(1) The protection characteristics of the fuse and the overload ability of the object to be protected should be matched so that the protected object can be reliably protected in the whole range.

(2) should prevent leapfrog, so as not to enlarge the scope of the accident, fuse should be coordinated between the various levels, when the failure,The lower fuse should first fuse, and after the lower fuse fuse, the superior fuse can automatically recover.

(3) In the distribution system with low short-circuit current and high failure rate, the fuse with convenient disassembly and disassembling melt should be preferred.

(4) In the distribution system with a large short-circuit current, the fuse with high breaking capacity should be selected, and if necessary, the flow-limiting function is better Fuse. However, special attention should be paid to the limited flow of the fuse, nor under any circumstances can limit the flow.

(5) for motor overcurrent protection of the fuse, generally do not require a finite flow, can be selected with zinc melt or lead-tin alloy Fuse for melt.
Determination of the rated current of melt

(1) Lighting circuit. The fuse rated current ≥  is protected by the sum of all lighting electrical work current on the circuit.

(2) motor.、

(1) single-Station direct starter motor. Fuse rated current = (1.5-2.5) x electric machine rated current.

(2)multiple sets of direct starter motors. Total protection Fuse Rated current = (1.5-2.5) x the sum of each motor current.

(3) Decompression starter motor. Fuse rated current = (1.5-2) x electric machine rated current.

(4) Winding type electric machine. Fuse rated current = (1.2-1.5) x electric machine rated current.

(3) Low voltage side of distribution transformer. Fuse rated current = (1.0-1.5) x transformer low voltage side rated current.

(4) Shunt capacitor group. Fuse rated current = (1.3-1.8) x capacitor Group rated current.

(5) Welding machine. Fuse rated current = (1.5-2.5) x load current.

(6) Electronic rectifier components. Fuse rated current ≥1.57x rectifier element rated current.