The following points shall be noted for fuses in practical operation:

First, the protective characteristics of the fuse shall match the overload characteristics of the protected equipment. Fuses with adequate breaking capacity shall be selected with prospective short‑circuit current taken into account.

Second, the rated voltage of the fuse shall comply with the voltage class of the circuit. The rated current of the fuse shall be greater than or equal to the rated current of its fuse‑link.

Third, proper coordination shall be achieved among the rated currents of fuse‑links at different levels in the circuit. The rated current of the upstream fuse‑link must be higher than that of the downstream one.

Fourth, matched fuse‑links specified for the fuse shall be adopted. It is forbidden to arbitrarily enlarge the fuse‑link rating or replace the fuse‑link with other conductive materials.

The following factors shall be considered for proper fuse selection:

1. Select fuse models according to circuit requirements and installation conditions. For low‑capacity circuits, semi‑enclosed or non‑filled enclosed fuses are applicable; filled enclosed fuses are used for circuits with high short‑circuit current; fast‑acting fuses are deployed for the protection of semiconductor components.

2. Select the rated voltage of the fuse in accordance with circuit voltage.

3. Select the rated current of the fuse based on load characteristics.

4. Fuse‑links at different levels shall be selectively coordinated, with downstream ratings lower than upstream ones. Fuse selection differs for main switches and branch circuits due to varying current magnitudes. Improper coordination may cause simultaneous blowing of 15 A and 25 A fuse‑links upon circuit short‑circuit and result in loss of protection selectivity. Such failure can be avoided by maintaining a 2‑ to 3‑level rating difference between the main switch and branch circuits. For instance, RT0 100/800 is adopted for the low‑voltage outlet of a transformer, while RT0 400/250 or RT0 400/350 are applied for motors. The upstream‑to‑downstream rated‑current ratios reach 3.2 and 2.3 respectively, ensuring good selectivity. In case of a branch short‑circuit, only the branch fuse blows without interrupting power supply from the main switch.

5. Avoid undersized fuse‑links. An undersized fuse‑link may lead to single‑phase blowing, which causes motor damage under single‑phase operation. Statistics show that 60 % of burnt‑out motor failures stem from improper fuse configuration.