well, im no engineer, but just assuming that the nema starter could be replaced with a vfd would be premature right? certain things like length of conductors, amount of conductors in raceway, etc...like i said im no expert, i always consult an EE on these types of projects. its my experience with said EE that ive learned that standing waves generated by the switching of the vfd that can destroy a "standard duty" motor where an inverter duty would withstand the higher "spikes". and also might one need line side reactors and load side "chokes" depending on the application right. like i said, im no expert on this application, therefore i do what OP is doing. ask questions. the drive manufacturer could also help right?