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Working of Metal Oxide Varistor (MOV)
Working of Metal Oxide Varistor (MOV) The resistance of the Metal Oxide Varistor (MOV) is very high. First, let us consider the component to have an open-circuit as shown in figure . The component starts conducting as soon as the voltage across it reaches the threshold voltage. When it exceeds the threshold voltage, the resistance in the MOV makes a huge drop and reaches zero. This is shown in the figure 1(b). As the device has very small impedance at this time due to the heavy voltage across it, all the current will pass through the metal oxide varistor itself. The component has to be connected in parallel to the load. The maximum voltage that will pass through the load will be the sum of the voltage that appears across the wiring and disconnect given for the device. The clamp voltage across the MOV will also be added. After the transient voltage passes through the component, the Metal Oxide Varistor (MOV) will again wait for the next transient voltage. This is shown in the figure 1(c). MOV Performance The varistor is mainly used to perform as a line voltage surge suppressor. The device does not conduct when the voltage across it is below the clamping voltage. But, if a high surge (lighting) that is higher in rate that a varistor can handle is passed through it, the component will not perform. The resulting current will be so high that it will damage the Metal Oxide Varistor (MOV). The performance of the varistor will slow down with time even if small surges pass through it. The life of a MOV will be explained through the manufacturers chart. The chart will have graphs and readings between the current, time and also the number of transient pulses that passes through the varistor. Another main reason that affects the performance of a Metal Oxide Varistor(MOV) is the energy rating. When there is an increase in the energy rating, there will be an exponential change in the life of the varistor. Thus, there will be a change in the transient pulses that the device can manage. This increases the clamping voltage when each transient breaks down. The performance can be increased by connecting more varistors in parallel. An increase in rating will also help in the process. One of the best features of the Metal Oxide Varistor (MOV) is its response time. The spikes are shorted through the device within nanoseconds. But the response time can be affected by the mounting design method and inductance of component leads. [View Details]
What is a ceramic disc capacitor
What is a ceramic disc capacitor? A ceramic disc capacitor is a capacitor constructed with a ceramic disc as the dielectric. You'll recall that the basic definition of a capacitor is two conductors separated by an insulator (dielectric) of some kind. As a charge is driven onto one plate of a capacitor, the extra charge there builds up an electric field. Each charge arriving on one plate forces a charge off the other plate. Charge (and, therefore, voltage) builds. Let's build one to see how it works. Imagine a thick coin of some kind, but made of ceramic. You will (of course) have a ceramic disc. If you coat each face with metal and attach a lead to it, you'll have the basic construct. Note that the edges of the disc are left uncoated, and the two faces, which are conductive now, are insulated by the disc. Just dip the capacitor into a phenolic or epoxy to coat it and it's ready to go, except for the labels. These caps are used in tuning or decoupling applications in RF circuits. And the leads are a dead giveaway to their through-hole use. Crimped or straight leads, please? Use the link below to view some pictures, and all this will make a lot more sense. [View Details]
How to select a VCR ZnO Varistor？
How to select a VCR ZnO Varistor? For most applications, the selection has 6 processes: Normal operating conditions of the varistor. Varistor voltage: the voltage value under 1mA constant current test. Select the ZnO with higher voltage. A.C. / D.C.: max.rms.or DC voltage. Select the max. voltage equal or higher than the peak working voltage. The transient energy absorbed by the ZnO. To determine the energy absorbed in the ZnO, the following equation can apply: E=K×IP×Vc×T Where K is a constant. K value are 1.0 for a rectangular waveform, 1.4 for a 10/1000μs and 8/20μs waveform. And IP is the peak current applied, VC is the clamping voltage which was current applied. T is the pulse width. It must note one thing that the rated energy and the energy absorbed in a Varistor may not be identical. It has a situation that a ZnO varistor with better clamping voltage will absorb less energy. It is very important to emphasize that poorer ZnO varistor will absorb higher energy in the ZnO varistor itself and the better ZnO varistor which performs a lower clamping voltage will absorb less energy, yet actually provides a better over-voltage protection. Max. transient voltage that the equipment to be protected can withstand. Select lower clamping voltage than the equipment can endure. It is easy to find ZnO varistor clamping voltage from V-I curve when the transient current is known. Max. peak transient current that the varistor can withstand. The peak transient current can be measured in the circuit. If the transient is generated by an inductor, the peak current will not be more than the inductor change current. When the transient voltage and the circuit line impedance is known, the transient current can get by using a graphical analysis. Number of transient currents expected surge during life evaluates the total transient numbers in the circuit and the max. Peak current then selects the suitable model ZnO varistor that can endure. Determine power dissipation requirements. If the transients generate heat in a ZnO Varistor too quickly, it can not be transferred during the pulse interval and will cause the ZnO varistor fail. Under this condition, the power dissipation so developed must be within the specifications shown on the ratings tables. It is to be noted that ZnO varistor can only dissipate a repetitive applications that involve substantial amounts average energy dissipation. Furthermore, the operating values will be decreased at high temperature as shown in the following figure. [View Details]
