• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.232-234
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• 2002

A Vacuum Circuit Breaker Model for simulation of transient overvoltages was developed by using the PSCAD/EMTDC. The Model includes the power frequency chopping current. Breaker withstand voltage, and quenching capability of High frequency currents. To verify the abilities of the breaker model, the simulation on the Lindmayer's single-phase circuit was carried out. The results show that using the proposed model, the transient overvoltages, current chopping, and multiple reignitions of vacuum breaker are properly reproduced as real phenomena. In further study, virtual chopping current will be incorporated into the model for 3 phase system.

• Journal of Power Electronics
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• v.11 no.4
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• pp.520-526
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• 2011

This paper presents a balanced soft-chopping circuit and a modified PI controller for a high speed 4/2 Switched Reluctance Motor (SRM) with a 16 pulse per revolution encoder. The proposed balanced soft-chopping circuit can supply double the switching frequency in the fixed switching frequency of power devices to reduce current ripple. The modified PI controller uses maximum voltage, back-emf voltage and PI control modes to overcome the over-shoot current due to the time delay effect of current sensing. The maximum voltage mode can supply a fast excitation current with consideration of the hardware time delay. Then the back-emf voltage mode can suppress the current over-shoot with consideration of the feedback signal delay. Finally, the PI control mode can adjust the phase current to a desired value with a fast switching frequency due to the proposed balanced soft-chopping technology.

• Journal of Biomedical Engineering Research
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• v.2 no.1
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• pp.55-64
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• 1981

The important parameters of DC amplifier, which is widely use4 for the medical and engineering fields, are input offset voltage and temperature drift. Chopping amplifier reduces approximately 10% the parameters changing than monolithic operational amplifier. In this study, a chopping amplifier with semiconductor chopper is designed and tested, this chopper is realized by CMOS analog switch and timing circuits. The test results approve that designed amplifier is suitable for precision instrument DC amplifier.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.12
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• pp.106-112
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• 1996

A ZVT (zero voltage transition) converter for SRM (switched reluctance motor) drives is proposed in this study. By adding a ZVT-chopping switch in the front-end, all switches in the machine side converter can be operated without any chopping to regulate phase current. This allows the use of low-cost and slow-switching devices for the machine side converter. The ZVT circuitry allows high frequency operation of th echopping switch, which enhnaces the system dynamcis and phase-current ripples. High efficiency of th eintegrated converter is obtained due to low switching losses.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1210-1212
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• 1994

An amplitude modulation technique for increasing the laser penetration efficiency for metals has been studied. By chopping electro-optically Nd:YAG laser pulse, the threshold energy for reliable hole drilling was decreased significantly and the penetration depth was increased. It was observed that the effect of chopping was optimal at 8-12 kHz with 60% duty cycle. It is believed that this improvement is due to an increase in the vapor recoil pressure and reduced plasma screening.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1013-1015
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• 1993

The switched reluctance motor is excited and controlled by two kinds of excitation; chopped excitation and switched excitation. The former produces additional inverter losses, and onuses drive control to be complicated. The limit of chopping frequency reduces a range of operating speed and torque. This paper examines chopped excitation and switched excitation in a nonlinear switched reluctance motor. The result indicates switched excitation can be satisfactorily applied to the full operating range, and furthermore indicates the improved efficiency.

• the MEAT Journal
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• s.15 spring
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• pp.19-31
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• 1997

• Journal of Fisheries and Marine Sciences Education
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• v.12 no.2
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• pp.142-151
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• 2000

The studies on the electronic control fuel injection system for a DI diesel engine have done for reducing the exhaust emission and improving fuel consumption. The electronic control fuel injection system is classified into a common rail system, a unit injector system and a high pressure injection system. The characteristics of these systems are largely depends on the operating characteristics of its solenoid that have high speed on-off operation. In order to improve these characteristics of fuel injection system, it is necessary to design the optimal shape of solenoid and select the input method of its power source. It was proposed HELENOID, COLENOID, DISOLE, and Multipole Solenoid in the studies of design for the optimal shape of solenoid. The studies on the energizing method, input method for power of solenoid were dealt with the conventional energizing method, the chopping method and the pre-energizing method. In order to find out the high response characteristics of solenoid, it is necessary to test the performance of optimally designed solenoid with a new energizing method. In this paper, the solenoid of multi-pole type with plat armature and its power control unit to control input current by the chopping method designed, and its response tests were performed according to its energizing conditions. As a result, the maximum input current for solenoid was controlled by the period of first stage exciting current and chopping duty ratio of control stage exciting current, and the fastest "on" time was able to get 0.46ms. The conditions of fastest "on" time was 0.3ms for first stage exciting current, 0.16ms for control exciting current and 75% for chopping duty ratio.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.2
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• pp.269-280
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• 1995

