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Control Circuit (control + circuit)
Selected AbstractsNon-superconducting fault current limitersEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2009M. Tarafdar Hagh Abstract This paper proposes the use of non-superconducting DC reactor type fault current limiter (NSFCL) instead of superconducting fault current limiters (SFCLs) which has high cost and technology. Proposed FCL consists of three similar sets, each including a diode bridge and a single non-superconducting DC reactor. The device is connected in series with distribution line and it has almost no effect on the normal system operation. It is not necessary to use a control circuit and it has a simple and cheap power circuit. Design characteristics, analytical analysis and overall transient and steady-state performance of NSFCL in normal and fault conditions are presented in this paper. The comparison between experimental and simulation results indicate good agreements. The results confirm that the power loss of NSFCL is a very small percentage of distribution line power. Also, the system current and load voltage distortions due to using NSFCL is explained and simulated. Copyright © 2008 John Wiley & Sons, Ltd. [source] Dynamic model of one-cycle control for converters operating in continuous and discontinuous conduction modes,INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5 2009N. Femia Abstract In this paper a new dynamic model of one-cycle-controlled converters operating either in continuous or in discontinuous conduction mode (DCM) is introduced. The static and dynamic behaviour is analysed by using sampled-data modelling combined with the small-signal linearization of the average model of the converter's power stage. The proposed model is valid for frequencies up to half the switching frequency and, while the other dynamic models presented in the literature cover continuous conduction mode only, it also gives an accurate prediction of the system's dynamic behaviour in the DCM. The model allows to determine the closed-form expression of the reference-to-output transfer function G of the system, which is a fundamental prerequisite for the design of a conventional output feedback control circuit aimed at improving the dynamic behaviour of the system in response to load variations. In this paper it is also shown that one-cycle control does not work properly in switching converters operating in deep DCM if some specific design constraints are not fulfilled. The theoretical predictions are confirmed by the results of suitable numerical simulations and laboratory experiments on a one-cycle-controlled buck-switching converter. Copyright © 2008 John Wiley & Sons, Ltd. [source] Frequency reconfigurable RF circuits using photoconducting switchesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010D. Draskovic Abstract Designs for a frequency switchable dual-band branch-line coupler and a reconfigurable S-band power amplifier input matching network with photoconducting switches are presented. Frequency switching is achieved by increasing the power of the laser applied to the highly resistive silicon wafer and changing the properties of silicon under optical illumination. The advantages of this approach are high-speed switching, electromagnetic transparency (no interference), and thermal and electrical isolation between the device and the control circuit. A branch-line coupler frequency shift of 35% and 10% has been achieved from all switches off to all switches on in lower (900 MHz) and upper (1800 MHz) frequency bands, respectively. Frequency switchable class AB power amplifier with silicon switch in the input matching circuit has obtained the frequency tuning range of 2.5,3.5 GHz with no significant loss in efficiency and linearity. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] Petri nets based FPGA controller of PDP sustainer with half-voltage energy recovery circuit,ASIAN JOURNAL OF CONTROL, Issue 3 2010Jian-Long Kuo Abstract This paper proposes a FPGA controller design of a driver circuit based Petri nets for the Plasma Display Panel (PDP). In such a driver circuit, complicated control logic is required in the PDP sustainer circuit to implement the sustaining voltage waveform. The control logic has the zero-switching behaviour for the driver circuit to provide better efficiency for the driving circuit. Conventionally, the VHDL programmer does not have a systematic way to program the control logic. Time delay problem of logic components in logic controller may occur under high frequency operation. With the help of the proposed Petri nets approach, the VHDL programming for the PDP driver circuit can be easier in a systematic way. Also, this paper illustrates three types of sustainers with Petri nets based FPGA controller. The basic full-bridge and full-voltage sustainers are used to compare the performance with the proposed half-voltage sustainer. Details of the circuit operation are described. From the experimental results, the performance such as efficiency, luminance, and gamma curve are assessed to show the effectiveness of the proposed half-voltage sustainer. It is believed that the proposed Petri nets based control circuit is very powerful for the practical application of the PDP sustainer circuit. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Tactile sensibility of single-tooth implants and natural teethCLINICAL ORAL IMPLANTS RESEARCH, Issue 2 2007Norbert Enkling Abstract Aim: The purpose of this randomized split-mouth clinical trial was to determine the active tactile sensibility between singe-tooth implants and opposing natural teeth and to compare it with the tactile sensibility of pairs of natural teeth on the contralateral side in the same mouth (intraindividual comparison). Material and Methods: The hypothesis was that the active tactile sensibilities of the implant side and control side are equivalent. Sixty two subjects (n=36 from Bonn, n=26 from Bern) with single-tooth implants (22 anterior and 40 posterior dental implants) were asked to bite on narrow copper foil strips varying in thickness (5,200 ,m) and to decide whether or not they were able to identify a foreign body between their teeth. Active tactile sensibility was defined as the 50% threshold of