Assessment of Electromechanical Conversion Efficiency in Synchronous Reluctance Machines

A comparison of various synchronous reluctance machines is performed in terms of the electromechanical conversion efficiency. The efficiency criteria are as the specific electromagnetic torque, active and total power consumed, and power factor. A generalized mathematical model is proposed, which is based on the principle of electromechanical transformation, being a change in the magnetic energy of all windings, as a function of the rotor rotation angle. The assumptions of the model are that the electric machine is not saturated, the magnetic conductivity of steel is infinity, and there are no scattering fluxes. This model made it possible to obtain performance indicators of electric machines with an established error under any control actions and for various configurations of magnetic systems of the active part up to the nominal values of speeds and torques. Calculation of the efficiency indicators of a synchronous reluctance (reactive) machine with a toothed rotor is carried out under the assumption that the current of the stator winding is distributed along the air gap according to the harmonic law, the stator serration is not taken into account, and the average rotor conductivity is taken to be unity. It is shown that it is appropriate to operate a gearless electric drive on the basis of a synchronous reluctance machine with a double serration, which is due to the high specific torque, but the range of regulation of such an electric drive in terms of speed in the second zone is limited due to the small power factor.