Design and performance of compensated reluctance synchronous machine drive with extended constant power speed range

Reluctance synchronous machine drives are known to be efficient, however are also known to have a poor constant power speed range. Interior permanent magnets are normally used in the reluctance synchronous machine to improve the constant power speed range. In this paper an alternative reluctance synchronous machine drive that extends the constant power speed range without using permanent magnets is proposed and investigated. In the proposed drive the DC-link current is used through a compensating or assisting field winding on the rotor. The analysis and design aspects of such a reluctance machine are presented in the paper. The results show, amongst others, that the proposed drive can generate constant power up to 3.5 per unit speed and improve the power factor of the machine in certain cases by more than 20%.