OVERVOLTAGES or EXTRAVOLTAGES
The OVERVOLTAGES or EXTRAVOLTAGES are considered among the causes generating damages to the electronic equipments.
They can “enter” into the equipment to be protected mainly through the supply or through any data acquisition sensors, therefore both with high and low voltage.
The OVERVOLTAGES or EXTRAVOLTAGES are generally due to atmospheric events or to wrong operations on the line etc.
The danger of the OVERVOLTAGES or EXTRAVOLTAGES is given by the fact that their amplitude can reach also several kV with a very steep rising edge (in the order of a few ms).
For limiting the effect of the OVERVOLTAGES or EXTRAVOLTAGES it is required a device “cutting down” the overvoltage to a value in such a way to protect the equipment and, at the same time, to dissipate the energy associated with the overvoltage.
Due to the steep rising edge, the protection device must have a trigger time less than the rising time of the voltage to be “cut down”.
EMIREL devices E 484 and E 485 are made up of “gas dischargers” and “varistors” combinations and they are used to protect devices subject to strong OVERVOLTAGES or EXTRAVOLTAGES and having high energy associated with the overvoltages or extravoltages (Ex.: atmospheric discharges, lightnings, wrong operations on the line, etc.).