Fuses are active components primarily used for overload and short circuit protection in low-voltage distribution networks and control circuits. They can also be used for overload protection of cable conductors and protection of power electronic components. A fuse consists of a fuse base and a fuse (fuse element).

Dc Fuse
When a fuse wire is connected in series in a circuit, the temperature of the fuse rises to the melting point of the fuse wire (or fuse strip) during overload or short circuit conditions, causing the fuse wire to melt rapidly and thus interrupting the circuit. To effectively control the melting point at the thinnest part of the fuse wire, tin beads are welded onto it. The metallurgical effect formed by the melted tin bead and copper fuse wire reduces the melting point, obtaining a controllable fuse temperature, thus achieving the reverse DC fuse time-limit line protection characteristics.
To effectively eliminate metal vapors and explosive gases, quartz sand filler is used inside the fuse body for effective arc extinction. Sometimes, closed tubular fuse bodies without fillers are used, relying on the pressure generated at high temperatures to extinguish the arc. Fuses have a high breaking capacity and reliability, are easy to maintain, and are relatively inexpensive, hence their widespread use in low-voltage distribution networks.

 

Dc Combiner Box Components

Working Principle of Photovoltaic DC Fuses: Metal conductors, serving as the fusible element, are connected in series in the circuit. When overload or short circuit current passes through the fusible element, it melts due to its own heat, thereby interrupting the circuit. Fuses are simple in structure, easy to use, and widely used as protection devices in power systems, various electrical equipment, and household appliances.

Determination Of The Melting Point Of The Fuse

If it is uncertain whether the parts of a DC fuse will be adversely affected by temperature and sealing force, the following tests should be conducted:
1. Test Setup. Install a simulated fusible element onto the photovoltaic DC fuse base and hang it on the measuring device. The fixing method of the simulated fusible element on the photovoltaic DC fuse base (such as using a clip) should not significantly affect heat dissipation. The conductor load area and rated current values are related to Table 10 in GB13539.1-2002. The length of the wire outside the oven should be at least 1m. The measuring device should be installed in an oven of at least 50L volume or placed under a heating hood. Note the casing of the measuring device and connecting wi         res. During the test cycle with and without test current, the oven temperature should be maintained at (80+5)℃, measuring temperature at a horizontal distance of 150mm from the center point of the simulated fuse, related.2. Test Method. After the oven temperature is raised to (80+5)℃ and maintained for 2 hours, the simulated fuse is to carry 160% of the rated current for 2 hours, with a current tolerance of ±2%. The test can be conducted at reduced voltage. 3 minutes after the current is applied, a smooth force Fmax is applied to the simulated fusible element. The force is maintained for 15 seconds.
3. Judging the Test Results. After testing, the displacement of the contacts on the photovoltaic DC fuse base should not affect the continued use of the photovoltaic DC fuse base. After removing the simulated fuse, measurements should be taken. The insulation layer of the photovoltaic DC fuse base should not crack or show any cracks.

Dc Fuse Base Testing

Conclusion
For all DC applications it is absolutely necessary to define the fuse with:
1.The voltage
2.The time constant of the circuit
3.The fault currents
It is required as well to get all necessary information about the rated current passing in the fuse as well as the load cycles and overloads to withstand in order to calculate the current rating of the fuse so that its life time fits with the life time of the equipment it must protect.