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How are Ferrite Cores effective in EMI Suppression in Cables?

Ferrite cores in cables

Ferrite cores are magnetic cores that are used widely in electric transformers and inductors. They are made with ceramic materials and produced in a variety of shapes and sizes. As ferrite cores have high magnetic permeability, the ability to reduce losses in high-frequency, and low conductivity, these properties help them reduce noises and common mode currents in electric devices.

In this blog, we’re going to explore how ferrite cores work effectively for EMI suppression in cables.

Why Ferrite Cores are used for EMI Suppression in Cables?

Ferrite cores are used for noise suppression in electronic devices. They are an effective way of combining high-frequency resistance into a cable to minimize common mode current and radiation. Generally, they are used in keyboards, mouse and PC cables.
In addition, power supply cables also use ferrite cores when a device is powered by an external transformer or any other supply.

The core acts like a common mode choke and helps in minimizing the conducted and/or radiated emissions from the cable. They also help to suppress high-frequency pickup in the cable. Basically, ferrite cores work as high-frequency resistors with no impedance at direct current or low frequencies.

They are most significant in providing attenuation of unwanted noise signals over 10MHz. However, they are not much useful for low-frequency cable emissions, under 10MHz because their impedance is quite low to perform at these frequencies. The impedance of ferrite cores can be increased using several turns, but this results in increasing interwinding capacitance and degrading high-frequency of the cores.

Specifications & Significance of Ferrite Cores

The performance of ferrite cores in removing electromagnetic interference varies as per their materials and shape. It is owing to the fact that the magnetic permeability changes according to the materials, the impedance is also different.

The ratio between the resistance component and reactance component also depends on the use of ferrite materials. However, the properties of ferrite cores usually remain the same regardless of the ferrites.

How Ferrite Cores Minimizes Common Mode Current?

Common Mode Current is a part of conductor currents that cause multi-conductors to work like a single conductor. It helps to determine the conducted interference or radiated interference which occurs in an electrical device due to high unwanted field emissions.

It is developed in two conductors that have equal or opposite current in the same distance. If the distance is higher, there will be no common-mode current as the electric and magnetic fields induced in the wire cancel each other in the core. Hence, if there’s no magnetic field, there’s no inductance or impedance.

To minimize the common-mode current, the conductor is fastened with the ferrite core, making an inductor. So, any current will induce a magnetic field in the core like a normal inductor. Hence, you get the advantage of increasing frequency along with increasing impedance.

The process is known as common mode choke, which shows a high impedance to common mode currents and a low impedance to differential mode currents. The high impedance of the choke prevents the development of common mode currents. Ferrite cores used for this purpose have low losses, hence common mode voltages are transformed into heat in the cores.

Most of the failures happen because of the common mode current in cables and wire assemblies. This current can also return through an alternate route that could be adjacent cable, a ground plane, or any other unexpected route. Common mode currents follow the route of least resistance in a circuit.


Ferrite cores are a perfect choice for noise suppression in cables. They help to improve the performance of power supply cables and make them ideal for several electrical requirements. Cosmo Ferrites manufactures ferrite cores with impeccable quality to suppress electromagnetic emission problems in cables. To know about their effectiveness and use of your application, you can contact our team for guidance.