How to select NTC Thermistor
How to select NTC Thermistor The NTC meaning is a negative temperature coefficient, refers to the negative temperature coefficient of semiconductor materials or components, the so-called NTC Thermistor is a negative temperature coefficient thermistor device. It is based on metal oxides, such as manganese, cobalt, nickel and copper as a main material, and the ceramic manufacturing process made. These metal oxide materials have semiconductor properties, because the conductive way completely similar germanium, silicon and other semiconductor materials. The temperature is low, the number of these oxide material carriers (electron and hole) less, so its resistance value is high; as the temperature increases, the number of carriers increases, so the resistance value is lowered. The range of variation of the NTC thermistor at room temperature 10O ~ 1000000 ohms, the temperature coefficient of -2% to -6.5%. NTC thermistor are widely used for temperature measurement, temperature control, temperature compensation. NTC is the resistance exponential relationship is reduced as the temperature rises, the phenomenon and material having a negative temperature coefficient thermistor. The material is sufficiently mixed with manganese, copper, silicon, cobalt, iron, nickel, zinc, and the like of two or more metal oxides, molding and sintering process is made of a semiconductor ceramic having a negative temperature coefficient, can be made (NTC) thermistor. Ratio, sintering atmosphere, sintering temperature, and the structural state of the resistivity and material constants with the material composition varies. Now also appears to the silicon carbide, selenium, tin, tantalum nitride, etc. as the representative of the non-oxide-based NTC thermistor material. Most NTC thermistor semiconductive porcelain spinel structure or other structure of oxide ceramics, having a negative temperature coefficient, the resistance value can be approximately expressed as: where RT, RT0 is the temperature T, T0 when the resistance value, Bn The material constants. Ceramic grain changes due to temperature changes in the resistivity, which is determined by the semiconductor properties. [View Details]
How to Test a Metal Oxide Varistor
How to Test a Metal Oxide Varistor A Metal Oxide Varistor (MOV) is an electronic device that protects an appliance's power supply from voltage spikes and surges in the AC power line. Normally, the MOV has very high electrical resistance. If lightning strikes a nearby power line,the high voltage causes the MOV to become a shunt, preventing the electrical surge from harming sensitive equipment.After this happens, the device's fuse will blow. You can test an MOV(Metal Oxide Varistor) simply by testing its resistance. [View Details]
How a Surge Protector Works (Metal Oxide Varistor)？
How a Surge Protector Works (Metal Oxide Varistor) How a Surge Protector Works? [View Details]
Ceramic chip capacitor production process
Ceramic chip capacitor production process A capacitor is an electrical device that stores energy in the electric field between a pair of closely spaced plates Capacitors are used as energy-storage devices, and can also be used to differentiate between highfrequency and low-frequency signals. This makes them useful in electronic filters Capacitance Value.Measure of how much charge a capacitor can store at a certain voltage Multilayer Ceramic Chip Capacitor Layers of ceramic and metal are alternated to make a multilayer chip Capacitors are devices that store energy in the form of an electric field. They can also be used to filter signals of different frequencies. The capacitance value is an indicator of how much electrical charge the capacitor can hold. Multilayer ceramic capacitors consist of alternating layers of ceramic and metal. The process of making ceramic capacitors involves many steps. •Mixing: Ceramic powder is mixed with binder and solvents to create the slurry, this makes it easy to process the material. •Tape Casting: The slurry is poured onto conveyor belt inside a drying oven, resulting in the dry ceramic tape. This is then cut into square pieces called sheets. The thickness of the sheet determines the voltage rating of the capacitor. •Screen Printing and Stacking: The electrode ink is made from a metal powder that is mixed with solvents and ceramic material to make the electrode ink. The electrodes are now printed onto the ceramic sheets using a screen printing process. This is similar to a tshirt printing process. After that the sheets are stacked to create a multilayer structure. •Lamination: Pressure is applied to the stack to fuse all the separate layers, this created a monolithic structure. This is called a bar. •Cutting: The bar is cut into all the separate capacitors. The parts are now in what is called a 'green' state. The smaller the size, the more parts there are in a bar. •Firing: The parts are fired in kilns with slow moving conveyor belts. The temperature profile is very important to the characteristics of the capacitors. •Termination: The termination provides the first layer of electrical and mechanical connection to the capacitor. Metal powder is mixed with solvents and glass frit to create the termination ink. Each terminal of the capacitor is then dipped in the ink and the parts are fired in kilns. •Plating: Using an electroplating process, the termination is plated with a layer of nickel and then a layer of tin. The nickel is a barrier layer between the termination and the tin plating. The tin is used to prevent the nickel from oxidizing. •Testing: The parts are tested and sorted to their correct capacitance tolerances. •This point the capacitor manufacturing is complete. The parts could be packaged on tape and reel after this process or shipped as bulk. [View Details]
The working principle and characteristics of the Metal Oxide Varistor
