Electric vehicle is a high-end industrial product integrating modern high-tech, high electronics, high material technology and manufacturing technology. It relies on power battery to drive and charger to supplement energy. The fuse is responsible for the dual functions of power connection and safety protection in the system, which is related to the overall safety of vehicles and people. Therefore, the fuse for protection of electric vehicle must be a DC type millisecond precision product capable of high-speed disconnection, Otherwise, when the short circuit current occurs, the circuit channel cannot be quickly and safely disconnected, so that the short circuit fault current can directly impact the battery or destroy the IGBT integrated module group of the inverter, and the catastrophic consequences are unimaginable.
After the fuse is connected to the electrical circuit, the fuse is an excellent conductor with low resistance under normal load, only consumes a small amount of electrical energy, and can work stably for a long time under normal power supply conditions. When the overload fault current occurs in the electrical system, the current through the fuse increases rapidly, and the current density through the fuse increases rapidly, resulting in a rapid rise in the temperature in the middle of the fuse. When the temperature reaches the melting point of the fuse, the fuse starts to melt from solid to liquid, and all of the molten metal penetrates into the surrounding quartz sand gap, thus cutting off the fault current in the circuit. The whole process takes about tens of seconds, because the fuse is relatively slow to respond to the overload current, Generally, circuit breakers or thermal relays are used for overload protection.
When there is a huge short-circuit current in the circuit, the current passing through the fuse link increases rapidly in a very short time, resulting in the thin neck of the fuse link directly burning and vaporizing from the solid state in a very short time, generating strong grid arc ion gas, limiting the smooth passage of the short-circuit current, and quickly extinguishing and disconnecting the high-temperature and high-voltage arc bridge under the tight surrounding quartz sand and forced cooling, cutting off the channel of the short-circuit current, and achieving the effect of safe and high-speed disconnection, The whole process takes only a few milliseconds.
Due to its simple operation principle, low manufacturing cost, and strong safety and reliability of limiting the breaking fault current, the fuse is the most effective electrical element for overcurrent protection, especially for short circuit protection. After a long period of continuous use and transformation, it has not been replaced and eliminated by switching appliances, but has been increasingly widely used in modern industry and civil electrical systems.