In order to reduce oil dependence, promote energy conservation and emission reduction, promote the leapfrog development of the automobile industry and enhance international competitiveness, my country has classified the development of new energy vehicles as one of the major measures in the transportation sector. At the same time, the compliance of new energy vehicles with relevant standards has also become a major focus of attention. In April this year, the state mandated that newly declared new energy vehicles must comply with EMC national standards. Therefore, the EMC testing of new energy vehicles and their solutions have become an urgent problem for major auto manufacturers and component suppliers.
According to national standards, the EMC of the vehicle generally needs to meet the requirements of GB14023-2011 and GB/T18387-2008.
1. GB14023-2011The vehicle under test required by GB14023-2011 is in two operating modes: "Power on and engine not running" mode and "Engine running" mode.
The "power on and engine not running" mode requires that all electrical equipment on the car are turned on, except that the engine is not running but the switch is turned on, which is equivalent to the vehicle being idle. This state generally does not require the driver to be in the driving position. Use this mode when following the standard average limit.
The "engine running" mode requires the vehicle to run at a constant speed of 40km/hr. This state requires the driver to control and step on the accelerator in the driving position to maintain the vehicle at a speed of 40km/hr. Use this mode when following the standard peak limit.
The standard requires that the position of the test antenna is divided into two directions: horizontal polarization and vertical polarization. Since new energy vehicles are larger than other products in general, the test is usually carried out in a 10-meter darkroom.
Since the test frequency range is from 30MHz to 1GHz, the number of samples generally tested is single, so the standard specifically stipulates that the test result of a single sample is at least 2dB lower than the specified limit. In the laboratory certification test, the limit has generally been lowered by 2dB, so you can intuitively see from the test waveform whether the 2dB margin requirement is reached. On the other hand, according to the standard needs to test the limits of the left and right sides of the vehicle, conditionally test 3 orthogonal surfaces, so according to the standard test, at least 8 sets of results are required.
2. GB/T18387-2008
GB/T18387-2008 specifies the limits of electric field emission and magnetic field emission, and the frequency band is 9kHz-30MHz. The standard requires vehicles to be tested at a steady speed of 16km/hr and 64km/hr.
At the same time, it is necessary to use rod antennas and loop antennas to test the electric field strength and magnetic field strength, and also to test the vertical direction of the electric field and the three orthogonal directions of the magnetic field, and then repeat the test on the four sides of the vehicle. test. Thus, 24 sets of test results were finally obtained.
The factors affecting EMC on new energy vehicles are more complicated, but the specific interference sources can be analyzed from the curve of the test results. Taking different EMC measures for different interference sources can make the EMC solution more economical and applicable and present better results.
Generally speaking, the electronic and electronic control equipment on new energy vehicles may be the interference source of EMC, mainly including motors, motor controllers, main controllers, auxiliary motor controllers (including DC/DC), air conditioners, BMS, chargers , High-voltage power distribution cabinets, console panels, car entertainment equipment, etc., while the corresponding cable routing direction and routing form, improper connection of interfaces or connectors may also become local EMC interference sources.
Before implementing EMC solutions, it is first necessary to determine the frequency band interference source that exceeds the standard based on the results of the pre-scan, and then take measures after finding the interference source.
The basic measures for EMC are shielding, absorption, and grounding.
The essence of shielding is to prevent the interference generated by the interference source from being emitted or conducted out, so that it will not be received by the receiver, thereby reducing the interference limit. In actual processing, it is necessary to determine the holes and seams that may cause leakage, and then reduce the size of the holes; or to prevent the formation of holes when the product is assembled and installed on the electrical connection; in addition, the low impedance loop of the frame can also be used to enhance Shielding effect.
Absorption is to absorb the interference of the interference source nearby so that it will not radiate outward along the wire and space. This will not interfere with internal circuits or external electronic equipment, and can also achieve the effect of reducing the interference limit.
Grounding is to provide an interference low-impedance loop, so that the interference will return to the interference source through a shorter low-impedance path, thereby reducing external interference and lowering the interference limit.
Another type of measure is to deal directly with the interference source itself, which needs to be fully considered at the early stage of the design. Reduce the possibility of interference, so that the interference generated by the product is very small or even does not cause interference. This is the most thorough solution, but it will often lead to a corresponding decrease in performance or an increase in cost. This scheme is generally not suitable for post-processing.
Finally, in order to ensure that the products supplied in batches can also meet the requirements of EMC standards, the overall improvement measures need to be implemented in the design documents to ensure that the products supplied in batches meet the standard requirements. Manufacturers need to negotiate with OEMs how to ensure that the measures are implemented in place during the installation of the vehicle, especially the shielding and grounding measures implemented during the assembly of the vehicle.
Android is an open source mobile operating system based on Linux platform released by Google at the end of 2007, and then improved for use in netbooks and MIDs. The platform consists of operating system, user interface and application software, and is claimed to be the first truly open and complete mobile software for mobile terminals.
To put it simply, the Android system is actually a very open system. It can not only realize the functions of the most commonly used notebook computers, but also realize various directional operations like mobile phones. Moreover, it is specially designed for mobile phones. The operating system developed for equipment has advantages in system resource consumption and human-computer interaction design. It is an operating system that combines traditional and advanced advantages.
New Android Tablet,Android Tablet,New Android Tablet
Jingjiang Gisen Technology Co.,Ltd , https://www.jsgisentec.com