163,736 research outputs found

    Particulate and aerosol detector

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    A device is described for counting aerosols and sorting them according to either size, mass or energy. The component parts are an accelerator, a capacitor sensor and a readout. The accelerator is a means for accelerating the aerosols toward the face of the capacitor sensor with such force that they partially penetrate the capacitor sensor, momentarily discharging it. The readout device is a means for counting the number of discharges of the capacitor sensor and measuring the amplitudes of these different discharges. The aerosols are accelerated by the accelerator in the direction of the metal layer with such force that they penetrate the metal and damage the oxide layers, thereby allowing the electrical charge on the capacitor to discharge through the damaged region. Each incident aerosol initiates a discharge path through the capacitor in such a fashion as to vaporize the conducting path. Once the discharge action is complete, the low resistance path no longer exists between the two capacitor plates and the capacitor is again able to accept a charge. The active area of the capacitor is reduced in size by the damaged area each time a discharge occurs

    A high-efficiency and compact charge pump with charge recycling scheme and finger boost capacitor

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    A 16-phase 8-branch charge pump with finger boost capacitor is proposed to increase the power efficiency. Compared with the standard capacitor, the finger capacitor can significantly reduce the parasitic capacitance. The proposed four-stage charge pump with finger capacitor can achieve 14.2 V output voltage from a 3 V power supply. The finger capacitor can increase the power efficiency of the charge pump to 60.5% and save chip area as well

    A practical approach to switching-loss reduction in a large-capacity static VAr compensator based on voltage-source inverters

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    This paper presents a simple method for reduction of switching and snubbing losses in a large-capacity static VAr compensator (SVC) consisting of multiple three-phase voltage-source square-wave inverters. The proposed method is characterized by a “commutation capacitor” connected in parallel with each switching device. The commutation capacitor allows the SVC to perform zero-voltage switching, and to reduce switching losses. The electric charge stored in the commutation capacitor is not dissipated, but regenerated to the DC-link capacitor. Moreover, a soft-starting method for the SVC is also presented to avoid forming a short circuit across the commutation capacitor during startup. Experimental results obtained from a 10 kVAr laboratory setup are shown to verify the viability of the operating principle of the commutation capacitor </p

    Thermodynamic energy exchange in a moving plate capacitor

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    In this paper we describe an apparent paradox concerning a moving plate capacitor driven by thermal noise from a resistor. The plates are attracted together, but a demon restores the plates of the capacitor to their original position when the voltage across the capacitor is small-hence only small forces are present for the demon to work against. The demon has to work harder than this to avoid the situation of perpetual motion, but the open question is how? This is unsolved, however we explore the concept of a moving plate capacitor by examining the case where it is still excited by thermal noise, but where the restoring force on the capacitor plates is provided by a simple spring rather than some unknown demon. We display simulation results with interesting behavior, particularly where the capacitor plates collide with each other. (c) 2001 American Institute of Physics.B. R. Davis, D. Abbott, and J. M. R. Parrond

    Auxiliary Winding Switching Circuit for Single-Phase Induction Motors

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    The most common practice for starting a single-phase induction motor is to connect a starting capacitor, in series, with the auxiliary winding. Here, the possibility of using an electronic switch in parallel with the starting capacitor, is discussed. This work relates particularly to a switching device for electrically connecting and removing the auxiliary winding and starting capacitor from the single-phase induction motor's circuitry. The starting capacitor with the auxiliary winding are disconnected by electronic means as the motor gains speed hence leaving only the main winding in the motor circuit for normal operation

    Torsional Interaction Studies on a Power System Compensated by SSSC and Fixed Capacitor

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    In this paper, a static synchronous series compensator (SSSC), along with a fixed capacitor, is used to avoid torsional mode instability in a series compensated transmission system. A 48-step harmonic neutralized inverter is used for the realization of the SSSC. The system under consideration is the IEEE first benchmark model on SSR analysis. The system stability is studied both through eigenvalue analysis and EMTDC/PSCAD simulation studies. It is shown that the combination of the SSSC and the fixed capacitor improves the synchronizing power coefficient. The presence of the fixed capacitor ensures increased damping of small signal oscillations. At higher levels of fixed capacitor compensation, a damping controller is required to stabilize the torsional modes of SSR
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