Control of synchronous reluctance motors without encoder for industrial applications

The fundamental control design aspects for synchronous reluctance motors without damper circuit are discussed in this paper. To achieve a high control performance and the quality demanded in industrial environments, the impact of the motor's typical nonlinearity with respect to the control structure required is considered. Based on measured saturation characteristics, a state-space model is derived for further observer design as well as for simulating the system. Control strategies with optimum efficiency are calculated and compared. Controlling the motor at defined current- and voltage limits is an essential feature of industrial drives, and is described in detail. Finally, the last section presents a powerful method for identifying the initial rotor speed and -position for starting and for flying restarts without an encoder.