This fuse is used for capacitor banks with a large number of parallel capacitors. It can be used on applications with essentially infinite parallel stored energy, as long as sufficient back voltage can be developed to force the current to extinguish.
Stress specific to the protection of capacitor banks by fuses, which is addressed in IEC 60549, can be divided into two types: Stress during bank energization (the inrush current, which is very high, can cause the fuses to age or blow) and Stress during operation (the presence of harmonics may lead to excessive temperature rises).
The outgoing protection may be HRC fuses, circuit breakers (MCB, MCCB) & SDF (switch disconnector fuse) depending on the rating of the individual capacitor steps, required fault level & customer requirement too. Note: Use switching and protection devices designed for capacitor switching duty.
Most capacitor fuses have a maximum power frequency fault current that they can interrupt. These currents may be different for inductive and capacitively limited faults. For ungrounded or multi-series group banks, the faults are capacitive limited.
The capacitor must be able to absorb this energy with a low probability of case rupture. Fuses are usually applied with some continuous current margin. The margin is typically in the range of 1.3 to 1.65 per unit. This margin is called the fusing factor.
Eaton’s Cooper PowerE series bus-mounted expulsion-type capacitor fuse provides highly reliable, economical protection for capacitor banks where medium-energy-interrupting ability is required. See Table 1 for electrical ratings. The fuse tube is constructed of bone-grade fibre overwrapped with epoxy-bonded filament-wound fiberglass.
Fuse rating for Capacitor Circuits. For the capacitor circuit, the fuse rating is equal to 1.5 times of the full load reactive current by considering staring inrush current, circuit harmonics and capacitor tolerances. The formula will be. Capacitor …