The fuse is an electronic device, which is used to protect circuits from over current, overload and make sure the protection of the circuit. There are many types of fuses available in the market, but function of all these fuses is same.
Fuse consists of a low resistance metallic wire enclosed in a non combustible material. Whenever a short circuit, over current or mismatched load connection occurs, then the thin wire inside the fuse melts because of the heat generated by the heavy current flowing through it. Therefore, it disconnects the power supply from the connected system. In normal operation of the circuit, fuse wire is just a very low resistance component and does not affect the normal operation of the system connected to the power supply.
Types of Fuses:
There are different types of fuses available in the market and they can be categories on the basis of Different aspects.Good to know: Fuses are used in AC as well as DC circuits.
Different Types of Fuses-Fuses can be divided into two main categories according to the type of input supply voltage.
AC fuses
DC fuses
AC and DC Fuses
There is a little difference between AC and DC Fuses used in the AC and DC Systems.
In a DC system, when the metallic wire Melts because of the heat generated by the over current, then Arc is produced and it is very difficult to extinct this arc because of DC constant value. So in order to minimize the fuse arcing, DC fuse are little bigger than an AC fuse which increase the distance between the electrodes to reduce the arc in the Fuse. On the other hand, i.e. in the AC system, voltage with 60Hz or 50Hz frequency changes it amplitude from zero to 60 times every second, so arc can be extinct easily as compared to DC. Therefore, AC fuses are little bit small in sizes as compared to DC fuses.
Fuses can also be categorized based on one time or multiple Operations.
1) One time use only Fuse 2) Resettable Fuses
One time use only Fuse
One time use fuses contain a metallic wire, which burns out, when an over current, over load or mismatched load connect event occur, user has to manually replace these fuses, switch fuses are cheap and widely used in almost all the electronics and electrical systems.
Such types of fuses can be categories on the following basis.
Current carrying Capacity of Fuse
Breaking capacity
I2t value of Fuse
Response Characteristic
Rated voltage of Fuse
Packaging Size
below is the brief explanation of the above categories. Fuse Current Carrying Capacity:
Current carrying capacity is the amount of current which a fuse can easily conduct without interrupting the circuit.
Breaking capacity:
The value of maximum current that can safely be interrupted by the Fuse is called Breaking Capacity and should be higher than the prospective short circuit current.
I2t value of Fuse
The I2t terms related to fuse normally used in short circuit condition. it is the amount of energy which carry the fuse element when the electrical fault is cleared by fuse element.
Response Characteristic:
The speed at which fuse blows, depend on the amount of current flowing through its wire. The higher the current flowing through the wire, faster will be the response time.
Response characteristic shows the response time for over current event. Fuses which respond rapidly to the over current situation is called ultra fast fuses or Fast fuses. They are used in Many semiconductor devices because semiconductor devices damaged by over current very rapidly.
There is another fuse which Is called Slow burn fuse, switch fuses do not respond rapidly to the over current event, but blow after several seconds of over current occurrence. Such fuses found their application in motor control electronics systems because motor takes a lot more current at starting than running.
Rated Voltage of Fuse:
Each fuse has maximum allowed voltage rating, for example, if a fuse is designed for 32 volts it cannot be used with 220 volts, different amount of isolation is required in different fuses working on different voltage levels.
Packaging size:
As we have mentioned above that AC and DC fuses, have a little bit different packaging type, in the same way different application requires different packages to be used accurately in the circuit.other factors and parameters are marking, temperature derating, voltage drop and speed etc.
Other Types of Fuses
Cartridge fuses
Cartridge fuses are used to protect electrical appliances such as motors air-conditions, refrigerator, pumps etc, where high voltage rating and currents required. They are available up to 600A and 600V AC and widely used in industries, commercial as well as home distribution panels.There are two types of Cartridge fuses. 1. General purpose fuse with no time delay and 2. Heavy-duty cartridge fuses with time delay. Both are available in 250V AC to 600V AC and its rating can be found on the end cap or knife blade.
Cartridge Fuses
Blade Type fuses:
This type of fuses (also known as spade or plug-in fuses) comes in plastic body and two metal caps to fit in the socket. Mostly, they used in automobiles for wiring and short circuit protection. to read more about Blade Type of HRC fuses, check this post. Types of HRC Fuses.
Blade Type fuses: used in automobiles
Other Types of Fuses like SMD Fuses , Axial Fuses, Thermal Fuses, HRC (High Rupturing Capacity) fuse and High Voltage fuses ( will discuss latter in detail)
SMD Fuse and Axial fuse
Resettable Fuses:
Resettable fuse is a device, which can be used as multiple times without replacing it. They open the circuit, when an over current event occurs and after some specific time they connect the circuit again. Polymeric positive temperature coefficient device (PPTC, commonly known as a resettable fuse, poly-switch or poly-fuse) is a passive electronic component used to protect against short current faults in electronic circuits.
Application of such fuses is overcome where manually replacing of fuses is difficult or almost impossible, e.g. fuse in the nuclear system or in aerospace system.
Resettable Fuses |Image Credit: Wikipedia
Typical Uses and Applications of fuses:
Electronic Fuses can be used in all types of electrical and electronic applications including:
SMD Fuse and Axial fuse
