[2022] What is a Fuse and How Does it Work?

Author: Release time:2022-10-31 Source: Font: Big Middle Small View count:256

As we all know, Edison invented the fuse more than 100 years ago. With the development of the times, the fuse is more and more common in our daily electrical equipment, and its importance is self-evident. Today we will introduce the basic knowledge of fuses to you, welcome to exchange opinions.



1. What is a Fuse?


What is a fuse? It is always known as a current fuse and defined in IEC 127 as a "fuse-link".

 

When a fault or abnormality occurs in a circuit, it is accompanied by a rising current, and the rising current may damage some important devices in the circuit, or burn out the circuit. If the circuit is correctly placed in the fuse, then the fuse will blow itself to cut off the current when the current rises to a certain height and heat, thus it’s important in protecting the safe operation of the circuit.

 

The main function is overload protection. If the fuse is correctly placed in the circuit, it will blow and cut off the current when the current rises to a certain height and heat, thus protecting the safe operation of the circuit.

 

2. Classification of Fuses


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From Shape:


1. Strip wire shape. Early primitive type of fuse, directly locked with screws, used in various sizes of old switches and sockets.

2. Flake (bare flake). Easier to use than the old type of wire.

3. Glass tube. There are several different sizes, commonly used in electronic products.

6.3 x 32 mm (diameter x length)  5 x 20 mm

4. Ceramic tubular. There are several different shapes and sizes, can avoid glass burst.

5. Plastic sheet with metal sheet pins: automotive fuses.

6. Surface Mounted Device (SMD) type.

7. Cylindrical shape, plug-in type: soldered directly on the circuit board, used inside the product.


From Marking:


Marking Most fuses are marked on the body or end caps with markings that indicate their rating.

Fuses may appear similar with significantly different characteristics that identify their markings. Fuse markings typically convey the following information:


  • The amperage rating of the fuse

  • Voltage rating of the fuse

  • Time-current characteristics, i.e., speed of the fuse

  • Approval by national and international standards bodies

  • Manufacturer / Product Number / Series

  • Interrupting Capacity

 

3. How do Fuses Work?

 

Due to the presence of a certain resistance in the conductor, when current flows through it, the conductor will always heat up. The amount of heat generated follows this formula: Q=I2RT; where Q is the amount of heat generated, 0.24 is a constant, I is the current flowing through the conductor, R is the resistance of the conductor, and T is the time for the current to flow through the conductor; according to this formula, it is easy to see the simple working principle of a fuse. When

 

The material of the fuse and its shape are determined, its resistance R is relatively determined (if its resistance temperature coefficient is not considered). When current flows through it, it heats up, and as time increases the amount of heat generated increases.

 

The current and the size of the resistance determine the rate of heat generation, and the construction of the fuse and its installation determine the rate of heat dissipation. The fuse will not blow if the rate of heat generation is less than the rate of heat dissipation. If the rate of heat generation is equal to the rate of heat dissipation, it will not blow in a considerable period of time. If the rate of heat generation is greater than the rate of heat dissipation, then the heat generated will be more and more.

 

And because it has a certain specific heat and mass, the increase in heat is expressed in the increase in temperature, and when the temperature rises above the melting point of the fuse, the fuse blows. This is the working principle of fuse.

 

We should know from this principle that you must carefully study the physical properties of the materials you choose when designing and manufacturing fuses and make sure they have consistent geometry. This is because these factors play a crucial role in the proper functioning of the fuse. Likewise, you must install it correctly when you use it.

 

4. What is the Use of Fuse?


The role of fuse is: when a circuit malfunction or abnormality occurs, along with the rising current, and the rising current may damage some important devices in the circuit, and could cause a fire. If the circuit is correctly placed in the fuse, then the fuse will blow itself to cut off the current when the current rises too height.

 

In the process of using the car, if the electrical equipment does not work, it is possible that the fuse is blown and needs to be replaced in time. The method is:

1. turn the ignition off, then switch and open the fuse box cover. 

2. replace the fuse. Caution:

(1)Replace the fuse according to the rated current value stated on the fuse box cover, do not change to a fuse with higher current than the rated current.

(2)If the new fuse blows immediately, the circuit system may be faulty and should be serviced as soon as possible.

(3)In case of no spare fuse. In case of emergency, you can replace the fuse on other equipment that has no effect on driving and safety instead.

(4)If you cannot find a fuse with the same current load, you can use a lower current rating than the original fuse instead.

 

5. What is the Difference Between a Fuse and a Circuit Breaker?

difference-between-fuse-and-circuit-breaker.jpg

1) Circuit breakers and fuses are both active components, but circuit breakers can achieve line overload protection and short circuit protection, while fuses (fuses) generally can only achieve short circuit protection.


2) From the perspective of short-circuit protection, a circuit breaker with a three-stage LSI protection release (L parameter for overload long-time delay protection, S parameter for short-circuit short-time delay protection, and I parameter for short-circuit instantaneous protection) can achieve complete connection between upper and lower lines. Protection selectivity, while fuses and circuit breakers with two-stage LI protection can only achieve partial selectivity.


3) Compared with circuit breakers, fuses have high short-circuit protection breaking capacity. A fuse can be connected in front to achieve backup protection when the breaking capacity of the circuit breaker is insufficient.


4) The fuse (fuse) has a current-limiting feature, which can limit the short-circuit current and implement line current-limiting protection. General circuit breakers do not have current limiting characteristics, only special current limiting circuit breakers have current limiting functions.


5) As long as the strength of the short-circuit current does not exceed the limit short-circuit breaking capacity, the circuit breaker can continue to be used after the protection action. But the fuse core of the fuse or the fuse must be replaced after the protection action.


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