What is EMC? What are the common EMC test items?

Date：2022-08-18 15:43:00Views：942

Electromagnetic compatibility (EMC) refers to the ability of equipment or system to operate in accordance with the requirements in its electromagnetic environment without generating unbearable electromagnetic interference to any equipment in its environment. Therefore, EMC includes two requirements: one is that the electromagnetic interference generated by the equipment to the environment during normal operation cannot exceed a certain limit; On the other hand, it means that the appliance has a certain degree of immunity to the electromagnetic interference existing in the environment, that is, electromagnetic sensitivity.

Various operating power equipment are related to each other and affect each other in three ways: electromagnetic conduction, electromagnetic induction and electromagnetic radiation. Under certain conditions, it will cause interference, influence and harm to the operating equipment and personnel. Interference is divided into internal interference and external interference.

Internal interference refers to the mutual interference between various components in the electronic equipment, including the following:

(1) Interference caused by leakage of working power through distributed capacitance and insulation resistance of the line; (related to working frequency)

(2) Interference caused by mutual coupling of signals through the impedance of ground wire, power supply and transmission conductor, or mutual inductance between conductors;

(3) Interference caused by heating of some elements in the equipment or system, which affects the stability of the element itself or other elements;

(4) The magnetic field and electric field generated by high-power and high-voltage components affect the interference caused by other components through coupling.

External interference refers to the interference of factors other than electronic equipment or system to the line, equipment or system, including the following:

(1) External high voltage and power supply interfere with electronic circuit, equipment or system through insulation leakage;

(2) External high-power equipment generates a strong magnetic field in space and interferes with electronic circuits, equipment or systems through mutual inductance coupling;

(3) Interference of space electromagnetic wave on electronic circuit or system;

(4) Unstable working environment temperature, causing interference caused by changes in parameters of electronic circuits, equipment or internal components of the system;

(5) Equipment powered by industrial power grid and interference caused by grid voltage passing through power transformer.

Inspection items of EMI:

1. Conduction (CE) (150kHz ～ 30MHz);

2. Intermittent interference voltage (click) (150kHz, 500KHz, 1.4 MHz and 30MHz);

3. Interference power (30MHz ～ 300MHz);

4. Harmonic current (2 ~ 40th harmonic);

5. Blink flicker.

Inspection items of EMS:

1. Electrostatic discharge immunity;

2. Immunity of radiated electromagnetic field (80MHz ~ 1000MHz);

3. Electrical fast transient / burst immunity;

4. Surge (lightning) immunity;

5. Immunity of injection current (150kHz ～ 230MHz);

6. Voltage sag and short-time interruption immunity.

Electromagnetic compatibility test items (EMC) common items and standards for conducted interference voltage EMC test:

Space radiation en55011,13,22 FCC art 15 & 18, VCCI

Conducted interference en55011,13,14-1,15,22, FCC art 15 & 18, VCCI

Click en55014-1

Power clamp en55013,14-1

Magnetic emission en55011,15

Low frequency immunity en50091-2

Electrostatic discharge (ESD) IEC61000-4-2, en61000-4-2, GB / t17626.2

Radiated Immunity (R / s): iec61000-4-3, en61000-4-3, GB / t17626.3

Burst immunity (EFT / b) iec61000-4-4, en61000-4-4, GB / t17626.4

Surge immunity (surge) iec61000-4-5, en61000-4-5, GB / t17626.5

Conducted disturbance immunity (C / s) iec61000-4-6, en61000-4-6, GB / t17626.6

Power frequency magnetic field immunity (M / s) iec61000-4-8, en61000-4-8, GB / t17626.8

Voltage drop (dips) iec61000-4-11, EN61000-4-11, GB / t17626.11

Harmonic current (iec61000-3-2, en61000-3-2)

Voltage flicker iec61000-3-3, en61000-3-3

There must be three factors for the system to have electromagnetic compatibility problems, namely, electromagnetic disturbance source, coupling path and sensitive equipment. Therefore, when encountering electromagnetic compatibility problems, we should start with these three factors, suit the remedy to the case, and eliminate one of them to solve the electromagnetic compatibility problems.