Research on Electromagnetic Compatibility of New Energy Vehicles

Transcription

1 2017 4th International Conference on Vehicle, Mechanical and Electrical Engineering (ICVMEE 2017) ISBN: Research on Electromagnetic Compatibility of New Energy Vehicles YUE ZHANG, XU ZHANG, YIFU DING and LI JIANG ABSTRACT The concept of automotive electromagnetic compatibility (EMC) is introduced. The occurrence of electromagnetic interference is pointed out, which includes interference source, transmission path of interference source and interference sensitive equipment. According to EMC test and design issues of new energy vehicles, test items for the development of new energy vehicles are summarized. The methods to enhance EMC performance and the measures to suppress electromagnetic coupling are presented from the perspective of improving vehicle performance. For the vehicle EMC design, some specific advices are given from wires selecting, wire disposal, grounding, etc. The adoption of these recommendations can effectively reduce vehicle electromagnetic radiation and improve the vehicle electromagnetic immunity performance. KEYWORDS EMC, new energy, electromagnetic coupling. INTRODUCTION Nowadays, the application of automotive electronic technology has become an important indicator of the level of automotive technology. 70% of the automotive industry innovation comes from automotive electronic, or closely related to automotive electronics. The statistics show that the cost of electronic components accounted for 20%~30% of the total cost of vehicle in the domestic vehicles and accounted for 30% ~40% of the total cost of vehicle in the foreign high-end vehicles. In this case, to ensure the reliability of a variety of electronic equipments in the vehicle and to ensure the electronic equipments do not interfere with the external equipment has become an important topic of automotive electrical system design. In recent years, new energy automotive industry develops rapidly with the increase in government support. The resulting electromagnetic compatibility problems of the new energy vehicles have been concerned by various vehicle manufacturers and testing organizations. The article sorts out the EMC test items of the new energy vehicle. On this basis, some concrete suggestions and measures are put forward from the point of vehicle EMC design. Yue Zhang, Xu Zhang, Yifu Ding, Li Jiang.China Automotive Technology & Research Center, 68, East Xianfeng Road, Dongli District, Tianjin, China. Yue Zhang, hangyue2016@catarc.ac.cn Xu Zhang, zhangxu@catarc.ac.cn, Yifu Ding, dingyifu@catarc.ac.cn Li Jiang, jiangli2016@catarc.ac.cn 96

2 AUTOMOTIVE EMC CONCEPT The vehicle EMC is defined as the ability of a vehicle or component or an independent technical unit to work satisfactorily in its electromagnetic environment without causing unintentional electromagnetic disturbance to other system in the environment. The electromagnetic compatibility of the vehicle can also be understood as: in the vehicle and its surrounding space, in a certain period of time, in the conditions of available spectrum resources, the vehicle itself and its surrounding electrical equipment can coexist without function degrade or lose. Electromagnetic interference includes three links: interference source, transmission path of interference source and interference sensitive equipment. Interference source In general, interference sources can be divided into two categories:internal interference sources and external interference sources. 1) Internal interference sources The interference sources from the inside of the equipment can be divided into two categories, one is the traditional components, including: wipers, cooling fans, generators, distributors, flashers, electric horns, etc., and the other is the modern components, including: central door lock controller, electronic fuel injection controller, all kinds of electronic modules, all kinds of motors, ECU, SOC and so on. 2) External interference sources There are several interference sources from the outside of the equipment: interference from the nature, such as lightening, cosmic rays, geomagnetic radiation; low-frequency interference from the fluorescent lamp, electric fan; EDM interference from electric drill, electric horn, power switch, motor brush; high-frequency interference from radar and high-frequency transmitter; corona discharge from highvoltage electrical equipment, high-voltage transmission lines and so on[1]. Transmission path of interference source There are three ways to transmit the interference source: (1) Introduce the interference source through the common impedance. The common impedance can be in various forms, such as public power, common ground, signal line and impedance mismatch, etc.; (2)When the interference source is close to a circuit, if the wavelength of the interference source and the distance between the interference source and the circuit meet a certain relationship, the interference will be capacitively or inductively coupled into the circuit; (3) When the interference source leaves a circuit, if the wavelength of the interference source and the distance between the interference source and the circuit meet a certain relationship, the interference will be coupled by far-field electromagnetic radiation. Interference sensitive equipment Various electronic modules, ECU, airbag controller, electronic fuel injection controller, signal cable, etc. are interference sensitive equipment. 97

