A varistor is usually a type of resistor using a substantially non-ohmic current-voltage characteristic. The identify is usually a portmanteau of variable resistor*, that is deceptive considering that it is actually not continually user-variable like a potentiometer or rheostat, and is not a resistor but the reality is a capacitor. Varistors are often utilised to safeguard circuits towards extreme voltage by acting like a spark gap. By far the most common type of varistor will be the metal oxide varistor, or MOV. This contains a mass of zinc oxide grains, in a matrix of other metal oxides, sandwiched between two metal plates (the electrodes). The boundary between every single grain and its neighbour types a diode junction, which allows current to movement in only 1 course. The mass of randomly oriented grains is electrically equivalent to your network of back-to-back diode pairs, every single pair in parallel with quite a few other pairs. When a tiny or moderate voltage is applied across the electrodes, only a very small current flows, triggers by reverse leakage via the diode junctions. When a huge voltage is applied, the diode junctions break down for the reason that with the avalanche impact, plus a huge current flows. The result of this behaviour is usually a extremely nonlinear current-voltage characteristic, during which the MOV features a high resistance at minimal voltages plus a minimal resistance at high voltages.When the measurement with the transient pulse (often measured in joules) is also high, the device may perhaps melt, or otherwise be ruined. As an example, a close by lightning strike may perhaps forever harm a varistor. Necessary variables for varistors are response time (how lengthy it will take the varistor to interrupt down), maximum current plus a well-defined breakdown voltage. When utilised in communications lines (which include telephone lines utilised for modems), high capacitance is unwanted considering that it absorbs high frequency signals, therefore decreasing the readily available bandwidth with the line becoming safeguarded.

A metal oxide varistor, or MOV, is usually a voltage dependent, nonlinear device that provides excellent transient voltage suppression. When exposed to high transient voltage, the metal oxide varistor clamps voltage to your secure degree. A metal oxide varistor absorbs potentially harmful energy and dissipates it as heat, therefore defending susceptible circuit components and preventing system harm. Littelfuse metal oxide varistor products are produced primarily of zinc oxide with tiny quantities of bismuth, cobalt, manganese, as well as other metal oxides. They are able to be connected in parallel for increased energy-handling abilities. MOVs may also be connected in series to deliver greater voltage ratings or to deliver voltage rating between the standard

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