Metal Oxide Varistors (MOV)

While an Metal Oxide Varistors (MOV) is designed to conduct significant power for very short durations (about 8 to 20 microseconds), such as caused by lightning strikes, it typically does not have the capacity to conduct sustained energy. Under normal utility voltage conditions, this is not a problem. However, certain types of faults on the utility power grid can result in sustained over-voltage conditions. Examples include a loss of a neutral conductor or shorted lines on the high voltage system. Application of sustained over-voltage to a mov metal oxide varistor can cause high dissipation, potentially resulting in the MOV device catching fire. The National Fire Protection Association (NFPA) has documented many cases of catastrophic fires that have been caused by MOV devices in surge suppressors, and has issued bulletins on the issue.

A 130 volt, 150 J MOV that has undergone catastrophic failure, apparently as a result of a lightning strike, showing evidence of heat and smoke. The 3 amp fast-blow fuse immediately in front of the varistor blew during the same event.
A series connected thermal fuse is one solution to catastrophic MOV failure. Varistors with internal thermal protection are also available.
There are several issues to be noted regarding behavior of transient voltage surge suppressors (TVSS) incorporating MOVs under over-voltage conditions. Depending on the level of conducted current, dissipated heat may be insufficient to cause failure, but may degrade the MOV device and reduce its life expectancy. If excessive current is conducted by a MOV, it may fail catastrophically, keeping the load connected, but now without any surge protection. A user may have no indication when the surge suppressor has failed. Under the right conditions of over-voltage and line impedance, it may be possible to cause the MOV to burst into flames,[5] the root cause of many fires[6] and the main reason for NFPA’s concern resulting in UL1449 in 1986 and subsequent revisions in 1998 and 2009. Properly designed TVSS devices must not fail catastrophically, resulting in the opening of a thermal fuse or something equivalent that only disconnects MOV devices.

The Specifications of metal oxide varistor application

MOVs are specified according to the voltage range that they can tolerate without damage. Other important parameters are the metal oxide varistor application energy rating in joules, operating voltage, response time, maximum current, and breakdown (clamping) voltage. Energy rating is often defined using standardized transients such as 8/20 microseconds or 10/1000 microseconds, where 8 microseconds is the transient's front time and 20 microseconds is the time to half value.
Response time
The response time of the varistors is not standardized. The sub-nanosecond MOV response claim is based on the material's intrinsic response time, but will be slowed down by other factors such as the inductance of component leads and the mounting method. That response time is also qualified as insignificant when compared to a transient having an 8 μs rise-time, thereby allowing ample time for the device to slowly turn-on. When subjected to a very fast, <1 ns rise-time transient, response times for the MOV are in the 40–60 ns range.
Capacitance

Typical capacitance for consumer-sized (7–20 mm diameter) varistors are in the range of 100–1,000 pF. Smaller, lower-capacitance varistors are available with capacitance of ~1 pF for microelectronic protection, such as in cellular phones. These low-capacitance varistors are, however, unable to withstand large surge currents simply due to their compact PCB-mount size.

The Applications of High voltage varistor

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.

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.

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).

Metal Oxide Varistors (MOV)

Metal Oxide Varistors (MOV) current-voltage characteristics for zinc oxide (ZnO) and silicon carbide (SiC) devices
The most common type of varistor is the metal-oxide varistor (MOV). This type contains a ceramic mass of zinc oxide grains, in a matrix of other metal oxides (such as small amounts of bismuth, cobalt, manganese) sandwiched between two metal plates (the electrodes). The boundary between each grain and its neighbour forms a diode junction,Porcelain housed arrester allows current to flow in only one direction.

The mass of randomly oriented grains is electrically equivalent to a network of back-to-back diode pairs, each pair in parallel with many other pairs. When a small or moderate voltage is applied across the electrodes, only a tiny current flows, caused by reverse leakage through the diode junctions. When a large voltage is applied, the diode junction breaks down due to a combination of thermionic emission and electron tunneling, and a large current flows. The result of this behaviour is a highly nonlinear current-voltage characteristic, in which the MOV has a high resistance at low voltages and a low resistance at high voltages.

