What problems will arise from EMC's rectification and what are the solutions?

Published on.

2022-05-27 17:17

EMC (electromagnetic compatibility) refers to the ability of equipment or system to operate as required in its electromagnetic environment without causing intolerable electromagnetic interference to any equipment in its environment. EMC rectification testing covers a wide range of fields, but no matter what industry, there will be some failures when doing EMC rectification testing. This is also something that every industry needs to consider and avoid. What are the common problems in EMC rectification testing? Let's have a look.


1、 Radio frequency noise on the cable. The method of debugging is usually to separate as many I/O cables as possible, if the manufacturer encounters radiation problems in the test laboratory. You can start reconnecting the cables one-to-one until the radiation disappears. If there are multiple cables, each cable may cause specific problems, and connecting/disconnecting them in various configurations may lead to seemingly inconsistent measurement results, which is usually due to the connection/disconnection of grounding loops of different sizes. The rule of thumb to remember in the design phase is to make the RF energy of each cable as small as possible, to ensure that as little as possible unintentional noise is coupled to the external and internal cables, and to avoid radiation problems caused by cables.
2、 Connector grounding ESD problem. Determine the ESD test location. Unless otherwise specified in relevant product or product series standards, electrostatic discharge is only applicable to the points and surfaces that people can contact during normal use of EUT. In order to see if they can find any vulnerable location, the testing laboratory will conduct some exploratory tests on the product shell. If the chassis is not conductive, there are usually not many discharge points. Even on the non-conductive chassis, there are some common discharge points: buttons/keyboards; Screw head; Connector; The area near the chassis inside the PCB; The connection between two parts of the chassis. At 8kV or 16kV, the arc distance may be very long, so the discharge may find a path to the circuit board, even through the non-conductive enclosure.
3、 Solution to conduction problem: 1. Reduce EMI current through series high impedance. 2. Short circuit the EMI current to ground or direct it to another loop conductor by paralleling a low impedance. 3. Cut off EMI current through current isolation device. 4. Control EMI current through self action.
4、 EMC solution for inductance and series loss. When the capacitor is connected in series in the power supply or signal circuit, the following requirements shall be met: 1. The working current flowing through the capacitor shall not cause overheating or excessive inductance, which is worse than this; 2. The flowing current will not cause inductance saturation, especially for high permeability materials. The solution is: magnetic core material, ferrite and ferrite loaded cable; Inductance, differential mode and common mode; Grounding choke; Inductive capacitor combination element.
The above is an introduction to some common problems and solutions in EMC rectification. To avoid problems in EMC rectification, you must master EMC's knowledge and skills and be familiar with the causes of each problem, so that you can better conduct EMC rectification tests.


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