The Main Electromagnetic Disturbance Source of Electronic and Electrical Products

According to the characteristics of each project, we can divide all the testing projects into three categories and discuss them respectively. They are: electromagnetic disturbance emission category (There are conduction emission and radiation emission.), Harmonic current category, and Transient pulse immunity category (there are electrostatic discharge, electric rapid pulse, surge impact)

Countermeasures and corrective actions of common problems from electromagnetic disturbance emission test. As for the countermeasures and rectification of electromagnetic emission test, we will discuss it in detail on next topic, taking the example of AV and IT products, the topic is the common EMC problems and the countermeasures in the process of electronic products 3 C authentication test, we only make an outline introduction here, and won’t make further discussion.

The leading electromagnetic disturbance source of electronic, electrical products

The switch circuit of equipment switching power supply: the main frequency of disturbance source is dozens of kHz to hundreds of KHz, for high harmonic, it may extend to dozens of MHz. The rectifier circuit of Dc power supply: The frequency limit of rectifier noise frequency power may be extended to hundreds of kHz; the frequency limit of high frequency rectifier noise can be extended to dozens of MHz. The brush noise of electric equipment dc motor: Noise frequency limit can be extended to several hundred MHz. The running noises of electric equipment dc motor: High harmonic may be extended to dozens of MHz.

Harassment emission of variable-frequency control circuit: Disturbance source frequency is from dozens of kHz to dozens of MHz.
The switch noise when the device is under running: the noise frequency limit can be extended to hundreds of MHz.

The device’s crystal oscillator of intelligent control and electromagnetic disturbance of digital circuit: basic frequency of disturbance source is from dozens of KHz to dozens of MHz, high harmonic can be extended to hundreds of MHz.

Microwave leakage of Microwave devices: basic frequency of disturbance source is GHz.

The electro-magnetic interference of electromagnetic induction heating equipment: basic frequency of disturbance source is dozens of kHz; high harmonic can be extended to hundreds of MHz.

The vibration and its harmonic of high frequency tuning circuit of TV electro acoustic receiving equipment: basic frequency of disturbance source is from dozens of MHz to MHz, high harmonic can be extended to several GHz.

The digital processing circuit of the Information technology equipment and all kinds of automatic control equipments: basic frequency of disturbance source is dozens of MHz to hundreds of MHz; high harmonic can be extended to several GHz.

Tags：EMC Disturbance , EMC Source