What is the difference between a common mode inductor and two separate coils?

Common mode inductors, two separate winding coils and two groups of coils are mainly reflected in the following three different aspects:

Appearance and process operation: Double wire winding is to overlap two wires along the magnetic core and wind the wire, the process operation is relatively simple. The two winding is the two winding is separated, each side of the magnetic core along the magnetic core close to 180° half winding, the process operation is more complicated.

Leakage inductance and distributed capacitance: The leakage inductance of double wire and wound is smaller, but the capacitance value between the two groups is larger. The leakage inductance of two separate winding is larger, but the capacitance value between the two groups is smaller.
Filtering effect: In specific application scenarios, choosing double wire and winding or two winding separately will have different effects on the filtering effect. For example, in some scenarios, two-wire parallel winding is more suitable for "common mode + differential mode" filtering, while two-winding separately is more suitable for "common mode + common mode" filtering
What are the characteristics of the two winding methods?

1. Double wire and wind

Small volume, make large sensitivity, filter medium and low frequency.
There is a small differential mode inductance
High coupling capacitance
There is a small leak sensation
2, the two groups of coils are wound separately

• Large volume, small sensitivity, high frequency filtration.
• There is a small equivalent distributed coupling capacitance
• There is a high leakage sensation
• Therefore, the winding method should be selected according to the actual application. In the selection of common mode inductors, it is necessary to decide whether to use double wire and wind or two winding separately according to the specific application scenario and design requirements.

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