Construction of H.R.C. Fuse: Figure shows the essential parts of a typical H.R.C. fuse. It mainly consist of a heat resisting ceramic body. Both the ends of the cermaic body consists of metal end caps. A silver current carrying element is welded to these metal end caps. The current carrying element is completely surrounded by the filling powder which may be plaster of parries, chalk, quartz or marble dust and acts as an arc quenching and cooling medium when fuse element blow off.
Characteristics of HRC Fuse: A Fuse operates when its element melts due to heat produced by I2RF, where RF is Fuse resistance. This heat produced increases if the current flowing through the Fuse element increases. Therefore, we can conclude that a Fuse element will melt faster for large fault current while it will take some time for lower value of fault current. This time-current relationship of Fuse is known as Characteristics of Fuse and is very useful for proper selection of Fuse for a particular circuit and for coordination purpose. A typical Fuse characteristic is shown in figure below.