Electric vehicles are mainly composed of three parts: electric drive system, power supply system and auxiliary system. In the main circuit of electric vehicle system, the power system needs to be protected by a high-current fuse to ensure that the power supply can be cut off in time to avoid damage to the battery when the main circuit is short-circuited. And to prevent accidents such as fires caused by overheating of the vehicle lines.
?? The power supply system mainly includes batteries, power management systems and chargers, and it is especially important to protect the battery from damage during a short circuit in the power system. When selecting a battery protection fuse, you need to know the following operating conditions before proceeding. Correct fuse selection:
a) Peak system voltage
b) The effective value of the current in the main loop
c) Overload current and frequency and time of overload
d) The time constant L/R in the entire loop after the fault
e) Expected fault short-circuit current
According to the current fuses used in the electric vehicle industry, the system peak voltage of most models is generally below 700VDC, and there are a few models that are slightly higher than this voltage, so the fuses used for battery protection can be divided into 500VDC and 700VDC. Mainly, the current level is mostly 200A~400A.
There is also a high-voltage distribution box in the main circuit of electric vehicles. Its output is mainly connected to the auxiliary power system of the car. Generally, the inside of the distribution box will include electric heating fan branch, air-conditioning compressor branch, and DC/DC. Branch circuit and charger branch circuit.
Each of these 4 branches needs to install a line protection fuse, the purpose is to cut off the power protection circuit in time when each load is short-circuited to avoid vehicle fires. The fuse selection for these lines, especially the fuse selection of the air-conditioning branch circuit is particularly difficult, because there will be a large starting current inrush when the air-conditioning compressor starts instantly, if you follow the general fuse selection method often When the air conditioner is used normally, the fuse will malfunction and affect the use. Therefore, when selecting the fuse for the air conditioner branch, the overload current must be considered, and an appropriate margin should be left to avoid misselection.
