Commonly used is zinc oxide zno pressure sensitive resistance, which is mainly based on zinc oxide as raw material, add a variety of trace metal oxides, mixed molding, an overvoltage protection device sintering assembly, the outside encapsulating epoxy resin which can add. Learn more a varistor is an electronic component that protects expensive devices from harmful power surges, much like a shock absorber. Pdf comparative study of metal oxide varistors movs for. The amount of degradation was dependent on the polarity of the measurement relative to the polarity of the pulsing, as well as the energy rating of the device.
Metal oxide varistors, or movs are typically made from a small diskshaped metal zinc oxide material. Metal oxide varistor tvr series, for surge protection, professional manufacturer, high quality, from china original factory. Thinking tvr varistor the first brand of mov shipments. Many industry manufacturers, including current technology, integrate various sizes of radial or straptype movs into their products. They are available in many values for specific voltage ranges. Preparing of powder by weighing, milling, mixing different metal oxide materials. They are used to protect vulnerable electronic circuits and components from overvoltage conditions that can cause damage. A test current of 1 ma dc is typically used to determine. Varistor and the metal oxide varistor tutorial electronicstutorials. Metal oxide varistors high energy disc varistor series metal oxide disc varistors features the disc varistor series of transient surge suppressors are industrial provided in disc form for unique packing by highenergy disc varistors movs intended for special applications customer requiring unique electrical contact or packaging methods.
The most common modern type of varistor is the metal oxide varistor mov. How to make a testing an mov metal oxide varistor surge. This type is commonly known as the metaloxide varistor mov. For this reason, varistors are also called metal oxide varistors mov.
The main difference between a silicon carbide varistor and a metal oxide varistor is the amount of leakage current. A varistor is an electronic component that protects expensive devices from harmful power surges, much like a shock absorber. Nippon chemicon corporation metal oxide varistorstnr manufacturing and selling capacitors and electronics components. Penlington university of northumbria, newcastle upon tyne, uk metal oxide varistors are znobased ceramic devices having highly nonlinear currentvoltage characteristics similar to those of the back to back zener diodes. How to test a mov metal oxide varistor surge protector. The metal oxide varistor is not a perfect solution to power surges. Measuring the energy handling capability of the metal oxide varistors m. The abcs of movs application notes from littelfuse company.
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 resistance. Metal oxide varistor mov are voltage dependent symmetrical resistors intended to protect equipment from transient voltages resulting from lightning strikes. Jul 07, 2019 to demonstrate how to test an mov you would need a 600 v ac source derived by stepping up the domestic 220 v through an auto transformer, and make the circuit set up as shown in the diagram. The test circuits and methods given herein are intended as a general guide. Metal oxide varistor is a voltage dependent resistor with symmetrical voltagecurrent characteristics that is designed to protect all kinds of electronic devices or elements from switching and induced lightening surges. A wide variety of green metal oxide varistor options are available to you, there are 141 suppliers who sells green metal oxide varistor on, mainly located in asia. The last feature is based, in particular, on the electrothermal analysis developed in 3 which is in perfect agreement with the experimental data on failures contained in 10.
Panasonics mov are available in various disc dimensions 5mm to 20mm diameter, varistor voltages and ul certificated. How to make a testing an mov metal oxide varistor surge protector device last updated on february 17, 2018 by admin leave a comment the post talks about a set up for assessment and utilizing movs which can be special devices stipulated for consuming immediate high surge currents that could mistakenly happen in our mains electrical lines. Metal oxide varistor electronics repair and technology news. The figure shows a bridge network which rectifies the 600 v ac to 700 v dc and this dc is then fired across the mov circuit carrying a vulnerable 220 v, 10. The use of mov not only reduces the chance of electrical damage buut also improves equipment reliability. This component is located near the ac supply input and before the bridge rectifier. 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. Hi, is there a simple test one can do to check if a metal oxide varistor is defective or not. A wide variety of varistor testing options are available to you, such as usage, power.
All tests are performed at 25oc, unless otherwise speci. Our metal oxide varitor 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. They are a type of nonlinear device that feature similar characteristics to zener diodes. Amperes volts amperes joules pf 11 14 16 20 100 36 1 0. Varistor with silicon carbide varistor and zinc oxide varistor. Varistor testing introduction this note details the common tests of varistor parameters and describes suitable test methods using simpli. The metal oxide varistor, with its extremely attractive priceperformance ratio. An movs voltage rating, called the varistor voltage is the voltage across a varistor when a current of 1ma is passed through the device. Siov metal oxide varistors data book 2008 schmidmultitech sro. They are cheap to manufacture, which means they are often used in inexpensive surge protectors.
