Expressions varistors deteriorate

TGE metal oxide varistor identification is a zinc oxide as the main body, add a polycrystalline semiconductor ceramic element more metal oxides, classic electronic ceramics made. Because of its unique grain boundary junction
Structure, at a certain electric field, the grain boundary by a heat conductive conduction electron-emitting instantly converted to electron tunneling conduction, as the voltage increases abruptly decreases its resistance value, having excellent non-linear volt Ante
Sex. So, when there is over-voltage, grain boundaries electron tunneling suppression overvoltage peak growth, absorbing part of the over-voltage energy, and thus play a protective role on the line or equipment.
However, regardless of varistors used in power lines or electrical lines, if the various types of overvoltage occurs frequently, then the varistors will be frequent movement to suppress the release of over-voltage amplitude and to absorb
Surge energy, protection of electrical equipment and components, which will inevitably lead to degradation in performance varistors and even failure.
Varistor failure mode there are three kinds: (1) deterioration of the performance of the leakage current increases, the breakdown voltage decreased significantly until zero; (2) burst, surge energy if overvoltage caused by too much, more than
The chosen varistor metal oxide limit the capacity, the will of ceramic varistor overvoltage occurs when suppressing burst phenomenon; (3) the perforation, especially if the over-voltage spikes high, causing varistors
Ceramic instantaneous electrical breakdown, showing perforation.
Wherein, under the premise of making grade lightning protection, varistor failure mode most of the performance degradation and perforations (ie short circuit), so when you use varistors, must with
Series with a suitable circuit breaker or fuse, to avoid a short circuit caused the accident.
Currently, the popular over-voltage protection is to TGE metal oxide varistor sizing with current limiting, over-current and deterioration warning means organically together internationally, in addition to its over-voltage protection function, but also with
To prevent deterioration of its own, resulting in a short circuit function.