By EECTECH | 15 July 2020 | 0 Comments
The protection of fuse in electric vehicle circuit cannot be ignored
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 supply system needs to be protected by a high-current fuse to ensure that the main circuit can be cut off in time to avoid damage to the battery. And to prevent accidents such as fires caused by overheating of vehicle lines.
The power supply system mainly includes the battery, power management system and charger. It is especially important to protect the battery from short circuit damage in the power system. When selecting the battery protection fuse, you need to know the following operating conditions to perform the correct Fuse selection:
A) Maximum system voltage
B) The effective value of the current in the main circuit
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 maximum system voltage of most models is generally below 700VDC, and a few models have a slightly higher 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 terminal 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, DC/DC Branch and charger branch.
These 4 branch roads, each branch 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 selection of fuses for these circuit protections, 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 instantaneously. If you follow the general selection method of the fuse 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.
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