Traditional Metal oxide varistors schematic symbol

Traditional Metal oxide varistors schematic symbol. It expresses the diode-like behavior in both directions of current flow.
Modern varistor schematic symbol.
A metal oxide varistors application is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. In contrast to a diode however, it has the same characteristic for both directions of traversing current. At low voltage it has a high electrical resistance which decreases as the voltage is raised.

Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltages. When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered.
The development of the varistor, in the form of a new type of rectifier (copper oxide), originated in the work by L.O. Grondahl and P.H. Geiger in 1927. The name varistor is a portmanteau of varying resistor. The term is only used for non-ohmic varying resistors. Variable resistors, such as the potentiometer and the rheostat, have ohmic characteristics.

the metal oxide varistors application Limitations

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).

Comparison to other transient suppressors
Another method for suppressing voltage spikes is the transient-voltage-suppression diode (TVS). Although diodes do not have as much capacity to conduct large surges as MOVs, diodes are not degraded by smaller surges and can be implemented with a lower "clamping voltage". MOVs degrade from repeated exposure to surges and generally have a higher "clamping voltage" so that leakage does not degrade the MOV. Both types are available over a wide range of voltages. MOVs tend to be more suitable for higher voltages, because they can conduct the higher associated energies at less cost.
Another type of transient suppressor is the gas-tube suppressor. This is a type of spark gap that may use air or an inert gas mixture and often, a small amount of radioactive material such as Ni-63, to provide a more consistent breakdown voltage and reduce response time. Unfortunately, these devices may have higher breakdown voltages and longer response times than varistors. However, they can handle significantly higher fault currents and withstand multiple high-voltage hits (for example, from lightning) without significant degradation.
Multi-layer varistor
Multi-layer varistor (MLV) devices provide electrostatic discharge protection to electronic circuits from low to medium energy transients in sensitive equipment operating at 0-120 volts dc. They have peak current ratings from about 20 to 500 amperes, and peak energy ratings from 0.05 to 2.5 joules.ratings from 0.05 to 2.5 joules.

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.

characteristics for Metal Oxide Varistors (MOV)

Metal Oxide Varistors (MOV) current-voltage characteristics for zinc oxide (ZnO) and silicon carbide (SiC) devices
The most common type of varistor is the metal-oxide varistor (MOV). This type contains a ceramic mass of zinc oxide grains, in a matrix of other metal oxides (such as small amounts of bismuth, cobalt, manganese) sandwiched between two metal plates (the electrodes). The boundary between each grain and its neighbour forms a diode junction, Porcelain housed arrester allows current to flow in only one direction.

The mass of randomly oriented grains is electrically equivalent to a network of back-to-back diode pairs, each pair in parallel with many other pairs. When a small or moderate voltage is applied across the electrodes, only a tiny current flows, caused by reverse leakage through the diode junctions. When a large voltage is applied, the diode junction breaks down due to a combination of thermionic emission and electron tunneling, and a large current flows. The result of this behaviour is a highly nonlinear current-voltage characteristic, in which the MOV has a high resistance at low voltages and a low resistance at high voltages.

XATGE ZnO Blocks with MOV glasses

TGE offers a selection of glasses suitable for use as insulating coatings on Metal Oxide Varistors (ZnO “blocks”). TGE offers powders sized for wet application by dipping, rolling or spraying as well as application by dry electrostatic techniques. Typical firing temperatures are 550°C, resulting in pore-free insulating coatings of suitable toughness to withstand potential damage due to lapping of the block ends prior to metallization. Along with PbO-containing glass options, lead-free versions are also available. If lead-free MOV glasses are of interest, ask for our industrial evaluation report for TGE Glass V1467. Our glasses are melted in platinum lined vessels ensuring consistency of physical properties and preventing unwanted impurities. Glass powders are custom milled to your particle size specifications and can be co-milled with additives to increase surface roughness for handling purposes.

