First, the selection principle of fuse 

1) Determine the type of fuse according to the conditions of use.

2) When selecting the specifications of the fuse, the specifications of the melt should be selected first, and then the specifications of the fuse should be selected according to the melt.

3) The protection characteristics of the fuse should be well matched with the overload characteristics of the protected object.

4) In the power distribution system, fuses at all levels should be matched with each other. Generally, the rated current of the upper melt is 2 to 3 times larger than the rated current of the next melt.

5) For the fuse to protect the motor, attention should be paid to the influence of the starting current of the motor. The fuse is generally only used as the short-circuit protection of the motor, and the thermal relay should be used for overload protection.

6) The rated current of the fuse should not be less than the rated current of the melt; the rated breaking capacity should be greater than the maximum short-circuit current that may occur in the circuit.

Second, the choice of fuse type 

The type of fuse is mainly selected according to the load condition and the size of the circuit breaking current. For example, for the protection of lighting circuits or transfer machines with small capacity, RC1A series plug-in fuses or RM10 series unfilled sealed tubular fuses should be used; for circuits with large short-circuit current or occasions with flammable gas, Use RL series spiral fuses with high breaking capacity or RT (including NT) series sealed tube fuses with packing; fast fuses should be used for the protection of silicon rectifier devices and thyristors. The choice of fuse is mainly based on the protection characteristics of the load and the size of the short-circuit current. For motors and lighting branches with small capacity, fuses are often used as overload and short-circuit protection, so it is hoped that the melting coefficient of the melt is appropriately small. RQA series fuses with lead-tin alloy melt are usually used. For larger-capacity motors and lighting trunks, short-circuit protection and breaking capacity should be considered. Generally, fuses of RM10 and RL1 series with higher breaking capacity are selected; when the short-circuit current is large, RT0 and RTl2 series of fuses with current limiting function should be used.

The rated current of the melt can be selected as follows:

1) When protecting stable loads without starting process such as lighting lines, resistors, electric furnaces, etc., the rated current of the melt is slightly greater than or equal to the rated current in the load circuit.

2) The melt current to protect a single motor that works for a long time can be selected according to the maximum starting current, or can be selected according to the following formula.

The above is the introduction of how to choose the fuse of the car fuse. If you want to know more about the car fuse, please contact us.