A Car's Power Distribution System Calabration And Matching Investigation Of FAW Car Co., Ltd

With the development of automotive electronic technology, the proportion of electronic components in the vehicle is increasing and the vehicle electrical load is also growing. Auto industry in China in recent years has great progress, but most of them concentrat in the body, powertrain research.For the electrical development ,it is still not enough, especially for the calculation of electrical load .On the one hand because of the automobile platform in China refers to foreign development of a mature platform, on the other hand in people's traditional view, the electrical component is also part of "attachment," not worth the great effort to study them.This provides a variety of electrical faults in the vehicle , especially in recent years, the phenomenon of self-ignition of the car, there is a large part due to an unsuitable design of automotive electrical circuit This article in this context, combinating FAW car company's development process, re-calculats the vehicle electrical power distribution and development process.The order is to sum up a set of effective methods to guide the design.The first task of Auto Electrical Distribution is to collect vehicle with electrical load, and to differentiate between different types of electrical load to form a database as the next design.The first is continous working electrical equipment, that is non-stop work electrical parts in driving cycle, such as engine control unit, a variety of engine control system uses sensors, etc.; The second category is a long-time work system, electrical equipment, this type of electrical equipment under normal circumstances, a longer time to work every time, such as all kinds of lights and lighting, lamp, fan motors, radios, etc.; the other is short-term work system electrical equipment, this type of electrical equipment under normal circumstances, each of the shorter working hours, such as the starter, move window motor, door lock motors.Under normal circumstances, the electricity load is divided into three categories according to importance:Important pieces: including engine control modules (PCM), anti-lock brake system control unit (ABS) and airbag systems control units (SAS) and others involved in vehicle security control unit.As important parts: all kinds of sensors, including the engine, all kinds of warning lights and exterior lights, pre-windshield cleaning device, speakers and so on.Common items include: car audio system, electric heated seats, glove box lighting, electric mirrors, electric windows systems, etc. to cite.Depending on the electrical load, it can begin to define the type of fuse, capacity, quantity, etc. Depending on the load type it can determine the type of fuse,eg MINI or slowly melting; under the current size, to determine the capacity of fuses; electrical circuit according to the amount initially set the number of fuses.Time current characteristic is a measure of an important indicator of fuse fuse characteristics. Fuse with a rated current capacity of continuous flow, but also has more than ratings within the stipulated time and to maintain an effective and reliable off-current off state capacity; melting time depends on the size of the current through the fuse and fuse specifications.Fuse load capacity varies with temperature, in the design must be considered.According to a variety of different loads on board the car's current types are divided into different types: steady-state operating current, pulsed electrical current, operating current surge and so on, different characteristics of each current, we must treat them differently. Calculate fuse rated current depends on the nominal operating current, recommended load for the fuse rated current 75%. Pulse current and surge current and the steady-state currents in different manifestations, can not be directly used as the operating current is based, this paper gives empirical formulas and calculation methods.Then according to the type of fuse, capacity and other information, we can select the different types of wires, there is a very important and confusing concept, the fuse don't protect electrical parts, but the wire, because the electrical parts is easy to replace , while the harness is not easy to replace, in the design of electrical components, you can add the impact on their own circuit.Based on the findings, summarized nine steps to fuse and wire match.1) The calculation of load current loop2) By environmental temperature and the temperature allowed to determine the wire type of wire3) The wire allows current and voltage drop4) The calculation of wire diameter5) from the load current and ambient temperature determine the fuse's rated capacity of6) The calculation of 80℃, rated fuse capacity, verify fuse ability to adapt to the load current7) According to the calculation to determine the capacity of the fuse wire and cross-sectional area8) According to the standard requirements of the current value of checking smoke wire fusing current of Fuse9) Test to confirmAfter the completion of theoretical calculations, but also harness the design according to the actual situation, determine the location and number of fuses. To achieve the purpose of short-circuit protection, you must have the following three conditions.1) fuse close to the power settings.2) The circuit short-circuit current is equal to or greater than the fuse of the fuse current.3) Use upper and lower fuse when the fuse close to the higher power settings, the lower set the size of fuse wire at the junction of specifications.The theory is still immature in china fuse factory , there are still very different for fuse production in foreign suppliers.Therefore, this article has selected the PACE company's fuse parameters as the design basis .For the design of the matching wires, the main reference to the Japanese JASO standards.after matching fuse and wire, it is necessary to plan as a whole for fuse number, that is, there must be a fuse on one circle. Limited to the cost and installation space, the fuse can not be arranged to each power supply circuit , it must only be integrated.This paper analyzes the design of the existing auto insurance problems, and gives an initial solution.Electrical load distribution is a very complicated system engineering, it is more than the design basis vehicle wiring harness, but also a balanced electric vehicle design basis. This is only a preliminary study of this area, follow-up of the calculation and experimental work as well. Is looking forward to China's auto electrical design studies can be had more depth and quality of design for the vehicle to lay a solid foundation.