Electrical breakdown
As the spark plasma a momentary light emitting gas discharge at atmospheric pressure is known. It runs along a thin channel and disappears in charge compensation by itself
Sparks in electrical voltages between two electrical conductors or electrodes by impact ionization, when the gap distance is undershot.
In air at standard conditions (atmospheric pressure ) is approximately 3000 volts are needed to rollover a spark per millimeter between the conductors.
Details
The striking distance, ie the distance between two conductors at below which is taking place at a given voltage between them over ( spark discharge ) depends on:
- The shape of the head - sharp wire ends promote a rollover ( see also field emission )
- Of the humidity and the type of gas - moisture is more likely to rollover, sulfur hexafluoride can prevent flashovers
- Ionizing radiation ( eg, ultraviolet, X-rays and gamma rays, charged particles) promotes a rollover
- With decreasing air pressure, the gap distance increases; this is important for electrical installations at high altitude (mountains, planes, missiles): height fixed electrical installations require larger clearance and creepage distances
- High gas pressure reduces the gap distance (meaning, for example, for the function of ignition systems in petrol engines )
If enough power replenished in a spark discharge, it creates an arc or an arc, see also switching arc: While the electrodes remain cold in a spark discharge essentially evaporate at an arc discharge portions of the conductors or electrodes and there is a metal vapor plasma. If a radio link must very often ignite, threatening local overheating and melting of the material. This can be prevented through a column of divided radio link deletion. The discharge will take place at different locations along the circumference of the discs, the burn through spark erosion. The heat capacity of brass plates cools the spark, so they go out quickly when it falls below a minimum current. For very high power the panels are water-cooled.
Also, thunderstorms are lightning spark discharges.
When opening and closing electrical switch arise switching or breaking sparks or switching arcs. They lead to contact wear and can be suppressed or avoided by additional electrical components (protection diode Boucherot member ).
Spark discharges due to static electricity can destroy electronic components (ESD).
A spark is within a very short time ( microseconds down to few 10 ns) by impact ionization, an electrical connection between two electrodes ago, it, very high currents ( in electrostatic discharges several hundred amperes, with flashes of up to 100 kA ).
Spark discharges Send addition to ultraviolet light and radiation always radio wave pulses. Make strong interference sources ( see electromagnetic compatibility, EMC short ) up to the GHz range dar. first radio wave transmitter worked with spark gaps and gave the radio technology its name. Ignition systems of gasoline engines are therefore suppressed by applying, the rate of current rise is reduced with an in- spark plug or spark plug in the resistor. The brush fire on DC motors is also a spark discharge.
Will spark gaps to generate strong electrical stimulus (eg, nitrogen laser, Tesla transformer ) for ionization, chemical reactions for ignition (piezo lighter, spark plug) and used for overvoltage protection in electronic devices and in energy transfer.
A further application is the spark chamber for the detection of the path of ionizing particles.
- Electromagnetic interference source