A method for BH curve identification of the magnetic core of synchronous reluctance machines is presented. It starts from the knowledge of machine torque or phase voltages measured at normal operation with ac balanced currents or obtained from dedicated experiments proposed for the BH curve identification. The identification is formulated as an inverse optimization problem where the experimental data based on appropriate experiments serve as the inputs and the BH curve parameters represented with a closed-form expression as the optimization variables. The influence of the different types of measurements on the identified parameters and the optimization process is discussed and compared. Moreover, the impact of geometrical uncertainties due to manufacturing tolerances is investigated and addressed. Virtual measurements obtained from finite-element simulations are used for the study. It is shown that the proposed method can identify the BH curve of the machine core with good accuracy.