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Design considerations of a direct drive servo motor will be presented in this paper. The application is a turret platform for remote weapon stations where low speed and high torque are the major requirements along with low cogging and pulsating torque. Motor outer envelope dimensions are dictated by the application's geometric restrictions. Design process of other internal dimensions and parameters has been introduced. The sensitivity of the motor performance based on the dimensions has been analyzed. Finite element analysis and experimental results have been provided. The motor has also been compared with an off the shelf motor which can be adopted for the same application. Two designs have identical outer envelope which includes stator outer diameter and active axial length. The main difference between the peculiar and the off the self motor is the winding. They have concentrated and distributed winding respectively. Studies show that two motors have comparable torque constant for rated loading conditions. Under heavy load conditions, designed motor yields higher torque constant. Thermal analysis results also revealed that designed motor has lower temperature rise than off the shelf motor. The paper tries to shed light for the reasons of such performance discrepancies between two motors with the help of finite element and experimental analysis.

Permanent magnet (PM) synchronous motors have found numerous applications over the last two decades due to their high torque to weight ratio and efficiency. However, one of the main drawbacks of the PM motors is the magnet corrosion. This paper investigates the influence of magnet corrosion on the performance of surface mounted permanent magnet motors. Uncorroded and corroded magnet rotors are used to investigate the motor performance including voltage and torque constants. It has been found out that the corroded rotor does not degrade the motor performance even after the intense corrosion tests if good quality NdFeB magnets are used.