Three important rules about EMC certification

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Three important rules about EMC certification　 [Copy link]

1) Rule 1, EMC cost-effectiveness ratio rule: The earlier EMC issues are considered and resolved, the lower the cost and the better the effect. Carrying out EMC design in the new product development stage can greatly save costs and improve efficiency, rather than waiting until the product fails the EMC test. On the contrary, the efficiency will be greatly reduced and the cost will be greatly increased. Experience tells us that it is the most time-saving and economical to carry out EMC design at the same time as functional design, and pass the EMC test when the sample and prototype are completed. On the contrary, if EMC is not considered in the product development stage, and improvements are not made until EMC is found to be unqualified after production, it will not only bring great technical difficulties, but also rework will inevitably bring great waste of costs and time. It may even be impossible to implement improvement measures due to defects in structural design and PCB design, resulting in the product not being able to be launched on the market. 2) Rule 2, the larger the high-frequency current loop area S,The more serious the EMI radiation. The high-frequency signal current flows through the path with the least inductance. When the frequency is high, the general routing reactance is greater than the resistance, and the connection is an inductor for the high-frequency signal, and the series inductor causes radiation. Most of the electromagnetic radiation is generated by the high-frequency current loop on the EUT device under test. The worst case is the open-circuit antenna form. The corresponding treatment method is to reduce and shorten the connection, reduce the area of the high-frequency current loop, and try to eliminate any antenna required for abnormal normal operation, such as discontinuous wiring or too long pins of components with antenna effect. One of the most important tasks to reduce radiated interference or improve the anti-interference ability of RF radiation is to find ways to reduce the high-frequency current loop area S. 3) Rule three, the higher the loop current frequency f, the more serious the EMI radiation caused, and the electromagnetic radiation field strength increases in direct proportion to the square of the current frequency f. The second most important way to reduce radiated interference or improve the anti-interference ability of RF radiation is to find ways to reduce the high-frequency current frequency f of the interference source, that is, to reduce the frequency of the harassing electromagnetic wave. National Standard for EMC Technology National standard for electromagnetic compatibility technology, also known as (national standard for electromagnetic compatibility, national standard for EMC) Basic standards GB/T 4365--1995 Electromagnetic compatibility terminology GB/T 6113--1995 Specification for radio interference and immunity measuring equipment GB 3907--83* Basic measurement methods for industrial radio interference GB 4859--84* Basic measurement methods for the immunity of electrical equipment GB/T 15658--1995 General standard for urban radio noise measurement methods GB 8702--88 Regulations on electromagnetic radiation protection GB/T 13926.1--92 General theory on electromagnetic compatibility of industrial process measurement and control equipment GB/T 13926.2--92 Electrostatic discharge requirements for electromagnetic compatibility of industrial process measurement and control equipment GB/T 13926.3--92 Requirements for radiated electromagnetic fields of electromagnetic compatibility of industrial process measurement and control equipment GB/T 13926.4--92 Electromagnetic compatibility of industrial process measurement and control equipment - Requirements for electrical fast transients and bursts GB/T 14431--93 Signal/interference protection ratio and minimum usable field strength required for radio services Product category (product family) GB 4343--1995 Measurement methods and allowable values of radio interference characteristics of household and similar electric and heating appliances, electric tools and similar electrical appliances GB 4824--1996 Measurement methods and limits of electromagnetic disturbance characteristics of industrial, scientific and medical (ISM) radio frequency equipment GB 6833.1--86* General rules for test specifications for electromagnetic compatibility of electronic measuring instruments GB 6833.2--87* Test specifications for electromagnetic compatibility of electronic measuring instruments - Magnetic field sensitivity test GB 6833.3--87* Test specifications for electromagnetic compatibility of electronic measuring instruments - Electrostatic discharge sensitivity test GB 6833.4--87* Test specifications for electromagnetic compatibility of electronic measuring instruments - Power supply transient sensitivity