correct answers estimated by means of the Weibull distribution. Results: The results obtained for the interocclusal perception sensibility differed between subjects far more than they differed between natural teeth and implants in the same individual [implant/natural tooth: 16.7±11.3 ,m (0.6,53.1 ,m); natural tooth/natural tooth: 14.3±10.6 ,m (0.5,68.2 ,m)]. The intraindividual differences only amounted to a mean value of 2.4±9.4 ,m (,15.1 to 27.5 ,m). The result of our statistical calculations showed that the active tactile sensibility of single-tooth implants, both in the anterior and posterior region of the mouth, in combination with a natural opposing tooth is similar to that of pairs of opposing natural teeth (double t -test, equivalence margin: ±8 ,m, P<0.001, power >80%). Hence, the implants could be integrated in the stomatognathic control circuit. [source] Functional connectivity of default mode network components: Correlation, anticorrelation, and causalityHUMAN BRAIN MAPPING, Issue 2 2009Lucina Q. Uddin Abstract The default mode network (DMN), based in ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex (PCC), exhibits higher metabolic activity at rest than during performance of externally oriented cognitive tasks. Recent studies have suggested that competitive relationships between the DMN and various task-positive networks involved in task performance are intrinsically represented in the brain in the form of strong negative correlations (anticorrelations) between spontaneous fluctuations in these networks. Most neuroimaging studies characterize the DMN as a homogenous network, thus few have examined the differential contributions of DMN components to such competitive relationships. Here, we examined functional differentiation within the DMN, with an emphasis on understanding competitive relationships between this and other networks. We used a seed correlation approach on resting-state data to assess differences in functional connectivity between these two regions and their anticorrelated networks. While the positively correlated networks for the vmPFC and PCC seeds largely overlapped, the anticorrelated networks for each showed striking differences. Activity in vmPFC negatively predicted activity in parietal visual spatial and temporal attention networks, whereas activity in PCC negatively predicted activity in prefrontal-based motor control circuits. Granger causality analyses suggest that vmPFC and PCC exert greater influence on their anticorrelated networks than the other way around, suggesting that these two default mode nodes may directly modulate activity in task-positive networks. Thus, the two major nodes comprising the DMN are differentiated with respect to the specific brain systems with which they interact, suggesting greater heterogeneity within this network than is commonly appreciated. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] A new lightning protection system for wind turbines using two ring-shaped electrodesIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2006Yasuda Yoh Member Abstract Wind turbines are often struck by lightning because of their special shape, their tall structure and their being placed in the open air. Besides seriously damaging the blades, lightning results in accidents in which low-voltage and control circuit breakdowns frequently occur in many wind farms worldwide. Although some reports, such as IEC TR61400-24 and NREL SR-500-31115, have indicated a methodology for protection against such accidents, a standard solution to these problems remains to be established. The author, focusing on a method for protection of low-voltage and control circuits in a wind tower, proposed a new lightning protection system with two ring-shaped electrodes attached to the wind turbine. The proposed system has two ring-shaped electrodes of several meters diameter, one vertically attached to the nose cone and the other laterally placed at the top of the wind tower lying just below the nacelle. The pair of rings is arranged with a narrow gap of no more than 1 m in order to avoid mechanical friction during rotation of the blades and the nacelle's circling. When lightning strikes a blade, the current reaches the upper ring from a receptor through a conductive wire. Then, the electric field between the two rings becomes high and finally sparks over and the lightning current flows downwards. The current propagates along the lower ring and the grounding wire, which is arranged outside of the wind tower rather than inside, and is safely led to a grounding electrode placed far enough away from the tower's grounding system. In this paper, the author describes a basic experiment using a 1/100 downsized model, and also discusses the concept behind the present system. The result of the downsized experiment provides evidence of an effective advantage for lightning protection. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Improvement of Hemocompatibility in Centrifugal Blood Pump With Hydrodynamic Bearings and Semi-open Impeller: In Vitro EvaluationARTIFICIAL ORGANS, Issue 10 2009Ryo Kosaka Abstract We have developed a noncontact-type centrifugal blood pump with hydrodynamic bearings and a semi-open impeller for mechanical circulatory assist. The impeller is levitated by an original spiral-groove thrust bearing and a herringbone-groove journal bearing, without any additional displacement-sensing module or additional complex control circuits. The pump was improved by optimizing the groove direction of the spiral-groove thrust bearing and the pull-up magnetic force between the rotor magnet and the stator coil against the impeller. To evaluate hemocompatibility, we conducted a levitation performance test and in vitro hemocompatibility tests by means of a mock-up circulation loop. In the hemolysis test, the normalized index of hemolysis was reduced from 0.721 to 0.0335 g/100 L corresponding to an expansion of the bearing gap from 1.1 to 56.1 µm. In the in vitro antithrombogenic test, blood pumps with a wide thrust bearing gap were effective in preventing thrombus formation. Through in vitro evaluation tests, we confirmed that hemocompatibility was improved by balancing the hydrodynamic fluid dynamics and magnetic forces. 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