LED lights in the fourth quarter of 2015 quality inspection results released: electromagnetic compatibility is not up to standard
In this spot check, more than half of the unqualified products did not meet the standards for electromagnetic compatibility performance indicators such as power terminal disturbance voltage and radiated electromagnetic disturbance. It is worth noting that this phenomenon is not only prominent in this spot check. In fact, in the previous quality inspections, the problem of non-compliance with electromagnetic compatibility is also very serious. So what exactly are these non-compliant electromagnetic compatibility projects? What are the hazards and effects? How can we overcome these problems? How to detect this?
The power terminal disturbance voltage and radiation disturbance are not unfamiliar in our daily life. For example, turning on the hair dryer may cause interference to the normal playback of the TV screen next to it. This is the power terminal disturbance voltage, which is passed. The power cord harasses other electrical equipment in the same power grid. Another example, when a mobile phone calls, it may cause the computer screen that is being used to flash. This is radiation harassment, which is used to radiate the field strength through space. No matter what kind of medium is used to spread electromagnetic disturbance, when the disturbance reaches a certain level, it will cause interference to other electrical equipment in the same power grid or environment, thus affecting the normal operation and operation of other electrical equipment, and serious possibility to the power grid. The safe operation and human health have adverse effects.
The power terminal disturbance voltage and radiation disturbance test items are not only one of the 3C “Compulsory Product Certification System†projects of China's related products, but also one of the mandatory indicators of EU CE certification. That is to say, if you want to enter the Chinese market or related products in Europe and other markets, you must meet the requirements of the corresponding electromagnetic compatibility indicators.
The improvement of the above electromagnetic compatibility index is not difficult, and the large-scale unqualified one is mainly because the enterprise does not pay enough attention. In fact, with the development of dimming control systems, LED lights have become more and more intelligent, but the problem of electromagnetic disturbance is also increasing. To solve the electromagnetic disturbance problem, it is necessary to carry out professional tests, and analyze and judge the interference source and its characteristics, interference channels, etc., and take corresponding measures. Common measures to improve the electromagnetic disturbance capability of LED lighting products, such as change/optimization filtering Circuit, common mode / differential mode capacitor, etc. The test can be carried out in accordance with the national mandatory standard "GB 17743 Limits and Measurement Methods for Radio Disturbance Characteristics of Electrical Lighting and Similar Equipment". The power terminal disturbance voltage test system is mainly composed of an EMI test receiver, a manual power network (LISN) and EMC test software.
Power terminal disturbance voltage test diagram
The test of radiated disturbance is relatively complicated. The corresponding test system and conditions are different for different radiation frequencies. The following figure is the radiation disturbance test system of LED light with low frequency magnetic field (test frequency 9kHz~30MHz), mainly by three Loop antenna, EMI receiver, EMC test software and other components.
Schematic diagram of three-ring radiation test layout
Due to the increasing severity of electromagnetic pollution, in order to avoid the impact on the test results of the above test items, the above electromagnetic compatibility test can generally be carried out in an electromagnetic shielding room or an anechoic chamber. By installing a radio frequency absorbing material on the surface of the shielding room, or using a metal plate (net) to absorb the incident electromagnetic wave, the interface reflection loss and the reflection loss inside the plate, to avoid external electromagnetic interference entering the room, affecting the measurement results.
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