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Fuses and Relay Circuits
Published in Dorin O. Neacşu, Automotive Power Systems, 2020
The most common type of varistor is the metal-oxide varistor (MOV), which contains a ceramic mass of zinc oxide grains, in a matrix of other metal oxides (bismuth, cobalt, manganese) sandwiched between two metal plates (electrodes). The boundary between each grain and its neighbor forms a diode junction, which allows a current to flow in only one direction. When high voltage is applied, the diodes’ junctions break, allowing for a large current. The device survives for a certain time under this large current until the problem is cleared or the circuit is disconnected.
Passive Components
Published in Richard C. Dorf, Circuits, Signals, and Speech and Image Processing, 2018
Michael Pecht, Pradeep Lall, Glen Ballou, C. Sankaran, Nick Angelopoulos
Varistors. Varistors are voltage-dependent resistors that show a high degree of nonlinearity between their resistance value and applied voltage. They are composed of a nonhomogeneous material that provides a rectifying action. Varistors are used for protection of electronic circuits, semiconductor components, collectors of motors, and relay contacts against overvoltage.
Barriers against conducted disturbances
Published in Mark van Helvoort, Mathieu Melenhorst, EMC for Installers, 2018
Mark van Helvoort, Mathieu Melenhorst
A varistor (i.e., varying resistor) acts as a voltage-dependent resistor which has a high resistance at low voltages. The resistance increases when the voltage is increased. The most common-type varistors are MOVs, which are typically based on sintered granular zinc oxide. The contact points between the grains act as diode junctions. Due to the random orientation of the grains, they are suitable for both AC and DC applications. A varistors will not short the circuit, but clamp the voltage at a certain threshold. In a power line this may cause the varistor to heat up which further lowers its resistance and finally may lead to a failure. This process is called thermal runaway. Such failure may be prevented by adding a thermal fuse in series. Over time MOVs degrade beyond acceptable limits and have to be replaced.
Exploring the global publications on varistors using the Scopus database through a bibliometric analysis
Published in Journal of Asian Ceramic Societies, 2022
Muhamad Syaizwadi Shaifudin, Wan Mohamad Ikhmal Wan Mohamad Kamaruzzaman, Malia Athirah Badruddin, Abdul Muiz Aniq Aiman Mohd Suhaimi, Nursabrina Amirah Mohd Nasir, Nur Aiman Syafiq Mohd Hamidi, Wan Rafizah Wan Abdullah, Oon Jew Lee, Mohd Sabri Mohd Ghazali
The fabrication of varistor ceramics commonly involves two methods, first by identifying a suitable preparation technique to obtain ceramic powders with better physical properties for specific applications and second by mixing varistor-based ceramic powders with several possible additives or dopants to enhance both their microstructure and electrical properties. It is important to emphasize that the characteristics of varistor devices are directly depending on to their microstructure. This microstructure, on the other hand, is regulated by the distribution of grain size, grain boundaries, secondary phases, and pores [26]. The keywords associated with “Microstructure” were repeated 162 times, which indicates that most of the researchers discussed the mechanism of varistor characteristics based on their microstructure properties. A breakdown voltage phenomenon occurs due to modification in grain size within the microstructure of varistors, which differentiate the difference between the application of low and high voltage varistors. Varistors have been broadly applied in the electrical system as surge protection devices over a wide voltage range, starting with a few volts for low voltage varistors in miniature devices to tens of kilovolts for high voltage varistors in transmission lines and distribution networks [27].
Effect of microwave sintering on the microstructure and electrical properties of low-voltage ZnO varistors
Published in Materials and Manufacturing Processes, 2018
Kazem Tahmasebi, Mohammad Maleki Shahraki, Touraj Ebadzadeh
Metal oxide varistors with nonlinear behavior are mainly used as transient voltage surge suppressors to limit voltage surges coming from noises, switching, and lightening. Varistors are applied in high, moderate, and low voltages as surge arrester, surge protection device, and surge absorber, respectively. Due to the high nonlinearity and energy absorption capability, ZnO varistors are commercialized in all the mentioned voltage requirements for widespread applications.[1] With the development of microelectronic technology and large-scale-integrated electronics, there is an ever-increasing demand for varistors for low-voltage (less than 100 V) applications, such as automobile and semiconductor electronics.[2]