The following points shall be observed in practical application of fuses:

First, the protective characteristics of the fuse shall match the overload characteristics of the protected equipment. Taking potential short‑circuit current into account, select a fuse with adequate breaking capacity.

Second, the rated voltage of the fuse shall suit the voltage class of the circuit. The rated current of the fuse shall be greater than or equal to the operating current required for the application.

Third, the rated current of fuse elements at different levels in the circuit shall be properly coordinated; the rated current of the upper‑level fuse element must be higher than that of the lower‑level one.

Fourth, only matching fuse elements complying with specifications shall be adopted. Do not arbitrarily use oversized elements or replace fuse elements with other conductors.

The following factors shall be considered for proper fuse selection:

1. Select fuse models according to circuit requirements and installation conditions. For small‑capacity circuits, semi‑enclosed or non‑filled enclosed‑type fuses are applicable. For high short‑circuit current scenarios, filled enclosed‑type fuses shall be used. Fast‑acting fuses are intended for protection of semiconductor components.

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

3. Determine the fuse rated current based on load characteristics.

4. Fuse elements at successive levels must be selectively coordinated, with lower‑level elements rated at smaller current values than upper‑level ones. Since current values differ for the main gate and each branch circuit, corresponding fuse element ratings shall differ accordingly. In case of a circuit short‑circuit, 15 A and 25 A elements may blow simultaneously, which destroys protection selectivity. This risk can be avoided only when a 2‑ to 3‑level rating difference is maintained between the main circuit and branch circuits.

As an example: the low‑voltage outlet of a transformer adopts RT0‑100/800, while motors use RT0‑400/250 or RT0‑400/350. The ratio of upper‑to‑lower rated current reaches 3.2 and 2.3 respectively, delivering good selectivity. When a short‑circuit occurs on a branch circuit, only the branch fuse blows without interrupting power supply from the main circuit.

5. Avoid undersized fuse elements. An undersized element may cause single‑phase fuse blowing, resulting in motor single‑phase operation and burnout. Statistics show that 60 % of burnt‑out motors stem from improperly configured fuses.