New studies related to the improved performance in the stepper motor for Solar Array Drive Assembly (SADA) for Indian Remote Sensing (IRS) satellites

This paper presents the design, analysis and development of 720-step high torque stepper motor for the Solar Array Drive Assembly mechanism used in IRS class satellites. The existing motor develops a peak holding torque of 1.1 Nm at 42 V with magnetic saturation and the torque pattern has the third and fifth harmonics in addition to the fundamental component. The stepper motor magnetic circuit design is optimized with FE Tools to obtain the maximum torque and make the torque pattern free from spatial harmonics without any change in overall envelope, which is implemented in the verification hardware. It is found the desaturation model develops a peak torque of 2.6 Nm as the magnetic saturation is eliminated. With the increase in permanent magnet excitation and change in tooth profile the peak torque is further improved to 5.1 Nm. The torque pattern is smoothened by providing unequal tooth pitch in stator and rotor.