Hi uswt
Contactors are normally used for this application.The
PLC card outputs,will trigger a relay that in turn may energ/deenrg your contactors.This application will require that contactors probably should have a mechanical interlock to make sure that the 2 contactors are not energized simultaneously.
If the Generator is large,you might have to use control relays to operate the larger contactors.
PLC card Output relays contacts may be limited to inductive loads of 5 amps,10 amps or less amps.
Take care
GusD