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Selection and application of magnetic rings

Based on the frequency band that needs to be suppressed, select the material of the magnetic ring; then, according to the thickness of the wire, choose the appropriate inner diameter size of the magnetic ring. Under the same material conditions, the length of the magnetic ring needs to be determined.

-- Selection of Magnetic Ring Material

The magnetic rings used for filtering cables are mainly made of manganese-zinc ferrite, nickel-zinc ferrite, and amorphous magnetic rings. The type of magnetic ring to be selected depends on the noise frequency: amorphous magnetic rings can suppress frequencies as low as KHz, manganese-zinc ferrite can usually suppress frequencies above MHz, and nickel-zinc ferrite can suppress frequencies above hundreds of MHz.

【Key Point】: The higher the magnetic permeability of the ferrite magnetic ring, the greater its impedance at low frequencies and the smaller its impedance at high frequencies.

-- Selection of Magnetic Ring Dimensions

The size of the magnetic ring is also a key point to be focused on during the selection process. Generally, the diameter and length of the magnetic ring need to be chosen based on the diameter of the cable and the size of the space. Moreover, factors such as the installation method and the fixed position of the magnetic ring should also be considered. In terms of appearance, choose a magnetic ring that is "as long as possible, as thick as possible, and with an inner diameter as small as possible". That is, the longer the magnetic ring, the better, and the tighter the combination of the hole diameter and the cable it passes through.

【Key Point】: When there is a DC or AC bias, the magnetic ring may experience saturation. The larger the cross-sectional area, the less likely it is to saturate.

Clasp-type magnetic ringCircular magnetic ring

-- Applications of Magnetic Rings

The magnetic ring is widely used in VGA cables, AV cables, and other high-frequency analog signal transmission lines.

The application of magnetic rings in noise suppression of signal cables

【Application Instructions】The magnetic ring is used to suppress noise interference in high-frequency VGA cables, high-speed HDMI cables, USB cables, and other types of cables.

-- Application Notes for Magnetic Rings

The filtering effect of the magnetic ring is not only influenced by the selection of the magnetic ring itself, but also by its installation position, the number of windings, and the winding method. The magnetic ring is a fragile item, so care should be taken during use to prevent damage.

-- Installation position of the magnetic ring

Place the magnetic ring near the port.

The magnetic ring has the effect of reflecting certain noise frequency points, thereby blocking the path through which the noise frequency points couple outwards via the cable. When installing the magnetic ring, it should be placed as close as possible to the source (the inlet and outlet of the cable) to achieve the best filtering effect.

The application of magnetic rings in noise suppression of AC power lines (with 5 turns of winding)

Theoretically, the more turns of the magnetic coil, the better the suppression effect. However, in practice, the parasitic capacitance also increases with the increase in the number of turns. The parasitic capacitance reduces the high-frequency suppression effect of the magnetic ring. The magnetic ring is used to suppress low-frequency interference. It is recommended to wind 2-3 turns. Use the inductance to suppress noise interference. For suppressing high-frequency interference, the magnetic ring should not be wound with wires as much as possible. Simply place the magnetic ring on the cable and choose a longer magnetic ring.

The application of magnetic rings in noise suppression for DVI cables (magnetic rings are placed on the cables)

【Notes on Magnetic Coil Winding】

For noise filtering of signal cables, magnetic rings are usually not wound in turns. A magnetic ring with an inner diameter that is compatible with the diameter of the cable is selected. The longer the length of the magnetic ring, the better the suppression effect. For noise filtering of power lines, magnetic rings are usually wound 2 to 5 times. Generally, the filtering effect is better. The wall thickness of the magnetic ring is more effective than a thinner one.  When used for 3Pin (L/N + PE ground wire) AC power line filtering, the L and N wires should be wound separately in magnetic rings, and the PE ground wire should also be wound separately in magnetic rings, or all of the L, N wires and the PE ground wire should be wound together in magnetic rings.  To suppress the frequency range of 150KHz - 30MHz, it is the way of winding the L and N wires separately in magnetic rings. The material of the magnetic ring is preferably amorphous magnetic ring, and manganese-zinc ferrite magnetic ring is the second choice. For suppressing the frequency range of 150KHz - 30MHz, sometimes the way of winding the PE ground wire separately in magnetic rings is chosen, and the number of turns should be set according to the interference frequency point.  For frequencies above 30MHz, usually the L and N wires are wound separately in magnetic rings. The material of the magnetic ring is preferably manganese-zinc ferrite. Generally, 2 to 3 turns of winding are sufficient. In special cases, the PE ground wire should be wound 2 to 3 times.

—— Fixing of the magnetic ring

The magnetic ring is a fragile item, so proper fixation is required during installation to prevent it from breaking due to collisions during transportation. Methods such as using cable ties to fix the magnetic ring, using screws for fixation, using magnetic ring sleeves for fixation, or using pipe sleeves for fixation can be employed.