test GB 6833.5--87* Test specifications for electromagnetic compatibility of electronic measuring instruments - Radiated sensitivity test GB 6833.6--87* Test specification for electromagnetic compatibility of electronic measuring instruments - Conducted susceptibility test GB 6833.7--87* Test specification for electromagnetic compatibility of electronic measuring instruments - Non-operating magnetic field interference test GB 6833.8--87* Test specification for electromagnetic compatibility of electronic measuring instruments - Operating magnetic field interference test GB 6833.9--87* Test specification for electromagnetic compatibility of electronic measuring instruments - Conducted interference test GB 6833.10--87* Test specification for electromagnetic compatibility of electronic measuring instruments - Radiated interference test GB 7343--87* 10kHZ～30MHZ Passive radio interference filter and suppression element - Measurement method for suppression characteristics GB 7349--87* High-voltage overhead transmission line, substation radio interference measurement method GB 9254--88 Limits and measurement methods for radio interference of information technology equipment GB 9383--1995 Limits and measurement methods for conducted immunity of sound and television broadcast receivers and related equipment GB 13421--92 Limits and measurement methods for spurious emission power levels of radio transmitters GB 13836--92* Allowable values and measurement methods for radiated disturbance characteristics of equipment and components of cable distribution systems for 30MH2~1GH sound and television signals GB 13837--1997 Limits and measurement methods for radio disturbance characteristics of sound and television broadcast receivers and related equipment GB/T 13838--92 Allowable values and measurement methods for radiated immunity characteristics of sound and television broadcast receivers and related equipment GB 13839--92 Allowable values and measurement methods for internal immunity of sound and television broadcast receivers and related equipment GB 14023--92 Measurement methods and allowable values for radio disturbance characteristics of vehicles, motor vessels and devices driven by spark ignition engines GB 15540--1995 Technical requirements and measurement methods for electromagnetic compatibility of land mobile communication equipment GB 15707--1995 Limits of radio interference from high-voltage AC overhead power transmission GB/T15708--1995 Methods of measurement of radio radiation interference generated by operation of electric locomotives on AC electrified railways GB/T15709--1995 Methods of measurement of radio radiation interference from contact lines on AC electrified railways GB 15734--1995 Limits and measurement methods of radio disturbance characteristics of electronic dimming equipment GB 15949--1995 Limits and measurement methods of immunity characteristics of equipment and components of cable distribution systems for sound and television signals GB/T 16607--1996 Methods of measurement of radiated interference from microwave ovens above 1 GHz B 16787--1997 G 30MHz~1GHz sound and television signal cable distribution system radiation measurement methods and limits GB 16788--1997 30MHz~1GHz sound and television signal cable distribution system immunity measurement methods and limits system class GB 6364--86 Electromagnetic environment requirements for aeronautical radio navigation stations GB 6830--86 Allowable value of telecommunication lines subjected to dangerous influences of strong electric lines GB 7432--87* Index of coaxial cable carrier communication system against radio broadcasting and communication interference GB 7433--87* Index of symmetrical cable carrier communication system against radio broadcasting and communication interference GB 7434--87* Index of overhead open wire carrier communication system against radio broadcasting and communication interference GB 7495--87 Protection distance between overhead power lines and AM radio stations GB 13613--92 Electromagnetic environment requirements for long-distance radio navigation stations in the sea GB 13614--92 Electromagnetic environment requirements for short-wave radio direction-finding stations (stations) GB 13615--92 Electromagnetic environment protection requirements for earth stations GB 13616--92 Electromagnetic environment protection requirements for microwave relay stations GB 13617--92 Electromagnetic environment requirements for short-wave radio receiving stations (stations) GB 13618--92 Requirements for electromagnetic environment protection of air intelligence radar stations GB/T13620--92 Determination of coordination area and interference calculation method between satellite communication earth station and ground microwave station EMC standards adopted for EMC certification of household electrical appliances At present, there are three EMC standards adopted for EMC certification of household electrical appliances: GB 4343-1995 "Measurement methods and allowable values