Spark gap

A spark gap of the discharge space between the two conductors (electrodes) in which a gas is present (for example air). Increasing the voltage between the two electrodes on the breakdown voltage, so the resulting electric field causes ionization of the contained in the discharge space gas, it is conductive, and the line is due to the impact ionization within fractions of a microsecond, by a spark (short) closed.

Triggered spark gaps can be ionizing radiation (ultraviolet radiation, X- rays, gamma rays, charged particles).

The flashover voltage of a spark gap decreases by ionizing radiation and moisture. Even a pointed shape of the electrodes lowers the breakdown voltage, and it comes to locally increased field strength and predischarges.

For example, in air and under standard conditions ( atmospheric pressure) per millimeter between the conductors about 3000 volts needed to rollover a spark.

One feature of the radio link is the extinguishing spark gap, this is achieved by subdivisions and a resonant circuit, the spark goes out again quickly after emergence ( see Deletion radio transmitter ).

Arc chutes ( Deionkammern ) on the switching contacts ensure that switching sparks extinguished quickly, thus produced at the electrodes less contact erosion (wear), and the problem of cooling is smaller. Continues to flow a large current through a spark gap, the spark-over developed into an arc.

At spark gaps unwanted flashovers can occur when accumulated in these insects. This can be avoided by using compressed air which is blown by the spark gap.

Applications

In the spark plug in a spark ignition engine is used to ignite the fuel-air mixture.

The bang radio transmitter of Marconi goes back to experiments by Heinrich Hertz and used a radio link for the generation of radio waves. The resulting spark in this arrangement gave the wireless radio transmission the name. Later they developed the (now also obsolete ) quenched gap transmitter, allowing the higher repetition frequencies of sparks. In the Tesla transformer operates in the primary circuit is often called a switching spark gap.

Nitrogen laser and other devices also use a spark gap to generate high-energy, very short current and voltage pulses. Marx generators need to function radio links and possibly also a trigger or switching spark gap, Trigatron. Spark chambers register the fly-through of elementary particles (eg muons ) - it sparks are generated along the flight path of the particles. In the electrical discharge machining material is removed with the help of a very short spark gap in a liquid metal with high accuracy.

Spark gaps were once used as a simple and very coarse surge in the field of insulators of power lines. These spark gaps are formed in the shape of horns at the ends of the insulator and are not to be confused with the similar looking corona rings. The horns are used in the case of a rollover to keep the very hot arc of the insulator removed, thus avoiding damage to the insulator.

However, since the open arc between the horns leads to an uncontrollable ionization of the air in the environment, which is transported by wind and thermal air currents, and because of the occurring in electric power grids high instantaneous power of these powerful discharges may result in additional flashovers on adjacent transmission line parts with subsequent errors lead. To protect against over-voltage overhead lines, therefore, instead of the open horns increasingly encapsulated arrester consisting of varistors or gas discharge tubes, used with better-defined ignition and discharge capacity.

Also on insulators at radiating transmitting masts find spark gaps for overvoltage protection applications. This overvoltage occur especially due to atmospheric discharges - like approaching end thunderstorms - on. However, there occur electric arc services are low, so that it comes through the arc no significant damage to the spark gaps.

The largest spark gaps arise during thunderstorms as lightning between two clouds or between a cloud and the earth.

A special geometric shape of a spark gap represents the Jacob's Ladder