Maximum Torque-per-Ampere Control of Double Salient Motor Based on nth-Order DQ Coordinate Transformation

Based on a Fourier linearized mathematical model of doubly salient motor (DSM), the linear relationship between harmonic currents and the average torque in the n<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup>-order dq rotating coordinate system is derived. The obtained linear relationship is then utilized to derive the conditions for the DSM to achieve the maximum ratio of the average torque to the RMS value of the current. Finally, a Maximum torque-per-ampere ratio (MTPA) control based on the n<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup>-order dq coordinate transformation is proposed, and experiments comparing it with the commonly used square-wave current control are carried out on a 12/8 electrically excited DSM. The experimental results show that this control method improves the torque-per-ampere ratio of the DSM and also suppresses the torque ripple compared with the square-wave current control. The correctness of the derivation and the superiority of the control method are experimentally verified in this paper.