Being an ISO 9001-2008 accredited manufacturer and exporter in the market, we put froth a dependable, durable and remarkable range of  ZnO Blocks. In addition to this, our widely appreciated range is made keeping in mind the exact requirements of the industry. As an outcome, it is extensively in demand nowadays. Besides, by using authentic raw material, we gain appreciation for ZnO Blocks from the masses. As per the requirements of the domain, we deliver the product right on time. 

Zinc Oxide blocks

Nano-block body,ZnO varistor refined grains make the material easy to cause transgranular fracture, will help improve the toughness; grain refinement contributes to slip between the grains, the material has plastic behavior; grain refinement the strength of the ceramic material can also greatly increased [6,7]. Currently nano Sintering more are ZrO2, AI2O3, TiO2 [8,9]. Semiconductor nano-ZnO low-density bulk impedance spectroscopy has been reported [10]. But during sintering of nano Zinc Oxide blocks nanocrystals growth it has not been reported. Studied law during sintering grain growth of ZnO 20nm average particle size of paper as the raw material, the application of grain growth phenomenological theory of kinetic equations to determine the index of grain growth kinetics and the apparent activation energy, and with the rough sintered polycrystalline material was compared, we discussed the mechanism of nano xatge MOV sintered. It laid the foundation for the sintering and application of semiconductor material nanometer ZnO.

ZnO blocks

TGE Metal Oxide Varistors(MOV) ceramic because of its non-linear current-voltage characteristics (and non-linear coefficient is the highest of all semiconductor materials) are widely used in electronic devices [1-5]. ZnO varistors are typically the grain size, grain boundary structure control their macroscopic properties of materials. ZnO grain size and the number of grain boundary layer directly affects the breakdown voltage level. In addition, many other properties are also dependent on the polycrystalline ceramic its microstructure. In recent years, sintering and grain growth of ZnO based ceramics have been many reports of research [1-5]. People around the crystal densification and control of the sintered body sintered body grow a lot of research. According to reports, doped ZnO nano-ZnO Resistors coarse grain has a higher breakdown voltage, the greater the nonlinearity coefficient, low leakage current. And said performance increases with the amount of nano-Zinc Oxide discs [3]. Nano-sintering is the second after the emergence of nanomaterials developed a new sintering technology. The so-called nano-sintering, is to use nano-powder sintering under certain conditions, the microstructure of the phase of the nano-phase materials. Nano-sintering with the conventional sintering coarse grain compared to: (1) low sintering temperature; the nano-powder small size, high surface energy, compressed into a block material after the interface has a high energy, high in sintering interface can become the driving atomic motion force, is conducive to the interface holes shrink, annihilation vacancy clusters, thus enabling the sintering temperature is lowered.

ZnO varistor

In the preparation of nanomaterials and nano-structure, there are many people in different ways.metal oxide varistor theory These methods may be divided according to the state of the reaction medium during the preparation of two categories: solution-based liquid phase reaction of gas phase reaction based on gas phase process. Growth by gas inorganic nano materials and nano-bodies have VLS mechanism main mechanism, VS mechanism, ZnO Resistors growth (OAG) mechanism, SLS mechanism. There is now a zinc oxide fine synthesis of nanostructures with different morphologies are pulsed laser deposition (PLD), chemical vapor deposition (CVD), metal organic chemical vapor deposition (MOCVD), chemical transport method (CTM),overvoltage arrester thermal evaporation, carbothermal reduction. Solvothermal, hydrothermal method.

