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How to carry on the simple analysis of EMC electromagnetic compatibility knowledge, in view of this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

Basic knowledge of EMC

Electromagnetic compatibility EMC (Electromagnetic Compatibility)

The equipment can perform the coexistence of their respective functions together in the common electromagnetic environment, that is, the equipment will not be degraded due to the electromagnetic emission of other devices in the same electromagnetic environment; nor will it cause other devices in the same electromagnetic environment to cause unacceptable degradation due to their electromagnetic emission.

1. EMC test project

EMC measurement is mainly divided into two categories: electromagnetic interference EMI (Electromagnetic Interference) test and electromagnetic immunity EMS (Electromagnetic Susceptibility) test.

Electromagnetic emission

1.1. Radiation emission RE (Radiated Emission)

To test the electromagnetic energy transmitted through space.

1.2. Conducted emission CE (Conducted Emission)

Test the electromagnetic energy propagated along the power line, control line, or signal line.

Immunity EMS

2.1. Radiation sensitivity test RS (Radiated Susceptibility):

The immunity of the tested equipment to space electromagnetic disturbance was tested.

2.2. Power frequency magnetic field radiation sensitivity test PMS (Power frequency magnetic susceptibility)

Test the immunity of electronic and electrical products to power frequency magnetic field.

2.3. Conduction sensitivity CS (Conducted susceptibility) of radio frequency field induction

Test the sensitivity of the tested equipment to the electromagnetic energy transmitted along the power line, control line or signal line.

2.4. Electrical fast transient pulse group immunity EFT / B (Electrical fast transient burst)

Simulate the switching of inductive load (such as relays, contactors) and the interference to the switching equipment of high-voltage switches (such as vacuum switches, sulfur hexafluoride). The discharge waveform is a pulse train of 5ns/50ns (rising edge 5ns, half-wave time 50ns), the pulse duration is 15ms, and the pulse period is 300ms. It is characterized by fast rising time, short duration, low energy, but high repetition frequency.

2.5. Surge immunity SURGE

Simulation of faults in the power grid; interference of equipment by lightning (directly or indirectly), switching operation in the power grid. The discharge waveform is the pulse of open-circuit voltage 1.2us/50us and short-circuit current 8us/20us. It is characterized by slow rising time (relative to EFT/B), long duration and high energy.

2.6. Voltage drop and interrupt immunity DIP/interruption

Simulates instantaneous voltage drops and interruptions caused by faults in low-voltage, medium-voltage, or high-voltage networks (short-circuit or ground faults), as well as voltage changes caused by continuous changes in load connected to the grid.

2.7. Power line sensing / contact (Power induction/contact)

Simulate the close distance or contact fault between the outdoor signal line and the power line.

2.8. Electrostatic discharge immunity ESD (Electrostatic discharge)

Simulate the discharge of operators or objects when they come into contact with equipment and the discharge of people or objects to neighboring objects.

According to the standards established by our own scientific research achievements, such as GB/T15708 for the needs of world trade, many EMC standards in China have adopted CISPR and IEC standards. In fact, most countries in the world adopt the standards of CISPR and IEC.

II. Three elements of electromagnetic compatibility

Interference sources, interference pathways, sensitive equipment.

III. Propagation path of electromagnetic compatibility

EMI emission or damage caused by EMI is caused by the shell of the product, AC power terminal, DC power terminal, signal wire / control wire and ground wire.

Conducted interference: interference signals are transmitted through conductors (wires, inductors, capacitors). Appears in all kinds of conductors. Most of the frequency < 30mhz is this kind of interference.

two。 Radiation interference: the interference signal has been transmitted to the surrounding space in the form of electromagnetic field. It mainly appears in the media around the product. When the frequency is higher than 30mhz, the radiation becomes more obvious.

IV. Evaluation of EMC test results.

The EMI test results are based on whether a certain limit is met, and for EMS tests, the performance criteria can be divided into four levels:

Class A: the performance index is normal in the test.

Class B: the performance is temporarily reduced in the test, the function is not lost, and can recover itself after the test.

Level C: function is allowed to be lost, but can be restored by itself or after operator intervention.

Class R: with the exception of protective components, irrecoverable function loss or performance degradation caused by equipment (component) or software damage or data loss is not allowed.

5. Major international organizations of EMC standards

IEC- International Electrotechnical Commission

ITU- International Telecommunication Union

ANSI- American National Standards Institute

ETSI- European Telecommunication Standards Association

ASTM- American Society for Materials testing

IEEE- Association of Electrical and Electronic Engineers

CENELEC- European Electrotechnical Standardization Committee

This is the end of the answer to the simple analysis of EMC electromagnetic compatibility knowledge. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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