Contributed Article: Seven Characteristics of Stepper Motors

Nick Jakubowski over at Circuit Specialists has submitted an article outlining the main characteristics of stepper motors and how they work. Read on for the full article below.

A stepper motor, also known as a step motor, is a brushless electric motor that divides a full rotation into a large number of steps. These devices come in many different sizes, speeds, and phase current waveforms. Unlike DC brush motors, which operate when voltage is applied to their terminals, stepper motors have gear-like electromagnets arranged around a piece of iron. An external control current energizes the electromagnets, this is also known as a micro-controller. The gear’s teeth magnetically move the electromagnet teeth, step by step, which is where the name derives. There are seven characteristics of stepper motors;

1. They are considered constant power devices.
2. When the motor speed of the stepper motor increases, the torque will decrease. Often the most torque is exhibited when the motor is in a stationary state.
3. The torque curve of the step motor can be extended by implementing a driver and increasing the driving voltage. These are known as chopper circuits and often driver chips can be found in many stores which makes the this process much simpler.
4. Stepper motors tend to be a bit more noisy compared to DC motors. When a step is made on the motor, the rotor will snap from one position to the next which makes the motor vibrate.
5. At some speeds the vibrations can become so bad the motor may lose torque or direction. This happens because of the rotor which is being held in place by a magnetic field. Each step the motor takes, the rotor overshoots and bounces back into place. This can cause the step motor to jump, changing its position and altering its direction.
6. Issue number 5 can be easily mitigated by simply accelerating quickly through the problem speeds range. Another solution is to physically dampen the system. Using a micro-stepping motor will also solve this issue.
7. Stepper motors that have a larger number of phases will have a smoother operation, much like micro-stepping motors.
8. These devices are excellent in many applications, and their simplicity makes them very popular among hobbyists. Some common uses for stepper motors include; slot machines, compact disc drives, computer printers, flatbed scanners, and so on. With different phases, drive circuits, and commercial uses, it is clear to see why they are used so often.

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