Electric Vehicle High Voltage Fuse Applications and Challenges

Currently, Electric Vehicle High Voltage Fuse consists of relatively expensive components (e.g. batteries, power electronics, contractors, etc.). To protect these components from surges and faults, an important aspect of the drivetrain is the proper selection of Fuse (fuse). As EV/HEV electrification solutions continue to evolve and advance, more challenging requirements are placed on fuses.

1 – EV/HEV High Voltage Fuse For conventional industry use protection fuses are generally designed and tested by manufacturers according to published standards IEC60629, UL248 (USA), and VDE0636/0635 (Germany). When introducing high-voltage fuses in EV/HEV, there are currently mainly JASO D622 (Japan) and ISO 8820-7/8 (both applicable to 450VDC, GB/T31465 cited similarly) as well as OEM manufacturing standards. As the new energy vehicle industrialization in the front, standardization in the back, EV/HEV earlier application of high-voltage fuse basically from the traditional industry fuse evolution. Relatively speaking, there are certain differences between automotive-grade high-voltage fuses and traditional industry applications, mainly as follows:

◆ Application environment: traditional industry fuses are mainly based on AC conditions, while EV/HEV is DC voltage;

◆ Cyclic load: EV/HEV current load is difficult to define, depending on vehicle start/stop, driving behavior, etc.;

◆ Ambient temperature: automotive-grade fuses have a more complex ambient temperature profile (high temperature/low temperature) ;

◆Shock and vibration: higher shock and mechanical vibration;

◆Space and weight: automotive grade fuse installation options are more demanding. A fuse is a calibrated current-carrying device. A typical fuse consists of one or more fuses surrounded by a filler (such as silica sand) as an arc extinguishing medium. The fuse style and installation varies from region to region of application, but the fuse structure composition is basically the same, as follows.

Among them, the fuse material, fuse notch configuration, filling material, and processing quality all affect the fuse braking performance. At present, the fuse material of EV/HEV Electric Vehicle High Voltage fuse in the market is mainly silver, and the shape of a fuse can be divided into ribbon and filament to some extent, and changing the cross-section shape can significantly change the fusing characteristics of the fuse. Fuse shell body (material needs to have a certain pressure, temperature resistance) mainly using ceramic (with good thermal conductivity, temperature resistance) or epoxy glass fiber tube (high bending strength, low cost) series. Generally choose quartz sand (with good and stable physical/chemical properties) as a filler (effectively reduce the gas gap in the Fuse), through the filler to provide effective heat transfer, overcurrent breaking when absorbing the arc energy (filler different filling methods affect the arc extinguishing, breaking capacity). Under normal conditions, the fuse carries the current. When a sustained overcurrent occurs, the fuse generates heat at a faster rate than the filler will export the heat, and if the overcurrent persists, the fuse notch will reach its melting point and break. The higher the overcurrent, the faster the fuse melts, i.e., the fuse has an inverse time-current characteristic, which is also an ideal characteristic for protecting conductors and electrical equipment.

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