The filling material may be chalk, plaster of paris, quartz or marble dust and acts as an arc quenching and cooling medium. The space within the body surrounding the element is completely packed with a filling powder. It consists of a heat resisting ceramic body having metal end-caps to which is welded silver cuirent-carrying element. 20.3 shows the essential parts of a typical H.R.C. High-Rupturing capacity (H.R.C.) cartridge fuse: The primary objection of low and uncertain breaking capacity of semi-enclosed rewireable fuses is overcome in H.R.C. Therefore, the use of this Types of Fuses is limited to domestic and lighting loads.Ģ. Semi-enclosed rewireable fuses are made up to 500 A rated current, but their breaking capacity is low e.g., on 400 V service, the breaking capacity is about 4000 A. Accurate calibration of the fuse wire is not possible because fusing current very much depends upon the length of the fuse element.The protective capacity of such a Types of Fuses is uncertain as it is affected by the ambient conditions.Therefore, after some time, the current rating of the fuse is decreased e., the fuse operates at a lower current than originally rated. The fuse element is subjected to deterioration due, to oxidation through the continuous heating up of the element. This type of fuse has a low-breaking capacity and hence cannot be used in circuits of high fault level.There is a possibility of renewal by the fuse wire of wrong size or by improper material.Secondly, the cost of replacement is negligible. Firstly, the detachable fuse carrier permits the replacement of Types of Fuses element without any danger of coming in contact with live parts. The fuse carrier is then reinserted in the base to restore the supply. The fuse carrier is taken out and the blown out fuse element is replaced by the new one. When a fault occurs, the fuse element is blown out and the circuit is interrupted. The fuse carrier can be inserted in Of taken out of the base when desired. The fuse carrier is also of porcelain and holds the Types of Fuses element (tinned copper wire) between its terminals. The base is of porcelain and carries the fixed contacts to which the incoming and outgoing phase wires are connected. It consists of (i) a base and (ii) a fuse carrier. Semi-enclosed Rewireable fuse: Rewireable fuse (also known as kit-kat type) is used where low values of fault current are to be interrupted. High rupturing capacity (H.R.C.) cartridge fuse.ġ.Low voltage fuses can be subdivided into two classes viz., If such means of isolation are not available, the Types of Fuses must be so shielded as to protect the user against accidental contact with the live metal when the fuse carrier is being inserted or removed. It is a usual practice to provide isolating switches in series with fuses where it is necessary to permit fuses to be replaced or rewired with safety.
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