저작은 교합과 악운동 뿐만 아리라 근신경계, 고위 중추까지 복합적으로 관여하는 기능적 행위이다. 교합 양상은 다양하게 저작 형태에 영향을 끼치며 저작 효율에도 관여한다. 저작 형태는 다양한 모양을 가지나 두가지 전형적인 군 즉, 전방에서 관찰시 그 양상이 수직적이며 chopping운동을 닮은 군과 저작 형태가 주로 측방으로 이루어지며 grinding을 하는 군으로 나눌 수 있다. 본 연구의 목적은 저작 형태의 치아가 교합접촉 및 저작 효율에 미치는 영향을 고찰해 보고자 하는 것이다. 하악운동궤적기록기를 이용하여 정상교합을 가진 치과대학생중 전형적인 2가지 저작형태를 보이는 각 10명씩을 피검자로 선택하였다. 3가지 하악위 즉, 중심위, 작업측 비작업측에서의 교합접촉을 고무형 교합인기재로 기록하여 천공부의 직경이 1mm이하면 1점, 1-2mm또는 직선상이면 2점, 2mm이상이면 3점으로 평가하여 각 점수의 합으로 좌우 소구치 및 대구치의 접촉 지수를 측정하였다. 저작 효율을 평가하기 위해 땅콩 3g(${\pm}0.01g$)을 20회 저작하게 한 후 3회 입을 헹구어 뱉게 하였다. 체눈 크기가 각 0.425, 0.60, 0.85, 2.0, 4.0인 체에 거른 후 $65^{\circ}C$로 오븐에서 세시간 말려 무게를 측정하고 중심 크기$(M_{50})$과 저작효율치(R)를 계산 비교하여 다음과 같은 결론을 얻었다. 1. Chopping형은 grinding형에 비해 중심위에서 더 넓은 교합접촉을 보였다(P<0.01). 2. Grinding형은 chopping형에 비해 측방위에서 더 넓은 교합접촉을 보였다(P<0.01). 3. Chopping형은 중심크기($(M_{50})$)과 저작효율치(R)로 비교하였을 때 더 좋은 저작 효율을 보였다(P<0.01).

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.2
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• pp.295-301
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• 1992

Eight crop residues : 1, sorghum (Sorqhum bicolor) straw, 2, maize (Zea mays) straw, 3, cotton (Gossypium Sp.) straw, 4, sunflower (Helianthus Sp.) straw, 5, cotton (Gossypium Sp.) seed hulls, 6, groundnut (Archais hypogaea) hulls, 7, maize (Zea mays) cobs, 8, sugarcane (Saccharum officinarum) bagasse and two forest grasses 9, Heteropogan contortus dry grass and 10, Sehima nervosum dry grass were subjected to three physical processing 1, chopping (2-3 cm) 2, grinding (8 mm sieve) and 3, pelleting (10 mm die holes). The processed material was fed ad lib. Along with 250 g of concentrate mixture per head per day to 6 adult local goats and 16 adult Nellore rams in ten digestion experiments and finally assessed the nutritive value of the processed roughages by difference method. Grinding increased bulk density by 32.4 (cotton seed hulls, CSH) to 88.1% (Sehima dry grass) while pelleting of ground material increased bulk density by 53.9 (maize cobs) to 235.8% (maize straw). The average particle size ranged from $584.1/^U$ (sorghum straw) to $1467/^U$ (CSH). Modulus of uniformity ranged from 2:5:3 (sorghum straw) to 7:2:1 (CSH) while modulus of fineness ranged from 3.4 (sorghum straw) to 5.4 (CSH). Molasses absorbability was highest with cotton seed hulls and least with maize cobs. Pelleting increased DM intake of the residues except cotton seed hulls compared to grinding. Grinding of chopped material/unprocessed material increased DM intake on sorghum straw and cotton seed hulls. Sheep consumed more DM compared to goats on all the residues except sorghum and sunflower straws. Pelleting increased nutritive value of all the residues compared to grinding and chopping. However, no difference was observed in the nutritive value due to grinding and chopping. Goats performed better compared to sheep in utilizing the fibrous residues.