An improved structure for hybrid stepper motors to increase the torque density

Stepper motors are actuators used in a variety of devices, including robots and CNC machines. Hybrid stepper motors (HSMs) tend to be the most popular of all stepper motor types due to their high torque density. A new structure for HSMs is presented in this paper, which significantly improves torque density. This improvement is based on changes in the magnetic flux path in the stator. In conventional stepper motors, magnetic flux must pass a quarter of the stator to complete its path. But, in the new design, this route is reduced to a small section of the stator. Moreover, the used space in the motor is optimized. It means that the teeth in the rotor and stator are longer. The rotor diameter also has become bigger. Investigations proved these changes are dramatically effective in increasing motor performance. To assess these improvements, a conventional hybrid stepper motor with the same volume is chosen and modeled. Both of these two motors are simulated using Ansys Maxwell software. Comparing their results proves that the torque density in the new motor structure has increased by more than 200%.