Fuse is the simplest and cheapest protective device. It is a self sacrificial device used in interrupting the circuit during over- current or short circuit conditions. Fuses are always connected before the load in series to the supply.
Rewirable fuse is also known as kitkat fuse. It is a simple reusable fuse used in the houses, offices and in the protection of outdoor distribution transformers. It is a fully enclosed type fuse and is available in a wide range of ratings. The fuse when blown out can be reused after replacing the fuse element and the circuit can be restored quickly and easily. Renewable fuses are simple in construction and operation but less reliable than HRC fuses.
Read more about fuses
Renewable fuse consists of a base and a separate fuse element carrier made of porcelain. The base consists of two terminals one for incoming supply and the other for the outgoing supply. Similarly fuse carrier also contains two terminals between which fuse element is connected. Usually one or more strands of fuse wires are used as fuse element. The fuse base and the carrier are designed such that each terminals of base coincides with a terminal of the fuse element. The circuit will be closes only if the fuse carrier is inserted into the base and the fuse element is continuous.
The working principle of rewirable fuses is very simple. Whenever the current exceeds the predefined value, the flow of current heats the coil and melts it and the fuse is blown out. Thus the circuit is interrupted.
Once the fuse is blown out, it can be reused by replacing the fuse element with a new one. Fuse carrier is pulled out, blown out fuse element is replaced by a new one and the supply is restored by replacing the fuse carrier in the base. The specialty of renewable fuses is that the fuse carrier can be taken out or reinserted back into the base without risk, even without opening the main switch.
1. Switch of the main switch. (Safety precaution)
2. Take out the fuse element carrier.
3. Loosen the terminal screws and remove the blown out fuse wire.
4. Replace it with a new fuse wire as per the requirement (refer the table below), wrap it around the terminals and tighten the screws.
5. Reinsert the fuse carrier and switch on the main.
The normally used fuse wires are lead and aluminum. Tinned copper and an alloy of tin-lead can also be used. The actual fusing current must be twice the rated current. When two or more fuse elements are used, the wires should be kept apart and a derating factor of 0.7 to 0.8 should be employed to arrive the total fuse rating.
Selection of fuse wire
|Rating||Size of Fuse Wire|
2.0 Mm X 2 Nos.
Standard ratings are 6, 16, 32, 63, 100 and 200 amperes. A fuse wire can have a rating not exceed the rating of the fuse, for example, in a fuse have a rating of 100 A, a fuse wire of any rating not greater than 100 A can be used.
Disadvantages of rewirable fuse
1. Time lag: Due to small time lag, large transient currents which are encountered during the starting of motors and switching on operation of transformers, capacitors, fluorescent lights etc can blow the fuse unless sufficient large rating are used.
2. Low rupturing capacity: Rewirable fuses have limited breaking or rupturing capacity.
3. Slow operation: No feature is employed for extinction of arc that blows after the fuse melts.
4. Risk of flame and fire
5. Single phasing of three phase induction motor is a common occurrence where renewable fuses are employed in motor circuits.
Comparison of rewirable fuses with HRC fuses
Apart from reusability and less cost, HRC fuses are far better in operation and reliability than the rewirable fuse. Because of its simplicity and cheapness rewirable fuses are employed in the protection against short circuit and overload on low and medium voltage circuits only.
Read more on Electric fuse.
- Electric Fuse
Electrical fuse is a simple, less resistive, self sacrificial and cheapest device used to interrupt a circuit under short circuit, excessive overload or over current conditions.
Ezaegu Vincent on November 07, 2020:
I understand it better now because of the detailed explanation. Thanks.
Rajeev krishnankutty on October 22, 2020:
What is the typical breaking capacity(KA rating) of a rewirable fuse?
email@example.com on October 06, 2019:
very true 100A
firstname.lastname@example.org on January 13, 2019:
yeah the site is good
Hebron samwel on September 07, 2017:
I have got more experience about rewireable fuse
CNR on June 21, 2017:
We need to test 100A fuse for breaking current test. Can you please inform the precautions to be taken
Dr le on May 25, 2017:
That great but most engineers prefer to use this because when demage arises easly to replace....
Ali Ruth Mwende on May 15, 2017:
Three main parts of rewirable fuse
Utkarsh on November 20, 2016:
so simple language which is easy to understand. very good explanation.
krishmal on July 28, 2016:
i had done my research and i have found out many things about fuses
DENIS NDUNG\U on January 15, 2016:
Sudarshan on July 20, 2015:
Do you think thr is a limited market for rewireable fuses? We still see people prefering rewireable fuse over MCB, what is the reason for same.
Sky Doctor@naspoly,elect/elect2013-2015 on July 12, 2015:
I Love This Site Because I Got All My Wants Over Here! A Big Cheer To The Owner Of This Site,THANKS
OSBERT JOEL C (author) from CHENNAI on June 15, 2014:
Thank you for your appreciation.
OSBERT JOEL C (author) from CHENNAI on June 15, 2014:
Thank you deepak
Chitrangada Sharan from New Delhi, India on June 13, 2014:
Very useful and informative hub! And your expertise in electrical engineering can be well seen in your hubs.
Thanks for sharing and voted up!
deepak on June 03, 2014:
Very useful. I got all information that I needed. Thankyou