During the last 50 years the global electricity consumption has been grown about four times. Many sectors are involved in this trend: industrial, residential, transport, commercial, public services and so on. Following this trend, the global policy makers are encouraging variable speed drives (VSD) for higher efficiency. Moreover, all manufactures are moving on reduction of final price of VSD: elimination of speed/position transducer permits to achieve this target, improving also reliability. This thesis discusses the sensorless control of VSD, in particular, a PM-assisted synchronous reluctance motor. The method adopted is based on two stages: I-f control and sensorless FOC. The former is an open-loop speed control, used only to start and stop the drive, where amplitude and frequency of the imposed reference current vector are properly set: constant amplitude and ramp variation frequency.