Deion chamber
A deionization chamber , also referred to as a deionization chamber , spark extinguishing chamber or arc extinguishing chamber , is a device in electrical power engineering for spark extinction of switching arcs , as they occur when high electrical currents are switched off , typically in the event of an electrical short circuit . The deion chamber is used as a component in line circuit breakers and residual current circuit breakers up to breaking currents of 25 kA .
construction
When switching off high currents, a switching arc occurs between the contacts when the contacts are separated. This arc, formed from ionized air, leads to contact erosion even if the contacts are separated as quickly as possible and must be extinguished or deionized as quickly as possible to avoid consequential damage. If the arc voltage does not fall below the arc voltage, the arc remains.
The deion chamber used consists of several, electrically isolated metal plates made of iron with a copper coating, the so-called deion plates as shown in the figure opposite. The switching contacts are structurally arranged directly in front of the deion chamber, so that when the contact opens, the arc, supported by the thermal lift, runs into the V-shaped area of the deion chamber. The deletion occurs due to two effects:
- The arc is split into partial arcs between the metal plates, each partial arc requiring the full burning voltage, since each partial arc has an anode or cathode drop. Sufficient deionized sheets must be used so that the voltage limit at which the arc extinguishes is no longer reached with the last sheets.
- The segmentation and the good thermal conductivity of the metal platelets remove heat from the arc.
When the alternating voltage is switched off, the arc automatically extinguishes itself due to the periodic zero crossings of the operating voltage. However, the air in the switching path remains conductive and partially ionized for a short period of time, so that without additional quenching equipment such as the deion chamber, the arc would re-ignite even with AC voltage.
Because of the large number of deionization plates required for higher switching voltages, the deionization chamber is preferably used in the area of low- voltage networks at voltages below 1 kV. In the field of high-voltage switching technology , other technologies are used, such as vacuum switches or switches with protective gas in the form of sulfur hexafluoride (SF 6 ) and the self-blowing switch .
An alternative is to extinguish the arc with hard gas .
literature
- Adolf J. Schwab: electrical energy systems . 2nd updated edition. Springer, Berlin et al. 2009, ISBN 978-3-540-92226-1 .