Brief Introduction to A Common Mode Choke

When working with electric circuits, issues of electromagnetic interference (EMI) and radiofrequency current (RFI) pose serious threats to equipment. Whether you are working with alternating current (AC) or direct current (DC), high frequency signals can threaten the functionality of your circuit. As such, a common mode choke can be used to suppress interference from the power supply. For your better understanding of the benefits a common mode choke could offer your industrial, electrical, and other applications, this blog will explore the working principles of this unique electromagnetic component.

Comprising two wires wrapped around a ferrite core or magnetic core, a common mode choke gets its name from its ability to “choke” high frequency signals, while allowing low frequency signals to pass through. This function is accomplished through the combination of two fundamental processes. By steering the noise current in the same direction across both wires, while simultaneously generating a magnetic field with two or more windings, a common mode choke blocks the common mode current. This in turn adds flux and prevents frequency noise to the circuit.

Noise in circuits is classified as either differential mode or common mode, depending on the relative location of the input sides through which the current enters and exits, and a common mode choke works for either type. Common mode noise occurs when input sides enter and exit through the same direction and return through a common ground, while differential mode noise occurs when input sides enter and exit through opposite directions. As such, it is important that the transmissions generate magnetic fields that are equal in magnitude so they may sufficiently cancel out or add together.

In a common mode choke, the differential mode current produces equal and opposite magnetic fields as it passes through the choke’s windings. Meanwhile, the common mode current creates equal magnetic fields that add together to impede and attenuate the current flow. As such, when you are looking to protect your systems from interference and noise, turn to Internet of NSN to procure all of the common mode chokes and other electronic equipment you require.

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