Experimental Study of Torque-Ripple and its Effect on the Flux Weakening Range of Synchronous Reluctance Machines

Synchronous reluctance motors (SynRMs) exhibit a high rotor anisotropy in order to obtain a performance comparable to that of permanent magnet synchronous motors. The air-gap flux density is not sinusoidal due to the stator slots and rotor flux barriers. The non-sinusoidal distribution of the air-gap flux causes torque-ripple in the synchronous reluctance machine. This paper proposes an experimental method to measure the torque-ripple of the synchronous reluctance machine at static conditions. The proposed method is used to study the torque-ripple of two similarly sized synchronous reluctance machines. Experimental results are presented for the torque-ripple at various operating conditions including extended speed region. It is found that the percentage torque-ripple for SynRMs increases in the extended speed region. The effects of torque-ripple in this region is experimentally studied, and it is found that the torque-ripple places a limit on the torque-speed range of the motor.