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Introduction to electromagnetic compatibility testing technology

Issue Time:2019-05-15
Overview
The electromagnetic compatibility test tests the equipment according to the methods specified in the relevant electromagnetic compatibility standards to assess whether it meets the standard requirements. EMC performance must meet standard requirements before finalizing and entering the market.

EMC test project
EMC measurements fall into two main categories: Electromagnetic Interference (EMI) and Electromagnetic Susceptibility (EMS).

Electromagnetic emission
1. Radiated Emission (Radiated Emission)

Test electromagnetic energy propagating through space.

2. Conducted Emission (CE)

Test electromagnetic energy propagating along a power line, control line, or signal line.

Immunity EMS
1. Radiation Susceptibility (RS):

Test the immunity of the equipment under test to electromagnetic interference in space.

2. Power frequency magnetic field sensitivity test PMS (Power frequency magnetic susceptibility)

Verify the immunity of electrical and electronic products to power frequency magnetic fields.

3. Conducted susceptibility of RF field induction (Conducted susceptibility)

Test the sensitivity of the device under test to electromagnetic energy transmitted along a power line, control line, or signal line.

4. Electrical fast transient burst immunity EFT / B (Electrical fast transient burst)

Analog switching to inductive loads (eg relays, contactors); interference to high voltage switch switching (eg vacuum switches, sulphur hexafluoride) equipment. The discharge waveform is a pulse train of 5 ns/50 ns (rising edge 5 ns, half-wave time 50 ns) with a burst duration of 15 ms and a pulse period of 300 ms. It is characterized by fast rise time, short duration, low energy, but high repetition rate.

5. Surge immunity SURGE

Simulate faults in the grid; lightning strikes (directly or indirectly) to equipment, and switching operations in the grid. The discharge waveform is a pulse with an open circuit voltage of 1.2us/50us and a short circuit current of 8us/20us. It is characterized by slow rise time (relative to EFT/B), long duration and high energy.

6. Voltage drop and interrupt immunity DIP/interruption

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

7. Power line induction / contact (Power induction / contact)

The analog outdoor signal line is too close to the power line or has a contact failure.

8. Electrostatic discharge immunity ESD (Electrostatic discharge)

Simulate the discharge of an operator or object as it contacts the device and the discharge of a person or object to an adjacent object.

Evaluation of EMC test results

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

Class A: Performance indicators in the test are normal;

Grade B: The performance is temporarily reduced during the test, the function is not lost, and it can be recovered after the test;

Class C: The function is allowed to be lost, but it can be self-healing, or it can be recovered after operator intervention;

Class R: Loss of function or performance that cannot be recovered due to equipment (components) or software damage or data loss, except for protective components.

The importance of product EMC design
The EMC design of the product guarantees the EMC performance of the product, and the EMC performance of the product directly relates to the market access of the electronic product. With the extensive use of electronic equipment, countries feel the importance of EMC performance of the product. The regulations require EMC requirements for electronic products entering the domestic market, such as:

The European Community--89/336/EEC DIRECTIVE------ expressly requires that the product must comply with the requirements of the relevant EMC standards of the European Community, otherwise it shall not be sold in the European Community market. Offenders will be subject to penalties for penalties and market bans.

The United States requires communications products entering the country to comply with FCC PART 15 and 68 requirements;

South Korea requires communications products to comply with EMC requirements, otherwise no network access will be issued.

China's home appliances have enforced EMC standards; communication power products have begun to implement EMC standards in October 2001, and some of the company's product development has been affected by this, and the progress has been postponed.

In addition, the EMC performance of the product is also related to the stability of the product and affects customer satisfaction; the main performance is:

Product EMC design considerations cause internal crosstalk and affect product stability;

Poor resistance to external interference, difficult to work;

Interference can cause customer complaints.

The EMC performance of the final product is also closely related to the competitiveness of the product. Whether the same product has not passed CE certification can often play a decisive role in market competition.

Therefore, in order to participate in international competition and become an internationalized large company, we must carry out EMC design of products and solve EMC problems of products.

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