What is a Converter Transformer?

Take a look at this page.

Convertor Transformers are used in HVDC stations.

They are connected to the HVDC Valves on one side and AC switchyard on the opposite side.

Consequently, the insulation of these transformers have to withstand AC voltages superimposed by DC voltages ( on polarity reversal). Hence a different design of insulation to withstand AC+DC stresses.

Due to harmonics being reflected back into the AC yard from the convertor side, addtional stray and eddy current losses in conductors and body / tank, the conductor selection and cooling arrangement selection is different than ordinary power transformers.

The bushing connected to the DC side has a different design.

All in all this is an entirely different transformer.

You can please refer to HVDC books for further exploration.

best wishes

Deepak