Promotional Zinc Oxide Disc

In recent years, nano-materials due to its quantum size effect and macroscopic quantum tunneling, etc. ZnO varistorexhibit special optical, electrical, magnetic and catalytic properties, aroused great interest. After the zinc oxide and zinc sulfide nano materials, no doubt given on the basis of the original features of its range of new features, it will help to improve the material performance and functionality. In recent years, studies have shown that Zinc Oxide blocks and zinc sulfide nano-materials with ordinary zinc oxide and zinc sulfide compared to the bulk material, the mechanical properties, high temperature resistance, luminescence, catalysis and many other aspects have improved significantly. Zinc Oxide discsStudy on preparation and performance of materials science has become a very active area.

Zinc oxide varistors Features

TGE AC and DC High Performance MOV are widely used in electronic circuits, transient voltage surge protection because of the power supply system may harm the circuit. Varistor is generally used in parallel with the circuit when the voltage across the resistor changes rapidly, resistance short circuit current fuse blows, play a protective role. varistor metal oxide in the circuit, commonly used in the power supply voltage protection and regulation. Decrease the resistance of the TGE metal oxide varistor identification will be shunt currents, to protect against excessive transient voltage damage or interference.

Parallel applications of zinc oxide varistor

TGE metal oxide varistors application is a voltage limiting protection devices. Nonlinear characteristics of the use of zinc oxide varistors, when an overvoltage occurs between the two poles of the varistor, the varistor voltage can be clamped to a relatively fixed voltage value, in order to achieve protection of the post-stage circuit. Varistor TVS diode can be used instead tvs tube, a combination Zener diode and a capacitor.
Varistor circuit IC can be protected and other equipment, to prevent electrostatic discharge, surges and other transient current (such as lightning, etc.) and cause damage to them. Simply use varistors and connected to the protected IC or device circuit, when the transient voltage is higher than a certain value, the varistor resistance rapidly drops, turned a large current, thereby protecting the IC or appliances equipment; when the voltage drops below the operating voltage varistor, varistors high resistance, almost open, and thus will not affect the normal operation of the device or electrical equipment.
Zinc oxide varistor connected in parallel circuit generally used when the voltage across the resistor changes rapidly, resistance short circuit current fuse blows, play a protective role. Metal oxide varistors in the circuit, commonly used in the power supply voltage protection and regulation. Set the multimeter measurement 10k file, table pen connected to both ends of the resistor, the varistor should exhibit marked resistance multimeter, if you exceed this value is large, then the varistor has been damaged. Zinc oxide varistors and protected electrical equipment or components used in parallel. When the lightning over-voltage or transient operating voltage VS circuit occurs, varistors and protected equipment and components withstand VS, due to the fast response of the varistor, it exhibits excellent nanosecond time quickly non-linear electrical properties, then the voltage drop across the TGE Glass Coating varistors rapidly, far less than the VS, on such equipment and components to be protected actual withstand voltage is much lower than the over-voltage VS, so that the equipment and components for Free It was over-voltage shocks.

Zinc oxide varistors to protect the inverter application

 Lightning or lightning impulse voltage induced formation sometimes cause damage to the inverter. When the primary-side power supply system with vacuum circuit breakers, shunt opening and closing can also generate a higher voltage shocks. The drive side of the vacuum breaker opens once, formed by coupling the secondary side of high voltage surge spikes. To prevent over-voltage impulse voltage caused damage, usually at the input side of the inverter plus TGE metal oxide varistor application absorbing devices to ensure that the input voltage is not higher than the allowed maximum voltage during the inverter main circuit. When using the vacuum circuit breakers, the impact should be formed using an additional RC surge absorber. If the transformer primary vacuum circuit breakers, because to ensure the control timing before the first drive is disconnected vacuum circuit breakers.
Most factories are powered generator, or use the generator for a rainy day, when the generator has a fault, the output of the high-voltage inverter and electronic equipment often burned. This condition is often seen in our Shenzhen have had a wire drawing plant once it broke two dozen sets of 30KW inverter, discontinued ten days, causing heavy losses in the generator plant equipment to engage a lot of protection methods the effect is not obvious. Then join metal oxide varistor identification on the input of the inverter or instrument air switch, depending on the voltage 380V with a 821K, 220V with a 471K, so that when a high voltage varistor will be short-circuited, air switch trip, the protection of the inverter, Inverter failure rate is greatly reduced.
Note zinc oxide varistor must be connected to the output end of the air switch, parallel (three-phase triangular connection) wattage varistor size is not critical, a little input current is large is selected relatively large varistor or several varistors in parallel. When the TGE metal oxide varistor theory play a role in it will immediately complete a short circuit. Then switch also requires good air quality equipment, quick response and protect current is not too big.