of radio interference characteristics of household and similar electric and electric heating appliances, electric tools and similar electrical appliances" This standard was issued on August 25, 1995 and implemented on December 1, 1996. GB4343.2-1999 "Requirements for electromagnetic compatibility of household appliances, electric tools and similar appliances Part 2 Immunity" This standard was issued on March 23, 1999 and implemented on April 1, 2000. GB 17625.1-1998 "Limits of harmonic currents emitted by low-voltage electrical and electronic equipment (equipment with current of ￡16A per phase)" This standard was issued on December 14, 1998 and implemented on December 1, 1999. At present, this standard is encouraged to be adopted. If it fails to meet the standards, it will not be used as the basis for the overall judgment of the certification. Inspection items for EMC certification of household electrical appliances The EMC inspection items for EMC certification of household electrical appliances include two aspects: electromagnetic emission (EMI) and electromagnetic immunity (EMS): (I) Inspection items for electromagnetic emission (EMI) are: ①. Continuous interference voltage (150kHz～30MHz); ②. Intermittent interference voltage (click) (150kHz, 500kHz, 1.4 MHz and 30MHz); ③. Interference power (30MHz～300MHz) ④. Harmonic current (2nd to 40th harmonic) (II) Electromagnetic immunity (EMS) test items are: ①. Electrostatic discharge immunity; ②. Radiated electromagnetic field (80MHz to 1000 MHz) immunity; ③. Electrical fast transient/burst immunity; ④. Surge (lightning) immunity; ⑤. Injection current (150kHz to 230MHz) immunity; ⑥. Voltage sag and short interruption immunity. Key components for EMC certification of household appliances. The main EMC key components of household appliances included in the first batch of catalogs are as follows: 1. Air conditioner: compressor, computer control board (including inverter), negative ion generator, power filter 2. Refrigerator, refrigerator-freezer, freezer: compressor, computer control board (including inverter), power filter, mechanical thermostat 3. Washing machine: program controller (including timer), computer control board, power filter, motor 4. Rice cooker: thermostat, computer control board, electric hot plate 5. Electric iron: electric heating tube, thermostat 6. Electric fan: computer control board, motor 7. Hair dryer: motor, filter, speed regulator Three major rules Rule 1: EMC cost-effectiveness relationship rule: The earlier the EMC problem is considered and solved, the lower the cost and the better the effect. EMC design in the new product development stage can greatly save costs and improve efficiency compared to waiting until the product EMC test fails to pass the improvement; on the contrary, the efficiency will be greatly reduced and the cost will be greatly increased. Experience tells us that it is the most time-saving and economical to carry out EMC design at the same time as functional design and pass EMC test when the sample and prototype are completed. On the contrary, if EMC is not considered in the product development stage and improvements are made only after EMC is found to be unqualified after production, it will not only bring great technical difficulties, but also rework will inevitably bring great waste of costs and time. Even due to defects in structural design and PCB design, improvement measures cannot be implemented, resulting in the product not being able to be launched on the market. Rule 2: The larger the high-frequency current loop area S, the more serious the EMI radiation. High-frequency signal current flows through the path with the minimum inductance. When the frequency is high, the wiring reactance is generally greater than the resistance, and the connection is an inductor for high-frequency signals, and the series inductor causes radiation. Most electromagnetic radiation is generated by the high-frequency current loop on the EUT device under test, and the worst case is the open-circuit antenna form. The corresponding treatment method is to reduce and shorten the connection, reduce the area of the high-frequency current loop, and try to eliminate any antennas required for abnormal operation, such as discontinuous wiring or excessively long pins of components with antenna effect. One of the most important tasks to reduce radiated interference or improve the ability to resist RF radiation interference is to find ways to reduce the high-frequency current loop area S. Rule 3: The higher the loop current frequency f, the more serious the EMI radiation caused, and the electromagnetic radiation field strength increases in direct proportion to the square of the current frequency f. The second most important way to reduce radiated interference or improve the ability to resist RF radiation interference is to find ways to reduce the high-frequency current frequency f of the interference source, that is, to reduce the frequency f of the harassing electromagnetic wave.