Principle and design of EMC system integration_Century Wisdom (Suzhou) Testing Technology Co., Ltd

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Principle and design of EMC system integration

Release time:

2022-06-20 00:00

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　　EMC system integration refers to the ability of equipment or system to meet the requirements and work in its electromagnetic environment without causing unbearable electromagnetic interference to any equipment in the environment. Therefore, EMC has two requirements: one is that the electromagnetic interference to the environment in the normal operation of equipment does not exceed a certain limit; on the other hand, This means that there is a certain degree of anti-interference to electromagnetic interference in the environment where there is electromagnetic compatibility system integration, namely electromagnetic sensitivity, so let's understand the principle and design of electromagnetic compatibility system integration.

电磁兼容系统集成

　　Main research objects of EMC system integration:

　　Transmission line coronavirus noise, automobile noise, contactor itself noise, conductor discharge noise, electric locomotive noise, urban noise and other artificial noise; The interaction of various utility equipment (transmission lines, communications, railways, roads, oil and metal pipelines, etc.) within the shared corridor; Super high-rise towers and other large real estate reflection problems, electromagnetic environment, including strong wires and other power frequency field, medium, short wave, microwave electromagnetic radiation.

　　The impact of nuclear electromagnetic pulse, the electromagnetic pulse generated by high-altitude nuclear explosion can damage the ground command, control, communication, computer and newspaper systems, spectrum detection technology, its essence is aimed at the electromagnetic radiation and information leakage of information equipment, from the information receiving and protection of a series of studies.

　　In order to prevent the misoperation of electronic equipment, measures must be taken to improve the anti-interference of equipment, spectrum allocation and management, radio spectrum is a limited resource, but not expendable, must be managed scientifically, at the same time make full use of.

　　Measures to improve EMC system integration:

　　The use of a complete shield can prevent external radiation from entering the system and prevent the interference energy of the system from radiating to the outside. The integrity of the shield must be maintained and necessary doors, slits, vents and cable holes must be properly disposed of. The shield needs to be grounded reliably, the design of a reasonable grounding system, small signal, large signal interference circuit as far as possible separated grounding, grounding resistance as small as possible, the use of appropriate filtering technology, filter passband reasonable selection, the leakage loss will be reduced to a low place.

　　The use of limiting technology, limiting level is higher than the working level, and two-way limiting, accurate selection of connecting cables and wiring, when necessary, with optical cable instead of long cable, the use of balance differential circuit, shaping circuit, integral circuit and gate circuit technology, system frequency allocation if a system has multiple main frequency signals in the work, should try to avoid the frequency of the signals, Avoid each other's resonant frequency, share the corridor of all kinds of equipment, in the case of conditions, in order to reduce the impact of each other, should maintain a large interval.

　　The basic principle of integrated design of electromagnetic compatibility system:

　　Step 1 Ground

　　Grounding is an important issue in electronic equipment. The purpose of grounding is threescore. Grounding makes all the unit circuits of the entire circuit system have the common reference zero potential, so as to ensure the stable operation of the circuit system and prevent the interference of external electromagnetic field. Otherwise, the high voltage created by these charges may cause spark discharges inside the device, which can cause interference. In addition, as for the circuit shielding, if appropriate grounding is selected, good shielding effect can also be obtained. Work safely. When lightning induction occurs directly, damage to electronic equipment can be avoided; When the input voltage of commercial AC power supply is directly connected to the housing due to poor insulation or other reasons, it can avoid electric shock accidents for operators. In addition, since many medical devices are directly connected to the patient's body, 110V or 220V voltage on the shell will cause fatal danger, so grounding is the main method to suppress noise and prevent interference. Ground can be understood as an equipotential point or surface, which is the reference potential of a circuit or system, but not necessarily a geodetic potential. To ensure lightning damage and personnel safety, the shell of the electronic equipment and the metal parts of the equipment room must be connected to the ground. The ground resistance must be small to avoid exceeding the specified value.

　　Step 2: Screen

　　Shielding is the separation of metals between two regions of space to control the induction and radiation of electric, magnetic and electromagnetic fields from one region to another. Specifically, the element, circuit, component, cable or the noise source of the whole system is surrounded by a shield to prevent the external diffusion of the interfering electromagnetic field; Shielding a receiving circuit, device, or system from external electromagnetic fields.

　　The shield generates opposite electromagnetic field to absorb energy through electromagnetic induction in the shield layer, relative to external interference electromagnetic wave and internal electromagnetic wave from wires, cables, components, circuits or systems.

　　The selection principle of shielding material is as follows:

　　In the case of high frequency of interference electromagnetic field, the eddy current (P=I2R, low resistivity) generated in the metal material with low resistivity (high conductivity) consumes more power), forming a counteracting effect on external electromagnetic wave and obtaining shielding effect. In the case of low frequency interference electromagnetic wave, by using materials with high permeability, The magnetic force lines are enclosed inside the shield.

　　The above is the electromagnetic compatibility system integration principle and design, if you need to know more, please feel free to contact us!

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