Siov metal oxide varistors data book 2008 schmidmultitech sro. The surfaces of the intercrystalline fracture follow. Learn more a varistor is an electronic component that protects expensive devices from harmful power surges, much like a shock absorber. How to test a mov metal oxide varistor surge protector. The operation of metal oxide varistor and silicon carbide varistor are very similar. This means that this volume is once again a handbook on the fundamentals of metaloxide surge arresters in highvoltage systems, reflecting the stateofart in terms of technology and standards. For example if there is a power surge, the varistor, normally having a very high resistance, responds to the voltage spike by absorbing its energy with a very low. Application guidelines overvoltage protection metal. Excessive voltage triggers the mov into action, so to size it for surge. Metal oxide varistors, also known as movs are one of the most common types of varistors. The metal oxide varistor or mov for short, is a voltage dependant resistor in which the resistance material is a metallic oxide, primarily zinc oxide zno pressed into a ceramic like material. A varistor remains nonconductive as a shunt mode device during normal operation when voltage remains well below its clamping voltage. The most common modern type of varistor is the metaloxide varistor mov. Varistor or voltage dependent resistor vdr resistor guide.
Because standard metal oxide varistors, gas arresters, and avalanche diodes do not provide the user with a visual indication of the integrity of the protection capacity, an external means of testing is required. If lightning strikes a nearby power line, the high voltage causes the mov to become a shunt, preventing the electrical surge from harming. They are voltage dependent, nonlinear devices that provide transient suppression. If lightning strikes a nearby power line, the high voltage causes the mov to become a shunt, preventing the. Here the body is made of a metal oxide, mostly zinc oxide grains. To achieve the lowest possible protection level as described in chapter selection procedure, section 1. Normally, the mov has very high electrical resistance. Application guidelines overvoltage protection metaloxide. Metal oxide varistor mov are voltage dependent symmetrical resistors intended to protect equipment from transient voltages resulting from lightning strikes. It is impossible to predict when these failures will occur without some form of testing. A operating conditions and circuit design 1 varistor shall not be operated beyond the, breakdown, flaming or glowing. Since sic varistors had some serious drawbacks, another type of varistors the metal oxide varistors were developed. Ensure suitability of siovs through reliability testing during the designin phase.
First, it is normal for the peak varistor voltage measured with ac current to be. The power so developed must be within the specifications shown on the. Varistor testing introduction as with any device, metaloxide varistors possess a number ofway to assure correlation of measured values between maker and user. Testing varistors against the vde 0160 standard semantic scholar.
We also have an extensive resource database for sourcing and crossreferencing parts. May 08, 2017 metal oxide varistors, also known as movs are one of the most common types of varistors. The main difference between a silicon carbide varistor and a metal oxide varistor is the amount of leakage current. Dear all, i am using an mov for surge protection in one of our application. How to test a mov metal oxide varistor surge protector device last updated on july 7, 2019 by swagatam 9 comments the article discusses a set up for testing movs which are special devices specified for absorbing instantaneous high surge currents that may accidentally occur in our mains electrical lines. An attractive property of the metal oxide varistor, fabricated from zinc oxide zno, is that the electrical characteristics are related to the bulk of the device. The 14d of 14mm radial leaded varistor devices protects against overvoltage transients such as lightning, power contact and power induction. 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 oxides, sandwiched between two metal plates, which constitute the electrodes of the device. One of the movs connected between earthgnd and line fails frequently. Accroding to the market requirement for a high quality varistor, and based on the problems exit during production procedure, fatech team developed a kind of high performance, reliable varistor special for surge protection devicesspd, and established new production workshop specially for metal oxide varistors production. A metal oxide varistor mov is an electronic device that protects an appliances power supply from voltage spikes and surges in the ac power line. Aug 28, 2007 metal oxide varistor mov are voltage dependent symmetrical resistors intended to protect equipment from transient voltages resulting from lightning strikes. Metal oxide varistor mov, basics, working, specifications.
I have a tnr7v471k which i have taken out of circuit. They are a type of nonlinear device that feature similar characteristics to zener diodes. A metal oxide varistor is a device used as a component in electrical equipment. A wide variety of varistor testing options are available to you, such as usage, power. Specifications are subject to change without notice. Varistor symbol and applications metal oxide varistor. Bulk on tape and reel on tape in ammopack fanfold the basic ordering code for each option is given in tables titled varistors on tape on reel, varistors on tape in ammopack and varistors in bulk. Figure 4 shows the simplified equivalent circuit of a metal oxide varistor. This is achieved through a special dielectric material formulation which also results in higher repetitive surge ratings than other mov types. Pdf reliability evaluation of metal oxide varistors for. It provides very good voltage transient protection and is now quite popular. Typical values are characteristics of the device and are, part of the testing requirements. A resistor is a circuit that does not conduct electricity well.
The boundary between each grain and a neighbor forms a diode. Energy ratings are based on a shift of varistor voltage of less than 10% of the initial value. G series metal oxide varistor general purpose ul 1414 and 1449 approved csa 097864 approved 85c maximum temperature actual size the g series is the standard metal oxide varistor, additional technical information and specifications. The devices have a high current handling, high energy absorption capability and fast. A simple equivalent circuit representing a metal oxide varistor as. Large varistors exhibit nonuniform current flow, but the nonuniformity is on a macroscopic scale rather than on a microscopic scale, and it largely results from imperfect ceramic processing. They are used to protect vulnerable electronic circuits and components from overvoltage conditions that can cause damage. The first generator was used for basic mov testing in order to produce the. The primary objective of this thesis is to design, construct, and test two surge generators. G metal oxide varistor summary of, 625vac or 12 to 825vdc.
