Low Voltage Fuses Applications

Despite the advancement of re-settable circuit protection devices, fuses are here to stay. In some applications, fuses are irreplaceable particularly in high current limiting or fast fault-current interruption applications.

Fuses offer a combination of advantageous features.

1. High breaking capacity or high current interrupting rating.
2. Complex short-circuit calculations not required.
3. Easy and inexpensive system upgrade to suit increased system fault currents.
4. High current limiting.
5. Fault elimination required before re-energizing circuit.
   Fuses cannot be reset, fault need to be fixed before re-energizing the circuit.
6. Reliability.
   No mechanical parts, fuse replacement ensures protection is restored to its original level.
7. Cost effective protection.
   Compact size offers low cost overcurrent protection at high short-circuit levels.
8. No damage for starters and contactors (type 2 protection - IEC 60947-4-1).
   Current limiting characteristics, suitable for type 2 protection in motor circuits.
9. Safe, silent operation.
   No emission of gas, flames, arcs or other materials when clearing the highest levels of
   short-circuit currents.
10. Easy coordination.
    Standardized fuse characteristics and a high degree of current limitation ensure effective
    coordination.
11. Standardized performance
    Standard fuse-links design and manufactur ensure availability of replacements.
12. Improved power quality.
    Fast fault current interruption minimize dips or sags in system voltage.
13. Tamperproof.
    Fuses cannot be modified or adjusted thus preserving their level of performance and avoiding malfunction.
14. No maintenance.
    Fuses require no maintenance, adjustments or recalibrations.

Table 2 – Fuse application

Type	Application (characteristic)
gG	General purpose
gM	Motor circuit protection
aM	Short-circuit protection of motor circuits
gN	North American general purpose for conductor protection
gD	North American general purpose time-delay
aR	Semiconductor protection
gR, gS	Semiconductor and conductor protection
gU	General purpose for conductor protection
gL, gF, gI, gII	Former types of fuses for general purpose (replaced by gG type)

Source: IEC 60269-5