The main characteristics of zinc oxide varistors and precautions

TGE mov metal oxide varistor is a zinc oxide as the main body, add a variety of metal oxides, various metal oxides classic electronic ceramics made classic electronic ceramics made of polycrystalline semiconductor ceramic element ʱ?? Because of its unique non-linear conductivity of polycrystalline semiconductor ceramic element.
 Because of its unique non-linear electrical conductivity and flow capacity, low voltage limit, fast response, Sobig and flow capacity, limiting low voltage, fast response, polarity, voltage and low temperature coefficient characteristics, widely used power, resistance, low voltage temperature coefficient, widely used in electric power, telecommunications, railways, telecommunications, chemical, petroleum and other areas set up communications facilities, railways, telecommunications, chemical, oil and other fields of facilities and equipment from momentary voltage surge damage. Prepare against momentary voltage surge damage.
 metal oxide varistor testing and protected electrical or components in parallel. When the circuit voltage surge does not appear, varistor surge work when the circuit voltage does not appear, varistors in pre-breakdown, the equivalent circuit for the grain boundary resistance is about the pre-breakdown region, etc. Validity circuit grain boundary resistance of about 10 1012 12 ~ 10 1013 13Ω / cm / cm, the varistor is high impedance, high impedance does not affect the varistor does not affect the normal operation of equipment to be protected; electric sound occurs when the circuit the normal operation of equipment to be protected; when the surge voltage circuit occurs, since the response speed is very varistor surge voltage, since the TGE varistor metal oxide fast response, it quickly turned nanosecond time.

Zinc oxide varistor of use

TGE metal oxide varistor basics is a non-polar overvoltage protection element, whether it is AC or DC circuits, simply TGE metal oxide varistor sizing and is to protect electrical equipment or components parallel protection device purpose

Protection of zinc oxide varistors

(1) distinguish between power supply protection, or signal lines, data lines with TGE Varistor for counter protection, they are to meet different technical standards.
(2) Depending on the varistor applied continuous operating voltage can be across the line with a varistor can be divided into AC or DC with the use of two types, varistors in both voltage stress different aging characteristics performance.
(3) According to the varistor withstand abnormal over-voltage characteristics of different, can be divided into varistor for surge suppression, high-power and high-energy type of these three types.
Surge suppression: is used to suppress lightning over-voltage and over-voltage and other transient over-voltage varistor, this transient overvoltage occurs it is random, and current-voltage non-peak periods may be Big. The vast majority mov metal oxide varistor fall into this category.
High power type: refers to the absorption cycle for continuous bursts appear varistor, for example, and connected to the switching power converter varistor voltage cycle where impact occurs, and the cycle shows that the energy value may be calculated in general out, the peak voltage is not large, but the high frequency of occurrence, the average power is considerably large.
Energy Type: generator means for absorbing the excitation coil, and other large lifting electromagnet coil inductance coil magnetic energy varistor voltage is, for such applications, the main technical indicators are energy absorption capability.
Varistor protection, the vast majority of applications, it can repeatedly effect, but sometimes also to make it into the current fuse as a "one-off" protection device. For example, and then on some of the short-circuit current transformer load contacts TGE metal oxide varistor identification.

