Design and Manufacturing of HRC Fuse Links

 
This report consists of design, manufacturing process and other considerations to be taken care during manufacturing of HRC Fuse links. This task is assigned by Dr. KVSSN Rao, faculty member, National Institute Of Industrial Engineering. This is a design and some suggestions for conservation on preliminary basis. All the suggestions are invited to make this report better and knowledgeable.
 

Fuse Link

Introduction:
 
HRC fuse link is a very common, simple and effective electrical protection device against over load and short circuit current. It consists of fuse wire which is designed according to the customer's requirement and the rest of the design depends upon it. Whenever high inrush of current takes place, the fuse wire gets heated mush and melts thereby cutting the supply and preventing any damage to the equipments. Now, what we need to design is the rated current of the circuit where it shall be installed. Then, we shall find it's breaking capacity which determines how fast the fuse shall blow off.  It is so simple device that even an un-skilled person can handle it. In this report we shall discuss regarding the HRC fuse link of rating 500V.
 
Market Potential:
 
Every electrical equipment, factory, shops, offices etc. need electrical protection devices for smooth running. HRC Fuses are the reliable and cheap option to prevent loss of equipment due to overloads. Circuit breakers, are  nothing but the larger version of fuse and they are advanced since they need to bear much higher voltage and hence the surge  which is generated when the connection is broken us huge compared to fuse. Both fuse and the circuit breakers operate on the principle of inverse square law which says that higher the current lower the time taken to break the circuit. Because of massive rural and urban electrification programmes of Government, there is a good demand for this product. This product is available in a wide range of rated capacity as per customer's requirement .
 
Specification of fuse
 

3NA7 LV HRC Fuses

Standards

IS 13703 Part 2 Section 1(1993); IEC 269

Dimensions

IS 13703; IEC 269

Rated Voltage

AC 500V / DC 440V upto 630A (DC 250V for size 00)

Rated Current Range

2 to 800A: (500 Vac) 800A@415V

Rated Breaking Capacity

AC 120kA / DC 25kA

Mounting position

as desired but preferably vertical

Resistance to climate

-300 C to +500 C at 95% relative humidity

Design of HRC fuse

Operating Voltage=440V dc

Breaking capacity=25kA

Hence, the resistance required= V/I=440/25k=0.0176 ohms

R=ϱ.l/A

R= minimum resistance of the fuse required

ϱ -resistivity of copper

l-length of fuse

A=area of fuse

A=(3.14157)*r2/4

p=1.678*10-8Ům
 
Let the length of fuse be 170mm

Hence, l=0.170m

A=ϱ.l/R

A=(1.678*10-8)( 0.17)/(0.0176)

A=1.62*10-7m2

A=0.162mm2

Now, A=(3.14157)*r2/4

r2=A*4/(3.14157)

r2=0.162*4/(3.14157)

r=0.454mm
 
 
Basis and Presumptions
 
i.  The design of the fuse wire has been done and the length of the case and width have been assumed  suitably
 
 ii. The rated breaking capacity of the current has been provided
 
Implementation Schedule

The major activities in the implementation of the project has been listed

Activity

1. Preparation of project report

2. Registration and other formalities

3. Sanction of loan by financial instructions

a) Placement of orders

b) Procurement

c) Power connection/ Electrification

d) Installation/Erection of  machinery/Test Equipment

5. Procurement of raw materials

6. Recruitment of Technical Personnel etc.

7. Trial production

8. Commercial production

 

Notes

1. Many of the above activities shall be initiated concurrently.

Process of Manufacture

The final product HRC Fuses link is basically assembly of electrical conducting and insulating components. The design of HRC Fuses link depends upon rating of current and voltage to be handled. The components like Fuse element are usually designed according to customer's requirement. Other components like blades, ceramic barrel, ceramic base plate, silica gel, end cover, blown up indicating and striking device and brass hard ware etc. are bought out components. In the above design the design for the fuse element has been shown.

All the components as discussed in above paragraph are fixed at ceramic housing called barrel and contact blade for connection to be made on it. Complete assembly put on testing bench for final testing to set accuracy of the HRC Fuses link. The routine test to be carried out at every stage of assembly. Final product to be tested as per relevant IS Specification.

Quality Control and Standards

Low Voltage Fuses for voltages not exceeding 1000 V A C or 1500 V D C. (HRC FUSE LINKS), IS 13703:1993.

Energy Conservation 
 i. With the growing energy needs and shortage coupled with rising energy cost, a greater thrust in energy efficiency in industrial sector has been given by the Government of India since 1980s.
ii. The following steps may help for conservation of electrical energy: 
iii. Adoption of energy conserving technologies, production aids and testing facilities.
iv. Efficient management of process/manufacturing machineries and systems and testing equipments for yielding maximum Energy Conservation. 
v. Optimum use of electrical energy for heating during soldering process can be obtained by using efficient temperature controlled soldering and de-soldering stations. 
vi. Periodical maintenance of motors, compressors etc. 
vii. Use of power factor correction capacitors. Proper selection and layout of lighting system; timely switching on-off of the lights; use of compact fluorescent lamps wherever possible etc.

 References

[1] Specific resistance, retrieved from http://www.allaboutcircuits.com
[2] Electric Fuse, retrieved from en.wikipedia.org
[3] HRC fuses, retrieved from http://www.eevblog.com
[4] Pre-arcing behaviour of open fuse wire, retrieved from http://iopscience.iop.org
[5] Copper wire, retrieved from http://www.epanorama.net
[6] Resistivity of copper, retrieved from http://www.hypertextbook.com
[7] Fuses HRC, retrieved from http://www.transpower.net.in
[8] HRC Fuse Links, retrieved from http://www.dcmsme.gov.in

Darga Vasavi (Roll No. 31), Kapil Verma (Roll No. 43), Mohan Singh Dhaked (Roll No. 57),

Post Graduate Diploma in Industrial Engineering, National Institute of Industrial Engineering, Mumbai, India

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