The type of fuse is mainly selected according to the load and the circuit breaking current. For example, plug-in fuse should be used for the protection of lighting lines with small capacity; For circuits with large short circuit current or occasions with flammable gas, spiral fuse with high breaking capacity or filled closed tubular fuse should be used; For the protection of silicon rectifier devices and thyristor, fast fuse shall be used.
Therefore, we should confirm according to the following basic principles when selecting fuses.
1) Determine the type of fuse according to the service conditions.
2) When selecting the specification of the fuse, you should first select the specification of the melt, and then select the specification of the fuse according to the melt.
3) The protection characteristics of the fuse shall be in good coordination with the overload characteristics of the protected object.
4) In the power distribution system, fuses at all levels should match each other. Generally, the rated current of the upper level melt is 2-3 times greater than that of the lower level melt.
5) For the fuse to protect the motor, attention should be paid to the impact of the motor starting current. The fuse is generally only used as the short circuit protection of the motor, and the overload protection should use thermal relay.
6) The rated current of the fuse shall not be less than the rated current of the melt; The rated breaking capacity shall be greater than the maximum short-circuit current that may occur in the circuit.
