The Protection Of Fuses in Electric Vehicle Lines 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 the electric vehicle system, the power supply system needs to be protected by installing a high-current fuse to ensure that the power supply can be cut off in time when the main circuit is short-circuited to avoid damage to the battery. And to prevent accidents such as fire caused by overheating of vehicle lines.

The power system mainly includes the battery, the power management system and the charger. In the power system, it is particularly important to protect the battery from being damaged in the event of a short circuit. When choosing a battery protection fuse, it is necessary to know the following operating conditions to carry out the correct operation. Fuse selection:

a) The maximum voltage of the system

b) RMS value of the current in the main circuit

c) Frequency and time of overload current and overload

d) The time constant L/R in the whole 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 there are also 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 the electric vehicle. Its output terminal is mainly connected to the auxiliary power system of the vehicle. Generally, the inside of the distribution box includes the electric heating fan branch, air conditioning compressor branch, DC/DC branch and charger branch.

On these four branches, each branch needs to install a line protection fuse, the purpose is to cut off the power protection circuit in time when a short circuit occurs in each load, so as to avoid the occurrence of vehicle fire. The selection of these fuses for line protection, especially the selection of fuses for air-conditioning branch circuits, is particularly difficult, because a large starting current will flow in when the air-conditioning compressor starts instantaneously. If the general selection method of fuses is used, it is often When the air conditioner is used normally, the fuse will malfunction and affect the use. Therefore, the overload current must be considered when selecting the fuse for the air conditioner branch, and an appropriate margin should be reserved to avoid wrong selection.

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