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Do not understand electromagnetic interference? Reading EMI from Common Mode Electromagnetic Interference Examples
Apr 27, 2017

Do not understand electromagnetic interference? Reading EMI from Common Mode Electromagnetic Interference Examples

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Electromagnetic interference, also known as EMI (Electromagnetic Interference). The modern society we live in is in a variety of electronic device environments. The electromagnetic signals radiated from these electronic devices affect each other, which is called electromagnetic interference (EMI). Do not understand electromagnetic interference? It does not matter, we will understand electromagnetic interference through this example of common mode electromagnetic interference.


Electromagnetic interference is commonly found in electromagnetic signal devices and large energy devices. The electromagnetic signals generated by these devices will interfere with the normal operation of the device itself, and may also affect the surrounding electronic devices. We will use electromagnetic interference examples to illustrate.


For example, the ignition of the engine of some steam locomotives causes interference to the television and appears on the television screen in a striped manner, or causes interference with the radio and appears on the speaker in the form of scrambled beans or background noise. While listening to the sound may be lifted or high frequency The noise generated by the equipment is transmitted to the audio equipment to cause unpleasant sound output, or it may be caused by the start of the refrigerator when the home computer is used, causing a malfunction of the computer and the like. These are the most intuitive manifestations of electromagnetic interference.


Common-mode electromagnetic interference is one of many electromagnetic interferences. Common-mode inductors exist to eliminate common-mode electromagnetic interference and there are special inductors.


Taking a normal switching power supply as an example, the operating frequency is above 20KHZ, and the electromagnetic interference generated by it is higher than 20KHZ, generally between 150KHZ and 30MHZ. For this band, the common mode interference exceeds the standard, and one can choose to increase the maximum in harmful frequencies. Impedance of the common-mode inductance to suppress, how to improve the impedance has become the focus of the developers need to solve, use the smaller the distributed capacitance of the inductor, the higher the high-frequency impedance, the better the principle of EMI, the gain UU common-mode inductor is greatly improved The impedance performance of the inductor plays a good role in conducting common-mode interference. Through tests, it has been found that the Z value of the highest point of the product or the specified frequency range of the product Z is found, thereby judging the condition affecting EMI and finally obtaining the frequency from the EMI abnormality. Increasing the Z-value and reducing the distributed capacitance can effectively suppress EMI.


The inductors used by Gain Industries to eliminate common-mode EMI are divided into four major categories: UU-type common-mode inductors (representing products: UU9.8, UU10.5) and EE-type common-mode inductors (representing EE8.3). , UC type common mode inductors, and ring common mode inductors. It can effectively suppress EMI and achieve good elimination of common mode electromagnetic interference.


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