Selection of rated voltage of fuse
As a protection device in the circuit, when a fault occurs in the circuit, the fuse work is divided into two processes: “melting” + “breaking”. The process of “melting” is related to the current, and the process of “breaking” is related to the voltage. relation. The voltage of the fuse can be expressed as: This fuse can break the arc generated by this voltage.
The voltage has the difference between alternating current and direct current. In pure electric vehicles, it is a direct current voltage, because the inductance in the loop will generate an induced voltage at the moment when the fuse breaks, and the influence of the inductance in the loop on the voltage arc extinguishing should be considered. The maximum voltage value that the fuse can withstand must be greater than the voltage value in the system. At the same time, there are obvious differences in the breaking of AC and DC fuses. Extinguish the arc; and there is no zero-crossing point in any waveform of the DC current, when breaking the DC short-circuit fault current, the arc is forced to extinguish by the rapid vaporization of the fuse and the diffusion, adsorption and cooling of the quartz sand, so it is more difficult than breaking the AC arc. many.
For the current selection of fuses for electric vehicles, the first step is to consider that the fuse cannot operate during normal operation, that is, the fuse cannot malfunction. This is the starting point and the basic point of the fuse current. Fuse blowing is mainly a process of heat accumulation, and fundamentally, continuous current is the basis for selection.