Today's small manufacturers of varistor manufacturers talk about five kinds of overheating protection technology:
(1) hot melt fuse technology. The technology is to protect the low-melting metal with wax through a certain process installed in the varistor, the varistor leakage current is too large, the temperature rose to a certain extent, low melting point metal fuse, so the varistor from the Circuit excision, can effectively prevent the varistor fire burning. But the thermal fuse there is reliability problems, but also in the environment to strengthen the thermal cycle of only about 5 years of reliable life. In thermal cycling environments, hot melt fuses need to be replaced regularly to maintain normal operation.
(2) the use of spring to pull low melting point solder technology. This technology is currently the vast majority of lightning protection device manufacturers limited pressure SPD technology used in the varistor lead to add a low melting point solder solder joints, and then use a spring to pull the welding point, in the Varistor leakage current is too large, the temperature rises to a certain extent, the welding point of the solder fuse, the spring under the action of the welding point quickly separated, so that the varistor from the circuit excision, and linkage alarm contacts, issued Alarm signal. Because the low melting point of the metal will flow at the point of force and produce cracks, the solder in the low-melting solder joints in the spring tension will flow and create cracks, so the biggest problem with this device is that the solder will age, open.
(3) temperature fuse technology. The technology combines the varistor and the temperature fuse in series, using heat conduction to drain the current on the varistor-generated thermal conduction temperature fuse. When the temperature rises to the set temperature of the temperature fuse, the temperature fuse blows The varistor is removed from the circuit. In addition to the same life and reliability of the temperature fuse, the use of temperature fuses for overheating protection of varistors there are the following questions: heat conduction path is long, the response is too slow, the heat is through a certain heat transfer medium (filling material) The temperature fuse housing, the internal fuse of the temperature fuse, is then passed to the temperature fuse on the melt, thus determining the temperature of the fuse to respond slowly.
(4) isolation technology. The technology will install a varistor in a closed box, isolated from other circuits, to prevent the spread of varistor smoke and flame. In the case of a variety of backup protection failure, isolation technology is also a simple and effective way, but need to take up the equipment space, but also to prevent smoke and flame from the box lead to open the hole come out.
(5) potting technology. In order to prevent the varistor in the failure will smoke, fire and explosion, some manufacturers use the technology to insulate the varistor, but because the varistor in the failure will appear inside the arc, resulting in sealing material failure, and produce Carbon, carbon production will make the arc can be maintained, which often lead to internal short circuit and blackened, and even lead to serious equipment, the entire room blackened. Experiments show that: after the heat shrinkable sleeve of the varistor sleeve, the maximum dissipation power of the varistor is affected by the heat dissipation of the varistor, which affects the power frequency withstand capacity of the varistor. From another angle, Heat dissipation will also accelerate the aging of the varistor, affecting the life of the varistor.
(1) hot melt fuse technology. The technology is to protect the low-melting metal with wax through a certain process installed in the varistor, the varistor leakage current is too large, the temperature rose to a certain extent, low melting point metal fuse, so the varistor from the Circuit excision, can effectively prevent the varistor fire burning. But the thermal fuse there is reliability problems, but also in the environment to strengthen the thermal cycle of only about 5 years of reliable life. In thermal cycling environments, hot melt fuses need to be replaced regularly to maintain normal operation.
(2) the use of spring to pull low melting point solder technology. This technology is currently the vast majority of lightning protection device manufacturers limited pressure SPD technology used in the varistor lead to add a low melting point solder solder joints, and then use a spring to pull the welding point, in the Varistor leakage current is too large, the temperature rises to a certain extent, the welding point of the solder fuse, the spring under the action of the welding point quickly separated, so that the varistor from the circuit excision, and linkage alarm contacts, issued Alarm signal. Because the low melting point of the metal will flow at the point of force and produce cracks, the solder in the low-melting solder joints in the spring tension will flow and create cracks, so the biggest problem with this device is that the solder will age, open.
(3) temperature fuse technology. The technology combines the varistor and the temperature fuse in series, using heat conduction to drain the current on the varistor-generated thermal conduction temperature fuse. When the temperature rises to the set temperature of the temperature fuse, the temperature fuse blows The varistor is removed from the circuit. In addition to the same life and reliability of the temperature fuse, the use of temperature fuses for overheating protection of varistors there are the following questions: heat conduction path is long, the response is too slow, the heat is through a certain heat transfer medium (filling material) The temperature fuse housing, the internal fuse of the temperature fuse, is then passed to the temperature fuse on the melt, thus determining the temperature of the fuse to respond slowly.
(4) isolation technology. The technology will install a varistor in a closed box, isolated from other circuits, to prevent the spread of varistor smoke and flame. In the case of a variety of backup protection failure, isolation technology is also a simple and effective way, but need to take up the equipment space, but also to prevent smoke and flame from the box lead to open the hole come out.
(5) potting technology. In order to prevent the varistor in the failure will smoke, fire and explosion, some manufacturers use the technology to insulate the varistor, but because the varistor in the failure will appear inside the arc, resulting in sealing material failure, and produce Carbon, carbon production will make the arc can be maintained, which often lead to internal short circuit and blackened, and even lead to serious equipment, the entire room blackened. Experiments show that: after the heat shrinkable sleeve of the varistor sleeve, the maximum dissipation power of the varistor is affected by the heat dissipation of the varistor, which affects the power frequency withstand capacity of the varistor. From another angle, Heat dissipation will also accelerate the aging of the varistor, affecting the life of the varistor.
