The working principle of the magnetic ring

The magnetic ring is composed of a magnetic core and a plastic shell or insulating varnish. The magnetic core is used to increase the magnetic induction intensity of the electromagnet, while the plastic shell or insulating varnish serves to protect the magnetic core, prevent moisture, and enhance insulation.

Magnetic rings can be mainly classified into ferrite magnetic rings, iron powder core magnetic rings, iron-silicon-aluminum magnetic rings, and amorphous magnetic rings according to the magnetic cores used.

I. Ferrite Imagnetic ring

Ferrite is a material produced by sintering a high-permeability magnetic material with one or more metals such as magnesium, zinc, and nickel at a high temperature of 2000℃. At low frequencies, the magnetic core exhibits very low inductive impedance, which does not affect the transmission of useful signals on data or signal lines. However, at high frequencies, starting from around 10MHz, the impedance increases. The inductive component remains small, but the resistive component rapidly increases, forming a low-pass filter.

Ferrite magnetic rings primarily consist of nickel-zinc ferrite and manganese-zinc ferrite magnetic rings, which are further categorized into low permeability rings and high permeability rings based on their magnetic permeability.

The permeability of manganese-zinc ferrite magnetic ring material is generally above 1000, making it known as a high-permeability magnetic ring. Manganese-zinc ferrite magnetic rings, with their high permeability, are commonly used to wind common-mode inductors to suppress low-frequency common-mode conducted interference at power supply ports.

Nickel-zinc ferrite, with a permeability ranging from 100 to 1000, is known as a low-permeability ring. It is commonly used in various types of wires, such as power cords, HDMI cables, and USB cables.

II. Iron powder core magnetic ring

The iron powder core magnetic ring is composed of carbon-based iron magnetic powder and resin-coated carbon-based iron magnetic powder, and has a very low magnetic permeability. There is an air gap between the magnetic powder and the insulating material, with a general magnetic permeability ranging from 20 to 100. Due to the low magnetic permeability of the iron powder core magnetic ring, it is not easily saturated under high differential mode current conditions, making it commonly used to construct differential mode inductors. The iron powder core has a low filtering frequency band and is mainly used to suppress differential mode interference conducted through power lines.

III. Iron-silicon-aluminum magnetic ring

The iron-silicon-aluminum magnetic ring is one of the most commonly used magnetic rings. Iron-silicon-aluminum is composed of aluminum, silicon, and iron, and boasts a considerably high BMAX (the average maximum magnetic flux density across the crosssectional area of the magnetic core). Its magnetic core loss is significantly lower than that of iron powder cores. With high magnetic flux, low magnetic hysteresis (low noise), it serves as a low-cost energy storage material without thermal aging. It can be used as a substitute for iron powder cores and exhibits very stable performance at high temperatures.

The primary characteristics of iron-silicon-aluminum are lower loss compared to iron powder cores, excellent DC bias current characteristics, and a price range between iron powder cores and iron-nickel cores. Iron-silicon-aluminum magnetic powder cores exhibit superior magnetic properties, low power consumption, high magnetic flux density, and high reliability features such as high temperature resistance, moisture resistance, and vibration resistance.

With a wide range of magnetic permeability to choose from, it is the optimal choice for common mode inductors, PFC inductors, and resonant inductors in switching power supplies, offering a high cost-performance ratio.

IV. Amorphous magnetic ring

Amorphous magnetic ring is a magnetic ring-shaped structural device made of amorphous material, typically made of metal alloys with high magnetic permeability. This is a special type of material with unique magnetic and electrical properties. Compared to traditional crystalline magnetic materials, it has higher saturation magnetic induction intensity, lower hysteresis loss, and a wider frequency response range.

Based on the different materials used, amorphous magnetic rings can be categorized into iron-based amorphous, cobalt-based amorphous, etc. According to the shape of the material used, they can be divided into bulk-material-type magnetic rings and powder-type magnetic rings. Amorphous alloys, also known as metallic glasses, refer to a type of amorphous material with a special structure and complex composition consisting of multiple metals. In the manufacturing process of amorphous magnetic rings, powders of different metals are melted under vacuum, mixed in a uniform manner, and then rapidly cooled to form an amorphous alloy material. Finally, the amorphous alloy material is processed into magnetic rings or magnetic strips with specific shapes, lengths, widths, and other dimensions.

The housing of amorphous magnetic rings is usually made of plastic, which has a higher magnetic permeability compared to ferrite materials. Amorphous magnetic rings are commonly used to wind common-mode inductors to suppress low-frequency conducted common-mode interference.