Use a less power low voltage IGBT converter to adjust speed of a full power medium voltage induction motor of fan or pump

To solve the difficulty of medium voltage variable frequency drive of fan or pump, a technique, rotor-side variable frequency drive (RVFD), is introduced that a less power (0.2-0.3P/sub N/) low voltage (<400 V) IGBT converter is used to adjust speed of a full power medium voltage (6-10 kV) motor. The features of the technique are: simple circuit, less large devices, better power factor and smaller harmonics. An improved RVFD based on PFC technique is proposed, it can remove the influence caused by diode rectifier.