Precautions for Fuse Field Application
Several key points deserve attention during on‑site use of fuses:
First, the fuse’s protection characteristics shall align with the overload behaviour of protected equipment. Select fuses with sufficient breaking capacity by taking prospective short‑circuit current into consideration.
Second, the fuse rated voltage shall match the circuit voltage level. Its rated current shall be no less than the rated current of the installed fuse‑link.
Third, current‑rating coordination must be implemented for fuse‑links at different circuit tiers. The upstream fuse‑link shall always carry a higher rated current than the downstream one.
Fourth, only original matching fuse‑links shall be fitted. Never over‑specify fuse‑links or substitute them with other conductive materials.
The below factors shall be taken into account when selecting fuses:
Determine fuse models based on circuit requirements and installation conditions. Semi‑enclosed or non‑filled enclosed fuses suit low‑power circuits; filled enclosed fuses apply to circuits with high short‑circuit current; fast fuses are designated for semiconductor component protection.
Match the fuse rated voltage to operating circuit voltage.
Choose fuse rated current according to load characteristics.
Tiered coordination is required among fuse‑links, with lower‑level ratings smaller than upper‑level ones. Main switches and branch circuits carry different currents and thus require different fuse‑link specifications. Poor coordination may cause both 15 A and 25 A fuse‑links to blow simultaneously under short‑circuit conditions, eliminating protection selectivity. This risk can be avoided by maintaining a rating gap of 2‑3 tiers between main switch and branch circuits. For example, RT0 100/800 is used for transformer low‑voltage outlets, while RT0 400/250 or RT0 400/350 are adopted for motor circuits. The upstream‑downstream rated‑current ratios stand at 3.2 and 2.3 respectively to secure reliable selectivity. When a short‑circuit occurs on a branch circuit, only the branch fuse‑link operates, leaving the main power supply intact.
Avoid under‑rated fuse‑links. Undersized ratings risk single‑phase fuse‑link blowing, which results in motor burnout due to single‑phase running. Statistics indicate that improper fuse configuration accounts for 60 % of burnt‑out motor incidents.