Electromagnetic compatibility requirements and testing methods for AC regulated power supplies
1 Basic concepts
Electromagnetic compatibility is an important quality indicator for electrical and electronic products. It can be considered that product quality mainly consists of two main components: quality specifications and technical indicators. The former involves general specifications, namely international IEC, and domestic basic standards formulated by the state; The latter is the regulation of product functions and their technical requirements. Basic standards for electromagnetic compatibility. Now EMC has formed a complete system from basic standards, general standards, family standards, to product standards. In addition, there is specialized legislation internationally for this purpose. As the European Union has formulated regulations, starting from January 1, 1996, electrical and electronic products must obtain low-voltage management (LV Directive) and electromagnetic compatibility management (EMC Directive) certification before they can be sold in the market. In recent years, new EMC standards have been officially released in China. However, it should be pointed out that IEC related EMC standards will continue to be upgraded from draft or old versions to official versions, and national related EMC standards will also be continuously updated and released. EMC testing should be based on the new version.
The so-called EMC is defined in GB/T4365-1996 "Electromagnetic Compatibility Terminology" as the ability of a device or system to operate normally in its electromagnetic environment without causing unbearable electromagnetic interference to anything in that environment. This definition summarizes three aspects of content. Firstly, the limitation of electromagnetic interference. Electromagnetic interference is common, but its harmfulness can be limited by quality standards and technical means. This means that the product should have a limit value for the intensity of electromagnetic interference it sends out to ensure that the electromagnetic environment is qualified. Secondly, the immunity of electromagnetic interference. This means that the product should be able to operate normally in an electromagnetic environment with specified electromagnetic interference intensity without reducing its performance indicators. Thirdly, the standardization and compatibility of the electromagnetic environment. Any measures taken against electromagnetic interference cannot degrade the performance of itself or other products or systems in the same electromagnetic environment, and can only coexist in a friendly and peaceful manner. For example, in order to reduce conducted interference, capacitors are connected in parallel between the phase line and ground line of the equipment power supply. For the equipment, the capacity of the capacitor must meet the limit value requirements for leakage current in the * * standard; For the system, it is necessary to prevent it from becoming a coupling source of system interference and affecting its operation. Therefore, EMC testing of products should include two main aspects:
(1) Test the electromagnetic interference intensity it sends to the outside world to confirm whether it meets the limit value requirements specified in relevant standards;
2) Conduct sensitivity testing on it under electromagnetic environmental conditions with specified electromagnetic disturbance intensity to confirm whether it meets the immunity requirements specified in relevant standards.
