Obsah obrázku text, Písmo, snímek obrazovky, řada/pruh Popis byl vytvořen automaticky 5. Arc FB242 Gas discharges: physical mechanisms and applications Obrázok, na ktorom je bezstavovce, modré Automaticky generovaný popis Obrázok, na ktorom je bezstavovce, modré Automaticky generovaný popis • disch1 The emission of electrons from the cathode is governed by the surface temperature Ts,the surface electric field E, and the presence of ions in the cathode region. When the emission is only due to the temperature effect and the surface electric field is low, the emission is said to be thermoelectron and the electron current density JT can be predicted by the Richardson-Dushman equation: Schottky Effect | Electrical4U https://www.electrical4u.com/schottky-effect/ Obrázok, na ktorom je text Automaticky generovaný popis Obrázok, na ktorom je text S.Wang et al.: J. Appl. Phys. 125, 043304 (2019): „Characteristic study of a transient spark driven by a nanosecond pulse power in atmospheric nitrogen using a water cathode“ Obrázok, na ktorom je text Automaticky generovaný popis Arc discharge requires the discharge current higher than several Amps and has negative V/A characteristics: Obrázok, na ktorom je text Automaticky generovaný popis • •Electric arcs are discharges in gases and vapours (vacuum arcs) with currents of more than 1 A and relatively small burning voltages, in general less than 100 V. In contrast to a glow discharge, secondary electron emission is negligible. Typically, the discharge constricts to small footpoints, the cathode spots, leading to energy transfer to the cathode. This causes surface heating to such an extent that thermionic electron emission can cover a part or the whole of the required current. The cathode voltage drop is typically a little less than the ionization potential of the plasma gas. • • •Arc discharge column: -some 99% of the total current is the electron current -some 1000 electrons are emitter per 1 ion incoming to the cathode (it is not the secondary el. emission !!!) -The temperature is typically • 6 000 – 20 000 K so that • the the thermal ionization • can be also significant • (Saha equation) • • • • • • • DOI:10.1088/1757-899X/29/1/012004 The term “arc” is due to the fact that a sufficiently long discharge between the horizontal electrodes has an arc shape, caused by free-convective vertical gas motion. „Gliding Arc“ Obrázok, na ktorom je objekt, zápas Automaticky generovaný popis 500 kV High-voltage disconnect-switch arcing PINCH EFFECT is the tendency of an electric-current channel in a compressible conducting medium to decrease its cross-section under the action of the magnetic field produced by the current. The phenomenon was first described in 1934 by the American scientist W. Bennett with respect to streams of fast charged particles in a gas-discharge plasma. The term “pinch effect” was introduced in 1937 by the British physicist L. Tonks in an investigation of arc discharge. (TOKAMAKs !) https://encyclopedia2.thefreedictionary.com/Pinch+Effect CE517600FG0020 Pinched aluminium can, produced from a pulsed magnetic field created by rapidly discharging 2 kilojoules from a high voltage capacitor bank https://www.plasma-universe.com/pinch/ Tungsten blow-off in response to the ignition of arcing: revival of arcing issue in future fusion devices Shin Kajita 1, Noriyasu Ohno 1, Shuichi Takamura. - ppt download S.A. Grashin, et al. Fusion Engineering and Design 146 (2019) 2100–2104„In a real tokamak conditions the combination of both the heat and particle fluxes is supposed to enhance tungsten damage and erosion. Different mechanisms of plasma-surface interaction can concentrate energy flux on a small surface area. One of such mechanisms could bethe nonambipolar heat flux due to the arcs and sparks.“ Obrázok, na ktorom je hviezda, vonkajší objekt Automaticky generovaný popis Capillary arc discharge is an effective source of high-density plasmas Výsledok vyhľadávania obrázkov pre dopyt capillary plasma electrode discharge Getting the biggest bang out of plasma jets ARC MICRALIGN 677-0872 High Pressure Bent Capillary Mercury Arc Lamp Arc plasma torches High temperature plasma jets up to some 50 000 K Own magnetic field of the arc B is pushing the plasma out from the anode nozzleresulting in the plasma jet Arc plasma cutting https://www.open.edu/openlearn/science-maths-technology/engineering-technology/manupedia/plasma-arc -cutting Arc plasma welding Súvisiaci obrázok Výsledok vyhľadávania obrázkov pre dopyt transferred arc •There are two types of plasma-arc welding process: •° In the transferred-arc method (Fig. a), the workpiece being welded is part of the electrical circuit. The plasma arc transfers from the electrode to the workpiece hence the term transferred. •° In the non transferred method (Fig. b), the arc occurs between the electrode and the nozzle, and the high temperature is carried to the workpiece by the plasma gas. This thermal energy-transfer mechanism is similar to that for an oxy-fuel. plasma arc welding process Hybrid water/argon-stabilized plasma (WSP-H) torch Inst. of Plasma Physics, Prague Obrázok, na ktorom je text Automaticky generovaný popis Enthalpy of WSP-H torch is more than order of magnitude higher than for conventional torches based on gas-stabilization. https://www.wsp-h.com/ Plasma spraying spray Obrázok, na ktorom je text, tmavé, svetlo, osvetlený Automaticky generovaný popis Obrázok, na ktorom je text Automaticky generovaný popis Magnetoplasmadynamic thruster https://en.wikipedia.org/wiki/Magnetoplasmadynamic_thruster Obrázok, na ktorom je text Automaticky generovaný popis Spark discharge is a temporary arc discharge. The spark duration is rastricted by the DC power supply characteristics. Jiskra Obrázok, na ktorom je fialová Automaticky generovaný popis Applications: Spark gaps – HV switching: SparkGap T Huiskamp: Plasma Sources Sci. Technol. 