How to choose a good fuse

(1) UN fuse ≥ UN line.

(2) IN fuse ≥ IN line.

(3) The maximum breaking capacity of the fuse should be greater than the maximum short-circuit current on the protected circuit.

Selection of fuse

(1) Selection of fuse type

The type of fuse should be selected according to the application. The power distribution generally uses knife-type contact fuses (such as HDLRT0RT36 series); motor protection generally uses screw-type fuses; lighting circuits generally use cylindrical hat-shaped fuses; protection is controllable For silicon components, fast fuses for semiconductor protection should be selected.

(2) Selection of fuse specifications

1. Selection of melt rated current

(1) For loads such as transformers, electric furnaces and lighting, the rated current of the European cable joint melt should be slightly greater than or equal to the load current.

(2) For transmission and distribution lines, the rated current of the melt should be slightly greater than or equal to the safe current of the line.

(3) When used as short-circuit protection in the motor circuit, the starting conditions of the motor should be considered, and the rated current of the melt should be selected according to the length of the motor starting time.

For motors with a short starting time, the rated current of the melt can be determined by the following formula IN melt=Ist/(2.5~3)

In the formula Ist-starting current of the motor, unit: A

For motors with a long starting time or frequent starting, the rated current of the melt is determined by the following formula

IN melt=Ist/(1.6~2)

The rated current of the fuse at the main bus bar powered by multiple motors can be calculated as follows:

In=(2.0~2.5)Imemax+∑Ime

Note: the rated current of the In fuse; the rated current of the Ime motor; the rated current of one of the Imemax motors with the largest capacity; the sum of the rated currents of the remaining motors of ∑Ime.

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