Basic Concepts of Stepper Motor


Let us take a sneak peek into Stepper motors and learn their basic functioning and certain technical terms, which are generally associated with them. Though this article is meant for everybody, it is primarily meant to educate our young readers and hobbyists alike. So lets begin:

Basically, we will be talking about the Hybrid Stepper motors, which as the name indicates are a Hybrid of “Permanent Magnet” and “Variable Reluctance” stepper motors. The Permanent magnet stepper motors, also referred to as “Tin-can” motors are low-cost, low resolution type motors with step angle ranging from 7.5-15 degree.(48-24 steps/revolution) this is easy maths, try it yourself!! PM motors have permanent magnets added to the motor structure. The rotor has no teeth, but is magnetized with alternating north and south poles, and is situated ina straight line to the rotor shaft. These magnetized rotor poles provide and increased magnetic flux density and because of this, the PM motor exhibits a higher torque as compared to a Variable Reluctance type.

The Variable reluctance motors consist of a soft-iron multi-toothed rotor and a wound stator. When the stator windings are energized with the DC currents, the rotor poles become magnetized. Rotation occurs,when the rotor teeth get attracted to the energized stator poles. The Hybrid motors are a combination of these two technologies, and provides a better performance compared to torque, resolution and speed. Typical step angles for the Hybrid stepper motors range from 3.6-0.9 degrees(100-400 steps/revolution). The rotor is multi-toothed like VR motors and contains an axially magnetized concentric magnet around its shaft. The teeth of the rotor provide an even better path for the magnetic flux to go to preferred locations in the air-gap. This further increases the detent, holding and dynamic torque characteristics of the motor. Continue reading