It is somewhat unusual to “upgrade” to a lower-voltage electric service, although 208Y/120V is admittedly more modern and typically readily supported by utilities in commercial neighborhoods and smaller institutional facilities.
Demand kVA of the existing 230V equipment is not mentioned, and may affect the following suggestions. Where 240V service is to be maintained, there may be two approaches.
Acme Electric group B or federal Pacific T242T-S transformers at 240—208Y/120 volts may permit a 240V 3ø separately derived system. It is likely that the drytype manufacturer would recommend that the transformer 208Y/120 X0-neutral terminal be left unconnected to prevent circulating currents in the local wye winding. Primary and secondary overcurrent protection would be needed per NEC 240-3(e)&(f)+, 450-4+ and others.
Another possibility is three wye-connected 120x240—16/32 volt boost autotransformers, from the same manufacturers. Nota Bene for wye-autotransformer application—the 208Y/120 circuit MUST carry the neutral from the source to autotransformers’ common-connected shunt windings, but with NO neutral extended to downstream equipment or loads—as phases will operate at ~139V to neutral/ground. NEC 450-4+ and others reference autotransformer application. Effectively it will be a 240Y/139V system.
Keep in mind that in both cases 150°C-rise transformers typically run blistering hot when approaching nameplate load. In both cases, dedicated 240V 3ø distribution should have distinctly different and readily identifiable color coding for phase conductors— critical to avoid damage and load imbalance.
1ø 230V motors might be ‘staggered Aø-Bø, Bø-Cø and Cø-Aø on the 240V 3ø system (with no attempt to connect 115V devices.)