Basic EMC/EMI / RFI Filter Configurations

Filters can be described by their basic LC configurations.  Filters are typically described in this way because these are the primary filtering components.
The major filter configurations are:
Pi, LC, CL, T, Delta and Wye

The first 4 are Single Line configurations described by their series inductors and ground capacitors while the latter two are three phase configurations typically described by their line arrangements.

General Filter Configurations
A Pi filter consists of an inductor with a ground capacitor on both the input and output.  Pi filters present capaciative terminal characteristics which are desirable when connecting to inductive sources and loads.
An LC filter is an inductor (L) followed by a ground capacitor (C).  LC filters present an inductive load to their source and a capaciative source to their load.  This makes them particularly suited for mating capaciative sources with inductive loads.
A CL circuit is the reverse of an LC filter.  CL filters have ground capacitors at their inputs and series inductors at their output.  CL filters are typically used to connect inductive sources to capaciative loads.
A T filter consists of a ground capacitor with a series inductor on both sides.  T filters are typically used to connective inductive sources to inductive loads.
Three Phase Power Configurations
 Three Phase power systems may, or may not contain a Neutral return.  A Three Phase system without a Neutral phase is referred to as a Delta configuration.
 Three Phase power systems that have a neutral return line are called Wye (or Y) configurations.

For more aggressive filtering, more complicated circuits can be used by connecting filters in series, these configurations are listed in the order they appear from input to output.
Such a filter would work well with an inductive supply and load.

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