What is EMC?
EMC is the abbreviation of Electro Magnetic Compatibility in English, which is translated into electromagnetic compatibility in Chinese. In professional terms, it refers to the ability of a device or system to operate in accordance with requirements in its electromagnetic environment and not produce unbearable electromagnetic interference to any device in its environment.
Therefore, EMC includes two requirements: on the one hand, it means that the electromagnetic interference generated by the equipment in the normal operation of the environment cannot exceed a certain limit; on the other hand, it means that the equipment has a certain degree of immunity to the electromagnetic interference in the environment, that is, electromagnetic sensitivity. Is this definition very long and difficult to understand? It doesn't matter! Let me summarize it in a popular sentence: the electromagnetic interference generated by an electronic product itself does not affect other products, and the electromagnetic interference from the outside world does not affect the normal operation of this electronic product. Not interfering with others and not being interfered with by others is the essence of EMC.
It is mentioned above that EMC includes two aspects. One aspect is that the electromagnetic interference generated by the electronic product itself cannot exceed a certain limit. This aspect refers to the content of EMI, which includes four items, namely RE (Radiated Emission) radiation emission, CE (Conducted Emission) conducted emission, HARMonic power supply harmonics, and Flicker voltage fluctuations and flickers.
On the other hand, it means that the electronic product itself has a certain anti-interference ability and will not be interfered by other products. This aspect refers to the content of EMS, which includes seven items, namely RS (Radiated Susceptibility), CS (Conducted Susceptibility), ESD, Surge, EFT (Electrical fast transient/burst immunity test), DIPs (Voltage dips, short interruptions and voltage variations), and PMF (Power Frequency Magnetic Field Immunity).
EMC interference forms
Generally speaking, there are only two interference paths for EMC, one is conducted emission through cables, and the other is radiated emission through space. Although there are only these two interference paths, each EMC project will have its own unique interference form. The interference forms of the four EMI projects are as follows:
Radiated emission propagates through space. For the current inverters in the industry, the main frequency range is 30MHz~1GHZ.
Power harmonics propagate through power lines. For the current inverters in the industry, the main frequency range is 50Hz~9KHZ.
Voltage fluctuations and flickers propagate through power lines.
Conducted emission can be propagated through power lines, network cables, RS485 communication cables and other cables. For the current inverters in the industry, the main frequency range is 150KHz~30MHZ.
The interference forms of the seven EMS projects are as follows:
Lightning surge: voltages of up to tens of thousands of volts or even hundreds of thousands of volts are instantly applied to various outgoing cables of the inverter.
Electrostatic discharge: Electrostatic voltages of up to thousands or even tens of thousands of volts are applied to the inverter instantly.
Radiated interference resistance: For the inverter products in the industry, the frequency ranges from 80MHz to 2.7GHz, and the voltage field of up to ten volts or even tens of volts per meter is applied to the inverter.
Fast transient pulse group: Several thousands of volts of transient high voltage are continuously applied to various outlet cables of the inverter at a repetition frequency of 2.5KHz or 5KHZ.
Conducted interference resistance: The frequency ranges from 0.15MHz to 80MHz, and the voltage to the ground of up to several volts is applied to various outlet cables of the inverter.
Power frequency magnetic field: The frequency is 50Hz/60Hz, and the field strength of several amperes per meter is applied to the inverter through space.
Voltage drop: The voltage supplying the equipment has interference such as voltage drop, voltage surge, and short-term power outage.
Dangers of EMC
The hazards of EMC need to be considered from two aspects. The first is the hazard of EMI, and the other is the hazard of EMS, because these two hazards are different aspects. EMI interferes with other products, causing other equipment and systems to degrade in performance, fail to work, or even be damaged. The main manifestations are as follows:
EMI interference causes communication failures and interruptions in other equipment
EMI interference causes other equipment to fail to work or even be damaged.
EMI interference causes power grid protection devices to malfunction or refuse to operate, leading to power grid accidents
EMI interference causes other product systems to "crash"
EMI interference affects human health
Perhaps many inverter customers have encountered or heard similar experiences: after installing a photovoltaic inverter at home, the channels that used to be clear when listening to the radio at home now have a lot of squeaking noise, and even some radio stations I can’t receive it anymore. Some inverter users say that the electronic clock at home is not accurate. Some inverter users say that TV images sometimes have spots, flickers and other abnormal phenomena. These are actually EMI interference from the inverter. Phenomenon.
In addition to the EMI phenomena caused by these inverters, there are actually many phenomena related to EMI in our lives. For example, when we often listen to songs on the stereo, if a call comes from the mobile phone, the stereo will make a creaking sound. In fact, In the early days, airlines generally stipulated that they were not allowed to answer mobile phone calls while flying on civil aircraft, mainly because they were afraid that mobile phone signals would interfere with the normal communication of the passenger plane and cause the plane to crash. Of course, with the development of EMC technology, many passenger planes have solved this problem. Due to the problem of mobile phone interference, this requirement is no longer implemented, but our domestic airlines are still implementing this requirement. Having said this, many friends may be worried, should they stop using mobile phones in the future? In fact, as long as mobile phones are used rationally, this worry is unnecessary.
Because mobile phones emit large amounts of radiation only during calls. If the mobile phone is in standby mode, the radiation is actually very low. If you are still worried, you can take some protective measures for yourself, such as wearing radiation-proof clothing. In fact, you often see many pregnant women wearing radiation-proof clothing around you. This is a good measure. It can shield a lot of radiation. Large portion. Speaking of radiation protection clothing, here is a simple way to tell whether it is good or bad. This is to wrap the mobile phone in radiation protection clothing and see if the mobile phone signal is reduced. If the mobile phone signal is still full after being tightly wrapped in radiation protection clothing, If the cell phone signal is low, it means that the radiation protection suit is very effective.
The phenomenon of EMI interference often occurs not only in civilian use, but also in the military, and the military also deliberately strengthens EMI interference. Perhaps you often listen to the news and read newspapers, and you can often hear news that a certain army is operating under complex electromagnetic interference. Conducting electromagnetic confrontation exercises in a complex electromagnetic environment, or performing a certain task in a complex electromagnetic environment, is actually using EMI to interfere with the communications of the opponent's army, making it impossible for the opponent's army to command and communicate, thereby gaining an advantage and winning the war.
EMC Control
It is precisely because EMC is so harmful that relevant laws and standards have been formulated at the international, national, and SMA China levels to restrict the EMC of products.
Among them, the laws and standards promulgated at the international level are:
IEC 61000-6-1, IEC 61000-6-2, IEC 61000-6-3, IEC 61000-6-4,CISPR 11……
The laws and standards promulgated at the national level are: NB/T 32004
The standards promulgated at the company level are: "SMA China EMC Standard"
Although the international, national, and even company levels have their own standards, the national standard requirements are basically the same as the international standard requirements. The only difference is that the "SMA China EMC Standard" is stricter than the international and national standards.
Severe test
It is precisely because SMA China has high standards that a high-standard test platform is needed to support the high standards. SMA China has invested a lot in EMC test equipment, built its own conduction laboratory, and shared the resources of SMA EMC laboratory with the world-class EMC laboratory - SMA China. At the same time, SMA laboratory strictly controls the quality of SMA China's products! Ensure that the products put on the market meet all EMC requirements.
Conclusion
EMC is closely related to our lives. Many problems or phenomena encountered in life are caused by EMC. Those products that do not meet the EMC standards will only do evil in people's lives, causing inconvenience to people's lives, causing losses to people's property, and causing harm to people's health. The victims will only be the majority of consumers. So we advocate: Please pay attention to EMC, our interests, and our personal safety!
