HRC Fuse -Construction, Working, Diagram, Advantages

A fuse is a small wire connected between two terminals that mounted on an Insulating base and connected in series with a circuit. Fuse is the simplest and cheapest current interrupting device used to protect equipment from overload or short circuit faults in medium and low voltage applications. High rupturing capacity fuse is a full form of  HRC fuse. It is reliable and accurate protection for motor and other distribution networks. 

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What is HRC fuse

Definition: HRC fuse is an abbreviation of high rupturing capacity cartridge fuse. In high rupturing capacity fuse, the fuse link carries a short circuit current up to a certain limit. If the limit exceeds the link blow off and it disconnects the faulty circuit. 

It has the advantage over normal rewirable fuse as it has high accuracy and reliable operation. 

HRC fuse normally used to protect distribution systems and electrical motors. HRC fuse diagram is shown below.

HRC-Fuse-working-image


Construction of HRC Fuse

HRC fuse construction is done using the cylindrical body of ceramic material. The fuse element is fitted inside the body and surrounding area filled with pure powdered quartz. 

The two ends of the fuse element are connected to the metal end caps which are screwed to the ceramic body to withstand the pressure developed under short circuit conditions. The contact blade is welded to metal end caps. 

HRC-Fuse-Construction


The fuse element is made of either pure silver or bimetallic material. The fuse element generally constructed with two or more sections of the joint which jointed by means of a tin joint. 

The long cylindrical wire is not used for fuse element because after a short circuit it will melt and will form the string of droplets and an arc will form between each droplet. Later on, these droplets will also evaporate and a long arc will be struck between droplets. 

Due to this tin is used between joint, the purpose of the tin joint is to prevent the formation of long arc during short circuit condition as the melting point of tin metal is low i.e 230 degree as compared to silver fuse element 960 degree. Hence tin melts first under fault condition and prevents the silver link from attaining a high temperature. 

Working Principle Of HRC Fuse

Under the normal working conditions, the HRC fuse link carries a normal rated current, the heat energy developed is not sufficient to melt the fuse element. 

But under short circuit conditions or when the fault occurs, a high fault current starts flowing through the fuse link and it melts before the fault current reaches its first peak. 

As element melts it vaporized and scattered, as arc form the chemical reaction between element vapor and quartz powder, forming high resistance substance which helps in quenching the arc thus fault current interrupts. 

Advantages Of HRC Fuse

HRC fuse has the following advantages:

  • Fast operation
  • Has the capacity of clearing high fault current
  • Not deterioration for a long period 
  • No maintenance
  • Reliable operation
  • Consistence performance
  • HRC fuse is cheaper compare to other circuit breakers

Disadvantages

high rupturing capacity fuse has the following Disadvantages:
  • It required replacement after each operation
  • Interlocking is not possible

Application

Applications of  High rupturing capacity fuse as given below
  • Protection of low voltage distribution system
  • Protection of motor
  • Protection of bus bar
  • Protection of semiconductor devices
  • Use as backup protection to the circuit breaker. 

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