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Electrical Course Notes - Unit 2.3.2
High-Breaking-Capacity Fuses
High Breaking Capacity ( HBC ) fuses are suitable for industrial installations and motor starting
circuits. They can distinguish between a starting surge and a short circuit. Their operating
characteristics are such that they can disconnect short circuits much more rapidly than any
other protective device. For example the HBC fuse can clear a high fault current in 0.01
seconds, while the mechanism of a circuit breaker could take 0.1 seconds to operate.
This type of fuse is also known as a High-Rupturing-Capacity ( HRC ) fuse. Its fuse element
is enclosed in a robust cartridge of heatproof material. The cartridge is packed with chemically
treated silica sand to quench the arc which occurs as the fuse element ruptures. This ensures
that there is no fire risk. They do not deteriorate with age.
The construction of a typical HBC fuse is shown in Figure 7.
High Breaking Capacity Fuse
Low Melting
End Cap
Fuse Element
Silica Sand
Fixing Slot
Ceramic Tube
Figure 7
The barrel of the HBC fuse is made from high grade ceramic to withstand the mechanical forces
of heavy current interruption.
The end caps ( tags ) are plated thus ensuring good electrical contact.
The fuse element is accurately shaped and machined to give precise characteristics.
Most HBC fuses are fitted with indicator beads, which show when it has ruptured.
Disadvantages of HBC Fuses
Revision 6, November 2013