Question: are all motors vfd compatible?
Answer: If the Motor is pre-EPAct (1992), it should be run on VFDs only with careful consideration. Motors made during that time were not made for VFD use, but if they are VFD rated, will be okay. Class F insulation or higher is suitable for VFD use, but VFDs may have no more than a 2:1 Constant Torque ratio.