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.