High voltage gradient zinc oxide varistor formulation and preparation methods

Reasonable formula of TGE metal oxide varistor sizing is preferably the component with the content of the zinc oxide varistor, prepared using the formulation of zinc oxide varistor with up to 350 ~ 600V / mm high voltage gradient, while at the high voltage gradient, oxidation zinc varistor capable of maintaining good nonlinear properties, electrical properties and anti-aging properties, in order to meet the practical application of electronic components, such as arrester miniaturization requirements. The preparation method of zinc oxide varistor resistance of the zinc oxide film sub-component and trace ingredients and mix evenly matched tiny size, reduce the amount of contamination, while the addition of the low-temperature thermal processes during the sintering process leaving the metal oxide varistor basics to form a stable grain boundary structure, help to improve the stability of the zinc oxide varistor and a secondary heat treatment during the phase transition of bismuth oxide, thereby improving the electrical properties of TGE Glass Coating varistors.
Zinc oxide can be inserted to corrosion or food supplement zinc, but the product demanding, especially to control the content of harmful heavy metals.
Zinc oxide itself is not toxic, but can be inhaled zinc oxide particles are harmful.
Zinc smelting industry, preparation of brass, galvanized work are likely to produce zinc oxide smoke.
To prevent smoke, galvanized iron can not be welded directly, you must first remove the surface film of zinc.

Zinc oxide varistors major role in the electrical industry

Many TGE mov varistor for counter used in the product must use explosion-proof zinc oxide varistors, which is specified in the Design Manual: The controller does not allow the choice of non-explosion type varistor varistors, air-conditioning control panel functions as designed distinction, lightning varistor generally refers to the use of varistors between power line and the earth, sometimes leaving the voltage rise due to poor ground between line and ground, so the ratio between the line and usually use the occasion higher nominal line varistor voltage. Varistor in the circuit must be considered able to withstand the lightning over-voltage, over-voltage and over-voltage transient frequency effects. Lightning varistor and fuse or general discharge with the use of the power portion of the first stage ZNR varistor in parallel with the power transformer primary coil ends, with fuse tubes series circuit, surge voltage suppression.
Under normal circumstances, voltage, resistance zinc oxide varistors great can be achieved by Meg level (the current flowing through it only microampere level, can be ignored), in the open state, no effect on the circuit. But when you experience a power voltage exceeds the breakdown voltage, its resistance suddenly reduce design to a few tenths of Europe even in Europe, up to the current moment by thousands of amperes, ZnO varistor immediately turned on by the deadline, because it and power supplies in parallel, so soon the power fuse blows, the main circuit board to prevent burn out. In addition, when faced with a slight momentary power surge fluctuation (220 ± 10%), varistor buffer will absorb this flow Chung clutter, there are encountered lightning, transformers and other inductive circuit switching operation, instantaneous overpressure effect produced on varistor, its resistance suddenly decreases, the current through the large drainage role to play to protect the entire circuit, this effect is called over-voltage protection. Varistors ZNR common in the schematic representation.
Zinc oxide varistors can also be used as over-voltage protection. Over-voltage atmospheric over-voltage and over-voltage points. Atmospheric over-voltage caused by lightning: Operating overvoltage is due to mutations in the electrical system status, sharp electromagnetic energy caused by the conversion. TGE metal oxide varistor theory is mainly used for lightning induced over-voltage protection, over-voltage electronic devices (surge) absorption, relay contacts spark arrestor, transistors, thyristors, integrated over-voltage protection switch current.

