A survey of internal fuses for solid tantalum capacitors

Reasons for fusing solid tantalum capacitors are discussed, stressing that they are only required where there is a low series impedance and a high current availability and where a failed capacitor can overheat due to the fault power dissipation. The two main types of fuses which can be used, i.e. electrically or thermally actuated, are examined. The main advantage of an electrical version is more rapid operation while the advantage of a thermal fuse is lower resistance. As a rough guide the electrical fuse should operate when the fault current reaches 1 amp after 1 second but should survive the initial charging current, which can be tens or hundreds of amps for a very short period. The thermal fuse should prevent the body temperature from exceeding 300°C