Can transformers used in solar farms to step up DC current into AC current, through the use of a rectifier, be considered to be part of this exception?

No. Even if transformers used in solar farms may, during the night, reverse the flow and convert a certain level of AC current from the transmission and distribution grid into a DC current in solar photovoltaic installations, they are not specifically designed for this purpose, and therefore cannot be considered part of the said exception. The exception is meant to cover transformers designed for use with rectifiers to provide a DC supply in certain industrial applications.

_{Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.}