Zinc oxide varistors used in automotive circuits

Automotive products of TGE metal oxide varistor symbol have become increasingly demanding, more and more attention because of the zinc oxide varistor has a good protective effect, good or bad quality can directly affect the use of the car, zinc oxide varistors and at the circuit input is broken, there is no impact on the normal circuit operation, when for some reason caused by the input voltage is increased to a certain value. varistor will burn to protect further damage to the circuit. (Varistor protection element one-off, so after the breakdown want to change with the type of new elements)
1. zinc oxide varistor structure like two characteristics consistent back-coupled regulator, which is basically the same nature. The main characteristics of the varistor, when the ends of the applied voltage is within the nominal rating, its resistance value is almost infinite, in a high impedance condition, the leakage current of <50 microamps, when the voltage across it slightly exceeded rated voltage, its resistance drops sharply immediately in the conduction status, the operating current increases several orders of magnitude, and the reaction time is only in nanoseconds. metal oxide varistor application in foreign commonly known as "chopper" and "limiter", which is from its practical effect and its name.
2. zinc oxide varistor in the circuit can absorb such counter electromotive force, thereby effectively protect the switching circuit from damage. In the car the most used appliances or car computer board in power protection circuit, TGE metal oxide varistor testing Toyota cars computer board with a sheet of black circle, while American cars and Daewoo cars in the pressure-sensitive computer board Most resistance is red, if the car alternator voltage regulator failure, resulting in long lines and battery voltage is too high or the battery pile loose, disengage and start using the power of the power to start the engine, often cause the computer board pressure sensitive resistor damaged.

Zinc oxide varistor selection

Selection of TGE Glass Coating varistors before, you should first understand the following related technical parameters: Nominal voltage is at a predetermined temperature and DC flow, voltage across the varistor. Leakage current is at 25 ℃, when the application of the maximum continuous DC voltage, varistor flowing current value. Level refers mov metal oxide varistor voltage by 8/20 rating current pulses at both ends exhibit voltage peaks. Through traffic is applying a predetermined peak current pulse current (8 / 20μs) waveform when. Surge environmental parameters include a maximum inrush current Ipm (or the maximum surge voltage and surge Vpm source impedance Zo), surge pulse width Tt, the minimum time interval of two adjacent surge Tm and scheduled TGE high voltage varistor working life period, the total number of surge pulses N and the like.

Works zinc oxide varistor

TGE varistor metal oxide is a resistor made of zinc oxide in Taiwan is called the surge absorber, zinc oxide TGE metal oxide varistor application voltage because of the change in resistance has nonlinear way (positive and negative) also symmetry, and Can abnormal voltage response line, absorbed most of the surge / surge energy while suppressing the abnormal voltage to a safe range so that safety and stability to improve lines, and thus subject to many areas of favor.

Zinc oxide use

Another major use of zinc oxide is used as a coating, 1834, for the first time became the watercolor, but insoluble in oil. But soon the problem will be solved by a new zinc oxide production process. In 1845, Leclair began mass production of zinc white oil paint in Paris, 1850, zinc oxide became popular throughout Europe. High purity zinc oxide, so that in the 19th century, some artists painted zinc white as a background in painting, but these paintings have appeared through the crack years later.

Oxide surge arresters a Note

Glass Coating MOV leakage current meter are provided online, in order to monitor the health of the arrester. Live leakage ammeter reflected by external current and porcelain valve arrester currents through the insulation and arrester valve disk.

(1) Lightning Online abnormal increase in leakage current meter reading

Moisture within the metal oxide arresters is mainly caused by bad seal. Moisture sources are:

① the arrester production process, installation humidity exceeded;

② valve and internal parts drying is not complete, some moisture retention;

③ when assembling the seal leak put, put side. Or between the seal and the seal cover folder porcelain debris.

④ run after a period of damage caused by the sealing member into the tide.

(2) Lightning-line leakage current meter reading to reduce or even zero.

