(Optimized) icon next to it.The Core Selection form displays the list of the available transformer cores. The transformer cores are displayed in ascending order of their output power. The Active Core Parameters are updated according to the core selected in the list. Cores that are non-preferred are identified with "[NP]" placed at the end of the Core Type name and excluded from optimization. If you want to use a non-preferred core during optimization see Transformer Selection and Manual Design.
PI Expert adds a transformer core automatically when creating a design. If the core used in the design has been selected by the optimization engine, it displays the (Optimized) icon next to it.
If you select a different core from the list including a non-preferred one, PI Expert will place the 
icon next to it. If the core you select is too small for the amount of power that the supply is specified to deliver, PI Expert will place the 
(Undersize) icon next to it.
Click the Auto Pick button, and PI Expert will select the smallest core which meets or exceeds the continuous output power requirements and places the 
icon next to it.