This paper describes a technique to generate Pulse Width Modulation wave forms, based on space vector theory, using a three level inverter topology for controlling AC motor Drives. Particular emphasis is dedicated to the analysis of the different operational modes, i.e. asynchronous mode, synchronous mode, 12 step (quasi square wave form) and on the transition between different modes; the theoretical solution adopted for the problem of minimum pulse dropping, for the control of midpoint voltage, and for the compensation of delay time is explained. The practical implementation, based on a 16 bit microcontroller is illustrated, and the experimental results obtained on a 33 kVA inverter IGBT are presented.