With an ideal common mode choke coil, magnetic flux caused by common
mode current is accumulated inside the ferrite core. Therefore, the
common mode choke coil works as an inductor against common mode
current. On the other hand, magnetic flux caused by differential mode
current cancels out. Therefore, a common mode choke coil does not
affect differential mode current.
However, since an actual common choke coil produces leakage flux,
magnetic flux caused by differential mode current does not entirely
cancel out. In other words, an actual common mode choke coil contains
differential mode inductance as well as common mode inductance. |
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