The working principle and characteristics of the Metal Oxide Varistor The Metal Oxide Varistor is a zinc oxide as the main component of the metal oxide semiconductor nonlinear pressure limiting resistor. The volt-ampere characteristics of the Metal Oxide Varistor is a continuous and increasing, so it does not exist continued flow blocking problem. Its working principle is the zinc oxide and additives of Metal Oxide Varistors "sintering" under certain conditions, the resistor will be affected by the strong influence of the voltage, the sharp rise in the current as the voltage rises, the rising curve of a nonlinear index. When the normal working voltage, a Metal Oxide Varistor is a high resistance state. When the arrival of the surge, it is in the path state, a strong current flow through itself leaked into the earth. Surge After this he immediately restored to the high resistance state. Metal Oxide Varistor several important parameters: A: varistor voltage: varistor voltage is generally considered to be at a temperature of 20 degrees on the Metal Oxide Varistor 1mA current flowing corresponding to the voltage across the resistor. Varistor voltage in the AC power grid, in general, to be higher than the peak voltage of the grid is 0.7 times the peak voltage and the peak voltage is generally considered to √ 2 times the AC grid voltage (DC peak voltage is 1.2 times the rated voltage). Expressed by the formula: VN = VNH × √ 2 ÷ 0.7 Where VN varistor voltage; VNH rated voltage for the grid. B: leakage current: leakage current refers to the current under normal circumstances by the order of magnitude of the Metal Oxide Varistor microamps. Leakage current is smaller the better. Special emphasis should be placed on the leakage current must be stable, not allowed to work automatically increased if it is found that the leakage current is automatically elevated, it should be immediately eliminated, because of the instability of the leakage current is accelerated aging SPD and SPD explosion the direct cause. Select leakage current parameters, you can not blindly pursue the smaller the better, as long as it is in the grid within the allowed value range, select the leakage current is relatively slightly larger than some of the lightning, but more stable. C: response time: response time is equal to the time required by the varistor voltage, the voltage at both ends of the SPD and SPD this time completely turned. The Metal Oxide Varistor about the response time of 25ns. D: parasitic capacitance: a Metal Oxide Varistor generally have a large parasitic capacitance is a parasitic capacitance generally between a few hundred picofarads to several thousands of picofarads, and thus it is not conducive to the protection of high-frequency electronic system. Because this parasitic capacitance of the high-frequency signal transmission will be distorted, thus affecting the normal operation of the system. Thus the protection of high-frequency system, should choose low parasitic capacitance of Metal Oxide Varistor type lightning. Its advantages: 1, residual depression. 2, fast response time, 25ns or so. 3, free wheeling. 4, Notices telesignalling function can achieve deterioration instructions and failure, therefore, its protective effect safe and reliable. It is commonly used in the current power supply system products, especially electricity, telecommunications, power supply field, is thriving. Its drawbacks: leakage current; parasitic capacitance larger, is not conducive to the protection of high-frequency electronic circuits. [View Details]
Metal Oxide Varistors-Taping Specification
Metal Oxide Varistors-Taping Specification Established in 1978, SHIN-HANG Electronics Enterprise Co., Ltd. is an ISO 9001-certified manufacturer committed in the manufacturing and selling of Ceramic Capacitors (Temperature compensating, High voltage, Semi-conducting, Low-DF, AC&Y safety standard type, Multilayer Ceramic Capacitors), Metal Oxide Varistors, NTC Thermistor, Electrolytic Capacitor, Safety Capacitors, Film Capacitor and Resettable fuse. In 2007, our branch factory in Guang Dong China - Zhan Qun Electronics Co., Ltd. has set up to supply the international market of electronic components. Besides manufacturing and selling, we also offer subcontracted services. Our company is not only limited to local areas, we are also opened to all business opportunities worldwide. We utilize automatic layout and standard working system to improve the rate of production and increase work efficiency. We strictly apply the main management philosophy of the ISO 9001 system to our production process. Thus, all products are ensured to be of the highest quality. We are looking forward to a profitable partnership with you. Metal Oxide Varistors-Taping Specification Transient Voltage Surge Suppressors [View Details]
Metal Oxide Varistors-VCR’s MN Series
Metal Oxide Varistors-VCR’s MN Series Established in 1978, SHIN-HANG Electronics Enterprise Co., Ltd. is an ISO 9001-certified manufacturer committed in the manufacturing and selling of Ceramic Capacitors (Temperature compensating, High voltage, Semi-conducting, Low-DF, AC&Y safety standard type, Multilayer Ceramic Capacitors), Metal Oxide Varistors, NTC Thermistor, Electrolytic Capacitor, Safety Capacitors, Film Capacitor and Resettable fuse. In 2007, our branch factory in Guang Dong China - Zhan Qun Electronics Co., Ltd. has set up to supply the international market of electronic components. Besides manufacturing and selling, we also offer subcontracted services. Our company is not only limited to local areas, we are also opened to all business opportunities worldwide. We utilize automatic layout and standard working system to improve the rate of production and increase work efficiency. We strictly apply the main management philosophy of the ISO 9001 system to our production process. Thus, all products are ensured to be of the highest quality. We are looking forward to a profitable partnership with you. [View Details]

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