EMC (Electromagnetic Compatibility Testing) is the full name of Electro Magnetic Compatibility, which is defined as "the ability of equipment and system to work normally in its electromagnetic environment and not to cause unbearable electromagnetic disturbance to anything in the environment". This definition contains two meanings. First, the equipment should work normally in a certain electromagnetic environment, that is, the equipment should have one. Fixed electromagnetic immunity (EMS); secondly, the electromagnetic disturbance generated by the equipment itself can not have too great impact on other electronic products, namely electromagnetic disturbance (EMI). The test items of EMI are: harmonic current (2-40 harmonics), flicker Flicker (CE), radiation disturbance (RE) EMS (1). ESD (Electrostatic Discharge Immunity); 2. Radiated electromagnetic field (80MHz-1000MHz) immunity (RS); 3. Electric fast transient/pulse group immunity; 4. Surge (lightning strike) immunity; 5. Injection current (150kHz-230MHz). (CS); _. Voltage sag and short-term interruption immunity 1. Harmonic (harmonic test) Standard: EN61000-3-2a stipulates the limits of harmonic currents transmitted to public power grids. B) specify the limits of the harmonic components of the input current generated by the device under test in a particular environment. C) Applicable to electronic and electrical equipment with input current less than or equal to 16A connected to public low voltage network. Harmonic testing mainly examines the possible impact of harmonics in low-voltage power supply networks on these frequency-sensitive devices. Harmonic experiment principle: Because of the working mode of electronic equipment, non-linear components and various interference noises, the input current of electronic equipment is not completely positive flashing wave, which often contains abundant high-order harmonic components to pollute the power grid. Harmonics in power systems refer to sinusoidal voltages or currents whose frequencies are integral times the rated frequencies of the power supply system. Harmonic currents in public transmission systems can cause the following problems: 1. Loss of more electric energy, each harmonic has reactive power and active power parts (active power will heat the conductor, leading to larger conductor area); 2. Shortening the service life of electronic components; 3. Reducing the harmonic voltage caused by voltage distortion is caused by superimposed on the power supply voltage. One or more combined waves of continuous positive flare waves are formed. Harmonics lead to voltage distortion in power grid 2. Voltage fluctuation and flicker Flicker Standard: EN 61000-3-3a) limits on the impact of constant voltage fluctuation and flicker on public power grid. B) Specify the limits of voltage variation produced by the tested prototype under specific conditions and the guidance of evaluation methods. C) 220 V to 250V for access to public low-voltage networks with input current less than or equal to 16A per phase. The purpose of this standard is to ensure that the product does not cause excessive flicker effects (light flicker) on lighting devices connected to it. The following table shows the allowable minute rate or time of change for each relative voltage change value. It can be understood that the larger the range of voltage change, the smaller the allowable speed of change, or the longer the time required to change. 3. Conducted Harassment CE (0.15-30 MHz) Standard: EN61000-6-4 A), Electronic and Electrical Measurement and Testing Equipment B, Electronic and Electrical Control Equipment C) Classification of Equipment Class A: Equipment suitable for use in all establishments other than domestic and directly connected to a low voltage supply network which supplies in. Class B: (Household) equipment suitable for use in domestic establishments and in establishments directly connected to a low voltage power supply network which supplies buildings for domestic purposes. For the wavelength of this kind of electromagnetic wave, the spare cable has less than one wave (30MHz is 10m), and the radiation efficiency to the air is very low. So if the noise voltage induced on the cable can be measured, the electromagnetic noise interference level in this frequency band can be measured. This kind of noise is conduction noise. The function of LISN: 1. It acts as high frequency isolation between EUT and power supply, avoiding noise from power supply entering EUT and affecting measurement results. 2. Simulate the actual power supply impedance to provide the specified impedance between the power terminals of EUT, so as to unify the measurement results. 3. Maintain the impedance stability of 50 Euros in the test frequency band to match the input impedance of the measurement receiver/spectrum analyzer. 4. Radiation harassment RE (30-1000MHz) Standard: EN61000-6-4 Classification of equipment Class A: equipment suitable for use in all establishments other than domestic and those directly connected to a low voltage power supply network which supplies buildings for domestic purposes. And in establishments directly connected to a low voltage power supply network which supplies buildings for domestic purposes. household a) electronic and electrical measurement and testing equipment b) electronic and electrical control equipment c) experimental principle of radiation disturbance of electronic and electrical laboratory equipment: the total length of the antenna is greater than 1/20 of the signal wavelength lambda, which will produce effective radiation to space When the length of the antenna is an integer multiple of lambda/2, the radiation energy is the largest. When the noise frequency is greater than 30MHz, the cable, opening and gap of electronic equipment can easily meet the above conditions, forming radiation emission.