Design of direct-drive permanent magnet synchronous motor for cryogenic valve

This paper presents a novel design of a low-speed and high-torque cryogenic direct-drive PMSM. A new simplified model is proposed to address the inaccuracy of the electro-thermal coupling model of the common cryogenic PMSM design. The coupling model focuses on the influence of the winding copper loss on the resistance, which improves the accuracy of calculating the temperature distribution and resistance value. Compared with FEM, the error of the calculation results is 4.8%. A new design method is proposed to address the problem that the common low-temperature PMSM designs lead to a rise in the copper loss. Measuring the improvement of the magnet performance in low temperature, the method reduces the turns of the coil, which significantly reduces the amount of copper loss. Compared with common methods, the amount of copper loss reduces 29.5%. Furthermore, a prototype is fabricated and tested, the results of which verifies the rationality of the design.