3 EMC TEST REQUIREMENTS EMC is mainly divided into electromagnetic interference (EMI) and electromagnetic susceptibility (EMS). Electromagnetic interference refers to the performance degradation of equipment, transmission path or system caused by electromagnetic disturbance. Electromagnetic susceptibility means the device or system maintain the original performance when facing electromagnetic disturbance. International Organization for Standardization (ISO), International Electro technical Commission (IEC), and International Special Committee on Radio Interference (CISPR), American Society of Automotive Engineers (SAE), and European Economic Commission (ECE) have developed the relevant technical standards for the electromagnetic interference, see fig. 1. Based on ISO, IEC, CISPR, SAE, ECE and other laws and regulations, our country develops our own standards according to own characteristics. Vehicle EMC standards which are compulsory executed or recommended executed in our country are shown as follows: 1) GB l : Vehicles, boats and internal combustion engine-radio disturbance characteristics-limits and methods of measurement for the protection of off-board receivers. GB is a mandatory standard, which is equivalent to the International Radio Special Committee Standard CISPRl2: The standard is used to protect off-vehicle broadcast receivers from broadband or narrowband radio interference in 30 to 1000 MHz. Revelant experience has shown that it is possible to provide effective protection to the receives in the case of meeting the standard even if the radio transmission frequency are not within the specified range. 2) GB/T Limits and test methods of magnetic and electric field strength from electric vehicles, Broadband, 9 khz to 30MHz. The limits and measurement methods of the electromagnetic field emission strength of electric vehicles or hybrid vehicles are specified in GB/T 18387, which modifies the American Society of Automotive Engineering standard SAE J551-5 Jan GB/T18387provide the protection for off-vehicle receivers in 9 khz~1000mhz coordinate with GBl ) GB/T : Vehicles, boats and internal combustion engines-radio disturbance characteristics-limits and methods of measurement for the protection of on-board receivers. The standard specifies the radio disturbance thresholds and measurement methods in 150 khz to 2500 MHz, which is equivalent to the IEC / CISPR 25: The receiver on the vehicle can be protected from interference caused by modules/systems on the vehicle if the standard is met. The receivers protected are mainly in the following categories: television receivers, terrestrial mobile communications, wireless telephones, amateurs and civilian radio equipment. 98

4 EMC EMI EMS TABLE 1. VEHICLE ELECTROMAGNETIC COMPATIBILITY STANDARDS. Chinese International European SAE Applicable scope standard standard standard standard provide the protection for offvehicle receivers in 9 khz to 30 GB/T18387 MHz GB14023 GB18655 GB/T CISPR12 CISPR25 ISO GB/T ISO ECE R10 SAE J551 SAE J1113 provide the protection for offvehicle receivers in 30MHz to 1000MHz provide the protection for on-board receivers in 150kHz to 2500MHz vehicle immunity to electrostatic discharge vehicle immunity to narrowband radiated electromagnetic energy in10 khz to 18GHz 4) GB/T : Road vehicles-test methods for electrical disturbances from electrostatic discharge. The standard is equivalent to the international standard ISO It specifies the test methods for the electrostatic discharge of electronic modules and systems installed in vehicles, including procedures for evaluating electronic modules in both the bench and the vehicle. All the electrical switches, controllers that can be reached by the driver or passengers and buttons, draw bars, handles that can be used in normal operation need to be tested in the vehicle test. GB and GB/T18387 provide the protection for off-vehicle receivers and GB/T18387 is specifically developed for electric vehicles or hybrid vehicles. GB/T18655 provide the protection for on-board receivers. The above standards are electromagnetic interference standards. GB/T19951 is the electromagnetic susceptibility standard. In addition, there is a clear requirement for the immunity to narrowband electromagnetic radiation energy internationally. The standard ISO specifies the vehicle test method for determining the immunity of passenger cars and commercial vehicles to electrical disturbances from off-vehicle radiation sources in 10 khz-18ghz. The relevant standards are GB/T series in China [2]. EMC DESIGN POINTS The occurrence of any electromagnetic interference must have three basic conditions: interference source, transmission path of interference source and interference sensitive equipment. The interference will happen only when the three conditions are available. The main measure to suppress the interference source is to design the circuit and circuit board carefully, which can control the strength of electromagnetic radiation. For the interference sensitive equipment, methods such as shielding, isolation, filtering, grounding and software processing can be used to improve the antiinterference ability. The above measures are mainly from the point of component design. For the vehicle manufacturers, the main measure is to cut off the transmission 99

