Working principle of vehicle fuse
Vehicle fuse is usually called fuse. The matching design of fuse is an important part of the principle design of the whole vehicle, including the selection of fuse type, capacity, fuse path, fuse sharing, and a series of contents. This paper mainly introduces the system selection method of fuse.
Understanding the working mechanism of fuse is the premise of correct fuse matching design. To fully understand the working mechanism of the fuse, only two questions need to be understood: 1. Why should the fuse be added in the circuit and 2. How does the fuse protect the circuit.
Why should we fuse the circuit?
If there is no fuse in the circuit, the current in the circuit will inevitably increase once the circuit is overloaded or short circuit occurs, so when the current flowing through the wire exceeds the carrying current of the wire, the wire will overheat, melt the wire insulation layer and copper wire, and even spontaneous combustion will occur, leading to safety accidents (car burning). The natural phenomenon of the conductor is shown in the figure below:
After finding out the causes and consequences of wire self-ignition, we should ask how to avoid the problem of wire self-ignition?
The fuse is generated in such a situation. In order to avoid the spontaneous combustion of the wire, we hope that a component can detect the overcurrent and short-circuit current in the circuit before the wire burns, and can react quickly, and can quickly interrupt the circuit (fuse fuse), so as to achieve the purpose of protecting the wire.
Such a component that protects the wire in the circuit is what we call fuse, or fuse. The fuse is a thermal response device, which is designed and manufactured to protect the wiring harness and is the weakest part of the circuit. It is an electrical component to protect the wire. It is worth mentioning that in the circuit, the fuse can only protect the wire behind the fuse, so the fuse should be set close to the power supply as far as possible, as shown in the figure below. If the distance is too far, we need to consider setting up a higher level of insurance.
How does the fuse protect the circuit and what is the working mechanism of the fuse?
After understanding why the fuse should be added in the circuit, we have a clear understanding of the working mechanism of the fuse. Understanding the main function and working mechanism of the fuse is very important for the matching design of the fuse.
The working mechanism of the fuse is that when the circuit is short-circuited, the fuse can be blown in time when the wire smokes and catches fire, so as to cut off the circuit, prevent the wire from burning and cause the vehicle to ignite.
The specific working principle of the fuse is as follows:
The fuse has a certain resistance, and the conductor will generate heat when flowing through the current. The heat will increase with time, and the current and resistance will also increase the heat generation speed. The structure and installation of the fuse determine the heat dissipation speed.
If the heat generation speed is less than the heat dissipation speed, the fuse will not blow;
If: heat generation speed=heat dissipation speed, it will not fuse in a long time;
If: heat generation speed>heat dissipation speed, heat accumulation, when the temperature rise reaches above the melting point of the fuse, the fuse will blow.
This is how the fuse works.
In the circuit design, the fuse is connected to the power supply side of the circuit. When the load is over-current, the device or wire is short-circuited, the heat generated by the current reaches the melting point in the part with a small cross-section of the fuse, which protects the wire of the circuit. The following figure is the schematic diagram of the fuse fusing process.
