In the field of electronics, a choke is defined as an inductor which is used to block higher-frequency while passing Alternating Current (AC) of lower frequencies and Direct Current (DC) in an electrical circuit. A choke generally comes with a coil made up of insulated wire generally wound on a magnetic core, albeit some comprise of a donut molded "globule" of ferrite material hung on a wire. The impedance of the choke increases with the increase in the frequency. Because of the low electrical resistance, it passes both the DC and AC with a little amount of power dissipation. The amount of AC passed is limited due to its reactance.

The name “choking” is derived from blocking as it blocks high frequencies while passing low frequencies. It is a functional name. The word – “choke” is used for all the inductor that helps in decoupling or blocking higher frequencies, but the electrical component is simply known as an inductor if it is used in tuned circuits or electronic filters. Inductors that are designed for the utilization as chokes are generally recognized by not having the low-loss construction (high Q factor).

Common Mode Choke

The CMC or the Common Mode Choke, where two curls are twisted on a solitary center, is helpful for the suppression of RFI (Radio Frequency Interference) and Electromagnetic Interference (EMI) from the power supply lines. It also prevents the malfunctioning of power electronics devices. It passes both equal as well as different current while blocking common mode currents. The magnetic flux generated by differential mode (DM) currents in the solid core will in general cancel each other since the windings are negatively coupled. Thus, the choke provides little impedance or inductance to DM currents. Commonly this also suggests that the core won't soak for a huge amount of DM currents and the heating effect of the winding resistance will determine the maximum current rating. However, the CM current gets a high amount of impedance because of the summed inductance of the positively coupled windings.

CM chokes have found its use in electrical, telecommunications, and industrial applications to either decrease or remove noise and some other linked electromagnetic interference.

Whenever the CM current is conducted by the CM choke, most of the magnetic flux initiated by the windings is restricted with the inductor core because of its high permeability. Here, the leakage flux is very low. But still, the DM current which flows through the windings will produce a high amount of magnetic field as the windings are negatively coupled. A twisted winding structure is used with the CM choke to decrease this near magnetic field emission.

The difference between the conventional balanced 2 winding common mode choke and the balanced twisted windings common mode choke is that the windings cooperate in the focal point of the center open window.

This was all we have regarding Common Mode Chokes. Hope you liked going through the article. Brands that manufacture them are Kemet, Schaffner, and Murata. Make sure to check them out using the links as provided.

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