There will also be a presentation of the different mov products littlefuse brings to the marketplace. Jameco sells metal oxide varistor and more with a lifetime guarantee and same day shipping. The power so developed must be within the specifications shown on the. 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. Metaloxide varistors movs subjected to a single highenergy transient displayed an increase in standby current and a decrease in clamping voltage. Zinc oxide varistor tvr seriesproductsvetng thinking ltd. Metal oxide varistor is the most common type of varistor. Apr 18, 2020 the metal oxide varistor is not a perfect solution to power surges. The devices have a high current handling, high energy absorption capability and fast response times to protect against transient faults up to rated limits. I have a tnr7v471k which i have taken out of circuit. Specifications are subject to change without notice. An attractive property of the metal oxide varistor, fabricated from zinc oxide zno, is that the electrical characteristics are related.
It is called so as the component is made from a mixture of zinc oxide and other metal oxides like cobalt, manganese and so on and is kept intact between two electrodes which are basically metal plates. Surge currents of relatively long duration are required for testing maximum energy absorption ca. The metal oxide varistor, mov, is the most widely used form of varistor. D05, d07, d09, d10, d14, d18, d20 metal oxide varistor. Metal oxide film resistors must not be confused with metal oxide varistors, made of zinc oxide or silicon carbide. Low inductance construction with excellent response 6. Measuring the energy handling capability of metal oxide. Please confirm technical specifications before you order andor use.
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. Stacking many varistors in a series as one varistor can increase the clamp voltage of a mov. Metal oxide varistors mov, electrical characteristics and test methods. 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. We are one of the leading manufacturer of varistor. 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. Large capability to withstand high surge current 5. Nippon chemicon offers varistors, which are also suitable for automotive compliance according to aecq200.
Surge currents of relatively long duration are required for testing maximum. Metal oxide varistor mov, basics, working, specifications. Sep 22, 2015 the operation of metal oxide varistor and silicon carbide varistor are very similar. The basic varistor consists of a layer of oxide on a metal sheet, typically zinc. 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.
Electrical testing and classification cylindrical surface and of metal electrodes on the flat surfaces. Electronics tutorial about the varistor and metal oxide varistor or mov which is used in power electronics circuits for protection against transients. The metal oxide varistors offer a choice of varistor voltages from 18 v to 1800 v and v rms voltages from 11 v to 1100 v. Varistor is pressing device of a the most used limit. Properties metal oxide film resistors exceed the performance of metal film and carbon film for the following properties. Reliability evaluation of metal oxide varistors for. Panasonics mov are also know as znr, which stands for zincoxide nonlinear resistor. A metal oxide varistor starts conducting current at rated voltage and it stops the conduction if the applied voltage is below the threshold value. Metal oxide varistors, more commonly known as movs are devices that provide excellent transient voltage suppression. This tutorial will provide an introduction to metal oxide varistors and mov product offerings from littelfuse. The series of a varistor varies depending on the voltage it can hold, the devices it is used to control, and the type of power used in its build.
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. Metal oxide varistors consist of approximately 90% zinc oxide as a ceramic base material plus other filler materials for the formation of junctions. Allowable voltage varistor voltage withstanding surge current 8 20. Metal oxide varistor on sales quality metal oxide varistor.
To demonstrate how to test an mov you would need a 600 v ac source derived by stepping up the domestic 220 v through an auto transformer, and make the circuit set up as shown in the diagram. Basic operation, electrical characteristics, and applications will be discussed. Varistors vary quite heavily between different models. The model obtained permits to calculate the mean time to failure mttf of.
Normally, the mov has very high electrical resistance. Mov14dxxxk series metal oxide varistor rohs directive 200295ec jan. 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. Littelfuse varistors basic properties, terminology and theory. A varistor is an electronic component with an electrical resistance that varies with the applied. Sintering of the discs for several hours at a temperature of 11001200. Users should verify actual device performance in their specific applications. Vdr metal oxide varistors standard additional resources ordering information the varistors are available in a number of packaging options.
Simple and inexpensive, the mov absorbs the energy in a surge, preventing it from damaging other devices in a circuit. Within the useful varistor voltage range, the voltagecurrent relationship is approximated by the expression. Metal oxide varistor mov technology is the most prevalent technology utilized in electrical transient protection products today. 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. The most common modern type of varistor is the metaloxide varistor mov. Vb type t plastic encapsulated type varistor for surge protection features 1. Applying an insulating and passivating layer on the 6. The operation of metal oxide varistor and silicon carbide varistor are very similar. If lightning strikes a nearby power line, the high voltage causes the mov to become a shunt, preventing the. It is generally manufactured from a material such as zinc oxide, zno, although another material that is used is silicon carbide, sic and this provides similar properties.
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