is affected by parameter fluctuation. In this paper, to control the motor at the low speed region, a modified programmable cascaded low pass filter (MPCPLF) with sensorless online parameter identification based on a block pulse function is proposed. The use of the MPCLPF is suggested because in programmable, cascade low pass filters (PCLPF), which previously have been applied to induction motors, the drift increases vastly wl)en motor speed decreases. Parameter identification is also used because it does not depend on estimation accuracy and can solve parameter fluctuation effects. Thus, sensorless speed control in the low speed region is possible. The experimental system includes a PC-based control with real time Linux and an ALTERA Complex Programmable Logic Device (CPLD), to acquire data from sensors and to send commands to the system. The experimental results show the proposed method performs well, speed and angle estimation are correct. Also, parameter identification and sensorless vector control are achieved at low speed, as well as, as at high speed.

Improvement of Low Speed Characteristics in Induction Motor Drives by Reduced Order Torque Observer (감소차원 토크관측기를 이용한 유도전동기의 저속운전특성 개선)

  • 유영석;윤덕용;홍순찬
    • Proceedings of the KIPE Conference
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    • pp.177-181
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    • 1997
  • In the speed control system of motors using the low resolution rotary encoder, the period of encoder pulse becomes longer than the sampling time for speed control in the range of very low speed. Therefore, it is difficult to obtain accurate speed information. In this paper, the speed estimating method at the very low speed region using reduced order torque observer, which has been widely used, is examined. The results of simulation show that the characteristics of the speed control at the very low speed region is improved by using the reduced order torque observer.

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Performance Characteristic of a Pipe Type Centrifugal Pump (파이프형 원심펌프의 성능특성에 관한 실험적 연구)

  • Yu, HyeonJu;Kang, Shin-Hyoung
    • The KSFM Journal of Fluid Machinery
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    • v.15 no.5
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    • pp.32-36
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    • 2012
  • The positive displacement pump and the regenerative pump are widely used in the range of low specific speed, $n_s{\leq}100$[rpm, m3/min, m]. The positive displacement pump is not suitable for miniaturization and operation in high rotational speed. The regenerative pump has a problem with large leakage flow and low efficiency. While the centrifugal pump has advantages of high efficiency, miniaturization and high rotational speed, efficiency drops sharply with decrease in specific speed. Therefore the purpose of this study is to design a new type of centrifugal pump that has advantages of centrifugal pumps in operation in low specific speed. The name of this new type of pump was called 'Pipe type centrifugal pump', since the flow path through the impeller is simple circular pipe. Due to the simple shape of impeller, the manufacturing process is simple and cost is low. There is strong jet flow at the outlet of the impeller. This jet induces flow path loss, meridional dynamic pressure loss and mixing loss. Large disk friction makes the efficiency be limitted in the range of low specific speed. Even though the loss and the low efficiency, 'Pipe type centrifugal pump' represents stable performance, affordable pressure ratio and efficiency better than that of other low specific speed pumps.