Zinc Oxide arresters

Zinc blocks hydroxide is an inorganic compound with the chemical formula Zn (OH) 2, are amphoteric hydroxides. Zinc hydroxide by one divalent zinc and two hydroxide ions. At room temperature as a white solid, insoluble in water. It can be applied to the arrester MOA called oxide surge arresters according to the structure can be divided into two categories;
Porcelain jacket; porcelain Glass Coating MOV by anti-contamination performance is divided into four grades, Ⅰ level for the ordinary type, Ⅱ grade for use in moderate polluted areas (creepage distance of 20mm / KV), Ⅲ grade for use in heavy contamination areas (creepage distance of 25mm / kV), grade Ⅳ is for Severely dirty areas (creepage distance of 31mm / kV).
Composite coat; composite jacket MOA is a composite material made of silicone rubber jacket, and use high-performance zinc oxide varistor, using a special internal structure, assembled with advanced technology methods, with silicone rubber material and the zinc oxide varistor dual advantages. This series of products in addition to having all the advantages of porcelain coat MOA, the other having insulation properties, high resistance to contamination performance, excellent explosion-proof performance and small size, light weight, usually maintenance free, unbreakable, reliable sealing, anti-aging Excellent

Zinc oxide block in Reactive power compensation energy-saving devices in the

In order to limit the instantaneous capacitor cut dangerous overvoltage arrester is commonly connected between the conductor and the ground, in parallel with the protective equipment. When the protected equipment operating at normal operating voltage, lightning does not move, that is regarded as disconnection. If an over-voltage, and is threatening the protective equipment insulation, surge arresters immediate action, the impact of high voltage current to the earth, thereby limiting the voltage amplitude, the protection of electrical equipment insulation. When the overvoltage disappears, the arrester rapid restitution, enabling the system to normal supply, the role of lightning is a discharge gap through a parallel or non-linear resistance to the role of cut pieces of the invasion wave flow, reduce equipment to be protected by the overvoltage value. Surge arresters can be used to protect the atmosphere over-voltage, also be used to operate the overvoltage protection. Effect is to limit overvoltage arrester to protect electrical equipment.
Zinc blocks selection and installation, should be based on their connections, possible over-voltage times capacitor capacity and surge capacity may check; lOkV voltage level and the complement system, the Zinc Oxide discs should normally be connected to the "phase one between the land ", the characteristics of this wiring arresters are higher, such as when a phase to ground fault occurs, the two non-fault phase arrester three-phase capacitor must withstand the impact of savings overvoltage, phase overvoltage We had to be subject to two levels of protection on the ground arrester residual voltage of algebra and the like, which is the inadequacy of the wiring pattern.

History of zinc oxide

ZnO blocks The other main use is as a coating in 1834, first became watercolors, but insoluble in oil. But soon the problem will be solved by a new Zinc Oxide blocks production process. In 1845, Leclair began mass production of zinc white oil paint in Paris, 1850, zinc oxide became popular throughout Europe. High purity zinc oxide, so that in the 19th century, some artists painted zinc white as a background in painting, but these paintings have appeared through the crack years later.

In the second half of the 20th century, Zinc Oxide discs is used in the rubber industry. In the 1970s, the second largest use of zinc oxide is copy paper additives, but in the 21st century as zinc oxide copy paper additives practices have been eliminated.
November 1, 2008 to 15, the researchers gave mice fed a combination of protein such particles, successful shot to particles in the mice glowing image.

Zinc oxide is an oxide of zinc

ZnO blocks is an oxide of zinc. Insoluble in water, soluble in acid and alkali. Zinc oxide is a common chemical additive, widely used in plastics, Portland products, synthetic rubber, lubricants, paints, ointments, adhesives, food, batteries, flame retardants and other products of the production. Zinc Oxide discs energy band gap and exciton binding energy greater transparency , Chang Wen Faguang has excellent performance, liquid crystal display in the field of semiconductors, thin film transistors, light-emitting diodes and other products are used. In addition, the micro-particles of zinc oxide as a nanomaterial also begun to play a role in the related fields.

Zinc Oxide blocks offline manufacturers mainly in Liaoning (Dalian), Shandong (Weifang), Hebei (gaoyi, Xingtai), Jiangsu, Zhejiang and other Zinc oxide, the production of 99.7% of the content-based, commonly known as 997 (99.7) Zinc oxide.