Design Optimization of PM Synchronous Motor: Rail Mounted Belt Drive Elevator Systems

In this article, the design and optimization of 4.5 kW inner rotor permanent magnet synchronous motor (PMSM) with 400 rpm nominal speed was carried out for belt drive elevator systems. Unlike traditional methods, the integration of the motor into the elevator carrier system is provided directly on the rails. Thus, high cost and complex machine chassis constructions are eliminated. The elevator loads accumulated on the machine were properly transmitted to the building and the ground. The electrical and magnetic modeling of the PMSM was carried out considering the volume constraints that emerge according to the mechanical design. The two most important criteria to be considered in elevator traction motors are providing high efficiency and passenger comfort. In line with these objectives, a design with efficiency above 91% and torque ripple below 1% is presented. Based on the acquired limit values and using the finite element method (FEM), the optimization of parameters such as the slot opening, magnet thickness, embrace, stator tooth thickness, and air gap was conducted via genetic algorithm. In addition, step skewing of magnets was applied to the optimized model to reduce torque ripple. According to the results, 18 slot-20 pole PMSM with 0.61% torque ripple and 90.97% efficiency has been obtained. The designed PMSM was produced and tested using an electrical motor test setup. Based on the test results, the efficiency and cogging torque were obtained as 89.98% and 0.78 Nm (pk2pk), respectively. Thus, the FEM analysis solutions are verified by the test results.