DC overcurrent protection-where we stand

Most DC systems require some form of overcurrent and/or short circuit protection. As with any fuse selection, the three elements of system voltage, normal load current, and available short-circuit must be considered. For proper application, the fuse´s ratings must equal or exceed the system parameters. Manufacturer´s published data are usually based on AC ratings, and the burden often falls on the user to determine the DC applicability. Furthermore, the manufacturer´s DC test data may not necessarily apply to the DC system at hand. Factors including circuit time constant, voltage, and available short-circuit current may preclude the use of certain DC rated fuses. The procedures used to determine the DC ratings for fuses are addressed. The issues pertinent to insuring a proper DC fuse application are discussed