The use of ferrite magnetic ring in anti-EMI, the development of ferrite magnetic ring is with the rapid development of modern electronic equipment and communication equipment, and the subsequent electromagnetic interference affects the normal operation of other nearby electronic equipment The problem has attracted worldwide attention.

Domestic and foreign countries have successively adopted a series of measures in anti-electromagnetic interference, and have formulated electromagnetic radiation environmental protection laws and mandatory standards for electromagnetic compatibility for power equipment, automobiles, radio receivers, home appliances, office equipment, and information technology equipment. .

Among the many anti-electromagnetic interference measures, the EMI power filter is a very effective device. It is a passive low-pass network composed of passive components that can attenuate common mode EMI signals and differential mode EMI signals at the same time. Among them, common mode choke coils that mainly suppress common mode interference signals mostly use ferrite magnetic rings as cores, because in most cases all components are assembled in shielded metal or unshielded plastic shells. A self-hardening, flame-retardant thermoplastic synthetic resin is used as the potting material. Therefore, in addition to high magnetic permeability and good high-frequency characteristics, the inductance of the ferrite ring is also required to be in the thermoplastic potting material. There should be no significant reduction after sealing. To this end, we sampled two domestically produced ferrite magnetic rings for corresponding tests.