The Applications of varistor metal oxide

To protect telecommunication lines, transient suppression devices such as 3 mil carbon blocks (IEEE C62.32), ultra-low capacitance varistor metal oxide , and avalanche diodes are used. For higher frequencies, such as radio communication equipment, a gas discharge tube (GDT) may be utilized.[citation needed] A typical surge protector power strip is built using xatge MOV . Low-cost versions may use only one varistor, from the hot (live, active) to the neutral conductor. A better protector contains at least three varistors; one across each of the three pairs of conductors. In the United States, a power strip protector should have an Underwriters Laboratories (UL) 1449 3rd edition approval so that catastrophic MOV failure does not create a fire hazard.

MOV Block and metal oxide varistor application

In general, the primary case of varistor breakdown is localized heating caused as an effect of thermal runaway. metal oxide varistor application is to a lack of conformity in individual grain-boundary junctions, which leads to the failure of dominant current paths under thermal stress. If the energy in a transient pulse (normally measured in joules)MOV Block is too high, the device may melt, burn, vaporize, or otherwise be damaged or destroyed. This (catastrophic) failure occurs when "Absolute Maximum Ratings" in manufacturer's data-sheet are significantly exceeded.

XAGET Metal oxide arrester features

high performance movs blocks varistor valve main ingredient is zinc oxide, zinc oxide varistor has a very excellent nonlinear characteristics. Under normal operating voltage of the resistance value is high, in fact, equivalent to an insulator, and over-voltage action, the resistance of the resistor is very small, residual pressure is very low. But under normal operating voltage, since the valve frequency voltage is applied to long-term exposure arising from deterioration caused by changes in resistance characteristics, resulting in increased flow through the valve leakage current. The resistive component of the current sharp increase in temperature will rise valves on thermal collapse, severe, or even cause explosion? AC and DC High Performance MOV . In accordance with the provisions of rules 1, XAGET Metal oxide arrester total of six test items, namely (1) Insulation resistance (2) leakage current DC U1mA and 0.75U1mA under (3) AC operation voltage leakage current (4) Power frequency frequency reference voltage (5) Base insulation resistance (6) Check discharge counter action case reference current.

MOV on the proper use of distribution transformers

Metal oxide arrester ?during normal operation and distribution transformers in parallel, the terminating line, the lower end of the ground. The pressure generated when the three parts? MOV for Counter When the line overvoltage occurs, this time over-voltage distribution transformer will be subjected by lightning, leads and grounding devices drop, known as residual pressure. In this three-part over voltage,?lightning arrester?residual pressure on its own performance related to its residual voltage value is constant. Residual voltage on the grounding device can be connected to the grounding deflectors distribution transformer housing, then connected to the grounding device and how to eliminate them. And how to reduce the residual voltage of the leads has become the key to the protection of distribution transformers.

Lead impedance and current frequency through, the higher the frequency, the inductance of the wire, the stronger the greater impedance. From U = IR shows that to reduce the residual pressure on the lead, you have to narrow the lead impedance, and possible ways to reduce the lead impedance is to shorten the distance between the arrester from the distribution transformer to reduce the lead impedance, lower lead drop, so arresters should be installed in a more appropriate distribution transformer near point distance.

Advantages and characteristics of the metal oxide surge arresters

MOVMetal oxide arrester is used to protect the transmission and distribution equipment, insulation against over-voltage protection of electrical hazards is important, it has a fast response, voltage characteristic flat, stable performance,Flow capacity, residual voltage, long life, simple structure, it is widely used in power generation,Transmission, substation, distribution and other systems. Composite coat metal oxide surge arresters is silicone rubber
Composite materials make coats, and traditional porcelain jacket Surge arrester , compared with a small size, light weight, rugged, stain resistance, proof performance and so on.

MOA varistor valve main ingredient is zinc oxide, Metal Oxide Varistors (MOV) has extremely excellent non-linear characteristics. Under normal operating voltage of the resistance value is high, in fact, equivalent to an insulator, and over-voltage action, the resistance of the resistor is very small, residual pressure is very low. But under normal operating voltage, since the valve frequency voltage is applied to long-term exposure arising from deterioration caused by changes in resistance characteristics, resulting in increased flow through the valve leakage current. The resistive component of the current sharp increase in temperature will rise valves on thermal collapse, severe, or even cause explosion arrester. In accordance with the provisions of rules 1, MOA total of six test items, namely (1) Insulation resistance (2) leakage current DC U1mA and 0.75U1mA under (3) AC operation voltage leakage current (4) Power frequency frequency reference voltage (5) Base insulation resistance (6) Check discharge counter action case reference current.

Electrical characteristics

A varistor metal oxide remains non-conductive as a shunt-mode device during normal operation when the voltage across it remains well below its "clamping voltage", thus varistors are typically used for suppressing line voltage surges. However, a polymer arrester may not be able to successfully limit a very large surge from an event like a lightning strike where the energy involved is many orders of magnitude greater than it can handle. Follow-through current resulting from a strike may generate excessive current that completely destroys the varistor.

Lesser surges still degrade it, however. Degradation is defined by manufacturer's life-expectancy charts that relate current, time and number of transient pulses. The main parameter affecting varistor life expectancy is its energy (Joule) rating. As the energy rating increases, its life expectancy typically increases exponentially, the number of transient pulses that it can accommodate increases and the "clamping voltage" it provides during each transient decreases. The probability of catastrophic failure can be reduced by increasing the rating, either by using a single varistor of higher rating or by connecting more devices in parallel. A varistor is typically deemed to be fully degraded when its "clamping voltage" has changed by 10%. In this condition it is not visibly damaged and it remains functional (no catastrophic failure).

The Limitations of metal oxide varistors application

A metal oxide varistors application inside a TVSS device does not provide equipment with complete power protection. In particular, a MOV device provides no protection for the connected equipment from sustained over-voltages that may result in damage to that equipment as well as to the protector device. Other sustained and harmful overvoltages may be lower and therefore ignored by a MOV device.
A varistor provides no equipment protection from inrush current surges (during equipment startup), from overcurrent (created by a short circuit), or from mov varistor (also known as a brownout); it neither senses nor affects such events. Susceptibility of electronic equipment to these other power disturbances is defined by other aspects of the system design, either inside the equipment itself or externally by means such as a UPS, a voltage regulator or a surge protector with built-in overvoltage protection (which typically consists of a voltage-sensing circuit and a relay for disconnecting the AC input when the voltage reaches a danger threshold).