What brand of VFD are you using? Due to space limitations I cannot remote mount anything so the VFD and controls need to sit in front of the motor.
Mine are the ebay el cheapo units. About $70. If you need the VFD right by the motor, I don't recommend them on a grinder unless you put them in an enclosure. I put mine in a cabinet and use a little control box next to the motor. They will get grinding dust in them and blow. I have about 10ft of cord which gets the job done for me.