5 path of the interference to improve product quality in addition to requiring the parts suppliers to provide qualified products. The transmission path of electromagnetic interference are the following: 1) Current coupling Current coupling is also known as common impedance coupling. It often occurs in the case of the current of two circuits has a common path. The common impedance is divided into common ground impedance and power supply impedance. The common ground impedance is shown in Figure 1. As can be seen from the figure, the operation of device 1 will affect the operation of device 2 due to the presence of the common impedance Z. When the frequency of the circuit is greater than 10 khz, the impedance of Z will increase significantly with the increase of the frequency, resulting in a serious impact on device 2. Making the coupling impedance close to zero can effectively prevent the occurrence of common impedance coupling. 2) Capacitive coupling Capacitive coupling, also known as electric field coupling or electrostatic coupling, is a kind of coupling due to the presence of distributed capacitance, as shown in Figure2. As can be seen from Fig. 2, the high frequency operation of the interference source will induce voltage to the sensor line of the control unit, resulting in the distortion of the sensor voltage. The relationship between the coupling voltage and the operating frequency can be seen from Figure 3. The coupling voltage becomes larger and eventually stabilizes at a constant value with the increasing of frequency. Figure 1. Common impedance coupling. Figure 2. Capacitive coupling. 100

6 Figure 3. Relationship between the coupling voltage and the operating frequency. Figure 4. Inductance coupling. Shorten the wire, increasing the distance between wires, reducing parallel alignment and shielding the interference source and interference sensitive objects can effectively suppress capacitive coupling. 3) Inductance coupling Inductance coupling, also known as inductive electromagnetic coupling or magnetic field coupling, is a kind of coupling due to the internal or external electromagnetic field induction, as shown in Figure 4. Inductance coupling and capacitive coupling have the similar channels and the suppression measures are about the same. The conductor ring subjected to electromagnetic interference should be placed suitably so that the magnetic field lines passing through the ring will be the least. The current loop should be wrapped to a number of local coupling loops, thus the local coupling signal along the length of the wire will cancel each other. 4) Radiation coupling Electromagnetic field radiation can also cause interference coupling, which is a kind of irregular interference. The interference is easily transmitted to the system through the power line. The signal transmission line can radiate interference wave and receive interference wave when the line is long, which is known as large line effect. It will produce resonance especially when the length of the line is an integer multiple of a quarter wavelength, which resulting in the most serious coupling. In the circuit design, the length of the line should be avoided by an integer multiple of the quarter wavelength. The sensor circuit will be subjected to radiation coupling interference produced by the external generator in Figure 5 [3]. 101

7 Figure 5. Radiation coupling. The suppression of radiation-type coupling has three basic forms: electronic filtering, mechanical shielding and interference source suppression. According to the above electromagnetic coupling methods, the following matters need to be noticed in the vehicle design: 1The signal line is separated from the power supply line or meets the minimum distance requirement or is perpendicular to the power line; 2The signal line length is avoided by an integer multiple of the quarter of the guard frequency wavelength; 3Using low resistance wire; 4Avoid interconnection between signal lines; 5The following signal lines are twisted pair: airbag sensor, ABS sensor (wheel speed sensor), bus system (power train CAN, low speed CAN), and diagnostic line, LF signal line (radio to amplifier or speaker); 6The following signal lines are shielded lines: AM / FM HF cable (antenna amplifier to radio), GSM telephone antenna, TV antenna, GPS, navigation system, AUX-In system, USB cable, Bluetooth antenna, PKE antenna, microphone antenna, LCD screen to the radio line (RGB signal); 7Using fiber; 8Using the correct grounding: separate the analog ground from the power ground, digital ground, etc.; ground the interference system; select the correct ground point on the chassis; ground the shielded cable reliably; avoid ring ground connection. CONCLUSION The EMC tests to be done in the vehicle development are discussed and four methods of electromagnetic coupling are analyzed. The problems need to be attentioned in the vehicle design are given, which laid the foundation for improving the EMC capability of vehicles. REFERENCES 1. Liu Yongxi, Shu Chaojun, Li jisan, Hu Yuqing, Jiang Yan, Li Bo, Yu Lei. Analysis for the electromagnetic compatibility of the variable frequency speed control system [J]. Machine Tool Electric Apparatus, 2007, (6):

8 2. Liu Xiaodi, Xie Xiaoping, Zheng Wensheng. Difference between Road Vehicles and Other Types of Electrical/Electronic Products in the ESD Test [J]. Electronics Quality, 2011, (12): Zhu Qianbin, Du Jianfu, Sun Lei, Chen Yanlei. A Study on the Engine Throttle Fault of a Hybrid Electric Bus [J]. Machine Design & Research, 2010, 26(5):