The basic characteristics of automotive electrical equipment are as follows:
two power supplies
All electrical equipments are connected in parallel with batteries and generators. The generator is the main power supply, which can provide electricity for various electrical equipment when the car is running; the battery is the auxiliary power supply, which is mainly used for starting electricity.
low voltage direct current
As one of the power sources on the car, the battery is always direct current. It is mainly used to supply power to the starter when the engine is started. When the battery is discharged, it must be charged by the direct current power supply. Therefore, the generator on the car must also output direct current.
The rated voltage of the automotive electrical system is generally DC 12V and 24V.
At present, 12V power supply is generally used in automobiles, and 24V power supply is mostly used in heavy-duty diesel engines.
With the increase of electrical equipment in automobiles, the electrical load is getting larger and larger, which requires the use of power sources with large energy and small size in automobiles. At present, some automobile companies are studying the topic of using new 36V and 42V power supplies. From the point of view of efficiency, the use of a 42V voltage system is beneficial to reduce current, reduce energy loss, and can reduce the volume of required electronic equipment and save space.
Two-wire or one-wire in parallel
The electrical equipment on the car adopts a parallel circuit to ensure that the electrical equipment of each branch is controlled independently of each other
The connection between the electrical equipment and the power supply is generally two wires: a common live wire and a common neutral wire.
Single-wire connection means that the positive poles of the electrical equipment on the car are connected to each other by wires and connected to the positive pole of the battery, and all the negative poles are directly or indirectly connected to the metal part of the body through wires, then the metal body of the car body is used as a common wire. Therefore, the purpose of saving wires and electrical circuits is simple, and the installation and maintenance are convenient.
The two-wire system is that in order to ensure the reliability of the electronic control system, modern automobiles require good grounding of the lines, and use special grounding wires to connect electrical components.
Negative ground
The metal body of the car body is used as a common wire. When wiring, a certain pole of the power supply must be connected to the metal body. Such a connection is called grounding. For direct current, the positive or negative pole of the electrical system can be used as the ground pole, but according to the international practice and my country's national standard GB2261-71 "Technical Conditions for Electrical Equipment for Automobiles and Tractors", the vehicle electrical system is the negative pole. iron. The negative grounding can reduce the electrochemical corrosion of the copper terminal of the battery cable at the connection between the frame and the body, and improve the reliability of the grounding.