Varistor testing introduction this note details the common tests of varistor parameters and describes suitable test methods using simpli. The name has been coined by linguistic blend of words. Sep 22, 2015 the operation of metal oxide varistor and silicon carbide varistor are very similar. The heating is greatest near the circumference of the. Metal oxide varistormov failure all about circuits. Oct 07, 2019 varistor testing introduction as with any device, metal oxide varistors possess a number ofway to assure correlation of measured values between maker and user. A number of developments in technology and application of mo surge arresters as well as in standardization have taken place in the past years. Simple and inexpensive, the mov absorbs the energy in a surge, preventing it from damaging other devices in a circuit. This catastrophic failure occurs when absolute maximum ratings in.
A varistor is an electronic component that protects expensive devices from harmful power surges, much like a shock absorber. Thus, for equipment to pass burst testing successfully, design line filter, grounding concept, case is as critical as the choice of varistor. Vdr metal oxide varistors standard additional resources ordering information the varistors are available in a number of packaging options. All tests are performed at 25oc, unless otherwise speci. The first edition of our guidelines for the dimensioning, testing and application of metal oxide surge arresters mo surge arresters for use in mediumvoltage systems appeared in 1994. Hi, is there a simple test one can do to check if a metal oxide varistor is defective or not. Figure 4 shows an ir image of the surface temperature of a 4. The test circuits and methods given herein are intended as a general guide.
Littelfuse varistors basic properties, terminology and theory. Nte1v010 thru nte1v300 nte2v010 thru ntev480 nte524v thru. The downside is that if they stop a power surge, they can effectively burn out, but the user may have no idea this has happened. Accepting the premise of prevalent 1000 highenergy surges and subjecting typical metaloxide varistors to the stress from a test performed with a prototype. Energy the maximum electrical energy which can be dissipated within the varistor by a single impulse of 10 x s current waveform with continuous voltage applied. Within the useful varistor voltage range, the voltagecurrent relationship is approximated by the expression. What is a metaloxide varistor and how it protects a. Metal oxide varistor basics mov is the most commonly used type of varistor.
Metal oxide varistors tnr when the surge energy much higher than the rated maximum energy is applied to the varistors, it may blow up and catch fire. If iec 645 has been taken into account when selecting varistors, they will normally also handle the burst pulse energy without any problems. The ciii varistor series of metal oxide varistors movs are specifically designed for applications requiring high surge energy absorption ratings and superior multiple pulse absorption rating. They are also known by the name vdr voltage dependent resistor and have nonohmic characteristics. Integrated varistors consist of a 40ka varistor building block mov with an integral thermally activated element. Varistor testing introduction as with any device, metal oxide varistors possess a number of, currents, the user must exercise appropriate safety precautions. What is a metaloxide varistor and how it protects a drive. To assure our customers quality general electric metal oxide varistors and other products and services at international standards, galco maintains iso90012000 certification. A operating conditions and circuit design 1 varistor shall not be operated beyond the, breakdown, flaming or. Specialty movs metal oxide varistors are available in unique form fits and possess various voltage range and surge capabilities. Make us your source for general electric metal oxide varistors and other products.
Users should verify actual device performance in their specific applications. If a transient pulse often measured in joules is too high, the device may melt, burn, vaporize, or otherwise be damaged or destroyed. During the sintering process the metal oxide powder transforms to a dense ceramic body with varistor properties. A surge in excess of the specified withstanding surge current may cause short circuits or package rupture with expulsion of material. The metal oxide varistor or mov is a voltage dependent, nonlinear device that provides excellent transient voltage suppression. Pdf comparative study of metal oxide varistors movs for. If iec 645 has been taken into account when selecting varistors, they will normally also. The first edition of our guidelines for the dimensioning, testing and application of metaloxide surge arresters mo surge arresters for use in mediumvoltage systems appeared in 1994.
Therefore, they come under non linear type of resistors. Epcos metal oxide varistors are designed for specific applications and should not be used for purposes not identified in our specifications, application notes and data books unless otherwise agreed with epcos during the designinphase. Jameco sells metal oxide varistor and more with a lifetime guarantee and same day shipping. Metal oxide varistors consist of approximately 90% zinc oxide as a ceramic base material plus other filler materials for the formation of junctions. A varistor is a varying resistor whose resistance depends on the applied voltage. Apr 18, 2020 the metal oxide varistor is not a perfect solution to power surges. The voltage across terminals when a test current lt. Metal oxide varistors mov, electrical characteristics and test methods. Metaloxide surge arresters in highvoltage power systems. Mov14dxxxk series metal oxide varistor rohs directive 200295ec jan.
They are cheap to manufacture, which means they are often used in inexpensive surge protectors. Pdf comparative study of metal oxide varistors movs. A similar development is taking place in the american surge arrester testing standard ieee c62. So, in test circuits, you start by determining the varistor voltage for every single type as. Jul 07, 2019 how to test a mov metal oxide varistor surge protector device last updated on july 7, 2019 by swagatam 9 comments the article discusses a set up for testing movs which are special devices specified for absorbing instantaneous high surge currents that may accidentally occur in our mains electrical lines. Integrated varistors consist of a 40ka varistor building block mov with an. Metal oxide varistor described above, the mov is a nonlinear transient suppressor composed of zinc oxide zno silicon carbide varistor at one time this was the most common type before the mov came into the market. Metal oxide varistors, more commonly known as movs are devices that provide excellent transient voltage suppression. The metal oxide varistors offer a choice of varistor voltages from 18v to 1800v and vrms voltages from 11v to 1100v. A metal oxide varistor, or mov, is an electronic component that protects equipment from voltage surges in a power line, such as from lightning strikes. Metal oxide varistors definition of varistor terms rated rms voltage, rated dc voltage the maximum designated values of power system voltage that may be applied continuously between the terminals of a device varistor voltage test characteristic that is used to classify varistors by type.