29 (2020) 023002 „Spark-gap switches exist in many different configurations, but all rely on a conducting channel being formed in an electrode system. In its simplest form, a spark gap consists of two opposing electrodes placed in a gas (or liquid) medium. Once the voltage across the electrodes exceeds a certain threshold voltage a discharge is initiated in the gap. If this results in the complete breakdown of the gap a conducting channel is formed and the spark-gap switch is switched ‘on’. Once the conducting channel is quenched (when the voltage across the electrodes and the current through the channel fall below a certain threshold) the sparkgap switch is switched ‘off’ again. The advantage of such switches is that they are capable of switching (extremely) high voltages at (extremely) high currents and in special configurations with subnanosecond rise times. The disadvantage of the spark gap is that it typically requires maintenance (the electrodes erode), that an auxiliary gas- or liquid flushing and filtering system is required for high power operation and that the achievable repetition rates are limited because the medium in the gap has to recover before it can hold off the full voltage again.“ T Huiskamp: Plasma Sources Sci. Technol. 29 (2020) 023002 „Spark-gap switches exist in many different configurations, but all rely on a conducting channel being formed in an electrode system. In its simplest form, a spark gap consists of two opposing electrodes placed in a gas (or liquid) medium. Once the voltage across the electrodes exceeds a certain threshold voltage a discharge is initiated in the gap. If this results in the complete breakdown of the gap a conducting channel is formed and the spark-gap switch is switched ‘on’. Once the conducting channel is quenched (when the voltage across the electrodes and the current through the channel fall below a certain threshold) the sparkgap switch is switched ‘off’ again. The advantage of such switches is that they are capable of switching (extremely) high voltages at (extremely) high currents and in special configurations with subnanosecond rise times. The disadvantage of the spark gap is that it typically requires maintenance (the electrodes erode), that an auxiliary gas- or liquid flushing and filtering system is required for high power operation and that the achievable repetition rates are limited because the medium in the gap has to recover before it can hold off the full voltage again.“ Also sub-nanosecond switching time for special radars High-pressure hydrogen-filled Saprk gap: 0.5 mm/0.1 ns =5 . 106 m/s Light velocity = 300 . 106 m/s Overvoltage protection Circuit protection: Miniature spark gaps spark-2.gif (40724 bytes) The lightning arrester protects the electrical equipment from lightning. It is placed very near to the equipment and when the lightning occurs the arrester diverts the high voltage wave of lightning to the ground https://circuitglobe.com/types-of-lightning-arresters.html Obrázok, na ktorom je text, hodinky Automaticky generovaný popis Obrázok, na ktorom je text, vonkajšie Automaticky generovaný popis Obrázok, na ktorom je činka Automaticky generovaný popis Textové pole: .: .: trigatron A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine: https://en.wikipedia.org/wiki/Spark_plug A trigatron is a type of triggerable spark gap switch designed for high current and high voltage (usually 10–100 kV and 20–100 kA, though devices in the mega-ampere range exist as well). It has very simple construction and in many cases is the lowest cost high energy switching option. A trigatron has three electrodes. The heavy main electrodes are for the high current switching path, and a smaller third electrode serves as the trigger. During normal operation, the voltage between the main electrodes is somewhat lower than the breakdown voltage corresponding to their distance and the dielectric between them (usually air, argon-oxygen, nitrogen, hydrogen, or sulfur hexafluoride). To switch the device, a high-voltage pulse is delivered to the triggering electrode. This ionizes the medium between it and one of the main electrodes, creating a spark which shortens the thickness of non-ionized medium between the electrodes. https://en.wikipedia.org/wiki/Trigatron Obrázok, na ktorom je kovový riad, skrutka, svetlo Automaticky generovaný popis Is it the Townsend mechanism ??? Spark discharge generating shock waves in liquids – sonars, lithotryptors, etc. Lithortriptor Plazmová elektrolytická oxidácia (Vytváranie odolných oxidových vrstiev na povrchoch kovov hlavne Al, Mg – medicínske aplikácie) Obrázok, na ktorom je voda, obloha, vonkajšie, čln Automaticky generovaný popis Plasma electrolytic oxidation - TEKNIKER https://sfb1316.rub.de/index.php?option=com_chronoforms5&chronoform=CRCProjektListPublicView&Projek tID=14&TitleString=Project%20B5 https://www.google.com/search?q=plasma+electrolytic+oxidation&safe=active&sxsrf=ALeKk01PIKpWoJ0mFy0 rtwKg7iaGIG-MsA:1615186870031&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjL9Yj9j6DvAhW-wAIHHZJYBQIQ_AUoAX oECAcQAw&biw=1448&bih=762#imgrc=uKz7Rbq2Rdi9hM https://blog.keronite.com/what-is-plasma-electrolytic-oxidation-article Obrázok, na ktorom je modré Automaticky generovaný popis Electrical Discharge Maschining