Blow magnet
A blow magnet is a permanent or electromagnet that is used to lengthen the switching arc between contacts of a switch or relay by the Lorentz force acting on the arc and thus to extinguish it more quickly.
functionality
A magnet is arranged in the immediate vicinity of the switching contacts , the north-south axis of which is essentially transverse to the connecting line of the contacts. If the switching contacts are opened, a switching arc forms at higher direct currents, which leads to rapid wear of the contacts. Due to the presence of the external magnetic field, however, the Lorentz force acts on the arc, so that it is pushed away from the magnet ("blown") and thus extended.
The longer arc extinguishes faster because it cools down faster due to the larger surface and the ionized air loses its conductivity more quickly. The use of blow magnets is particularly useful in direct current applications , since the tendency to form arcs is greater here than with alternating current .
Another application is the blow magnet in carbon arc lamps, e.g. B. from older film projectors. The blow magnet is used here to deflect the rising flame of the arc, which consists of plasma (ionized gas) and can therefore be influenced by a magnetic field, away from the concave mirror of the arc lamp and thus to avoid damage to the mirror due to excessive heating in the upper area.
swell
- Hans Sauer : "Relais-Lexikon", 2nd edition, Hüthing-Verlag, Heidelberg 1985, ISBN 3-7785-0943-8 , p. 35
- Data sheet for the JC relay type from Panasonic online (accessed February 15, 2011; PDF; 1.9 MB)