<p>This paper presents an advanced optimization-based fault-tolerant control strategy for dual three-phase permanent magnet synchronous motor (DT-PMSM) drives operating under open-phase and short-circuit fault conditions. The suggested approach systematically addresses the interplay between torque production and single-phase copper losses, while proactively managing thermal constraints to prevent overheating. To enhance the efficiency of the current optimization process, a novel objective function is formulated, leveraging the Lagrange multiplier method to derive maximum-torque current references. In contrast to conventional fault-tolerant methods that impose rigid constraints, such as maintaining sinusoidal current waveforms, the proposed approach flexibly utilizes Lagrange optimization to explore optimal solutions without unnecessary limitations. This enables the attainment of maximum theoretical torque output while minimizing overall copper losses. Moreover, the Lagrange-based optimization framework facilitates balanced torque production and copper loss management under fault scenarios, ensuring high-efficiency fault-tolerant operation. Experimental validations confirm the advantages and robustness of the suggested approach, demonstrating its capability to sustain high torque output and minimize copper losses under open-phase fault conditions. These observations confirm the feasibility of the designed approach to significantly enhance the reliability and operational performance of DT-PMSMs in demanding industrial applications.</p>