Step, stepper or stepping motors are all names for brushless DC electric motors which work by dividing a full motor rotation into several equal steps. This enables the motor to move into position and hold there without any requirement for position sensors. Provided the motor is carefully programmed for its application, each step position can precisely govern the required torque and speed.
Stepper motors are digital input-output devices and are controlled with digital pulses provided from the stepper motor controller. Stepper motors have multiple electromagnets positioned around a central gear-shaped iron core. These magnetically attract the teeth of each gear in turn and rotate the motor by a precise angle. A digital pulse from the controller moves the motor to move one increment one angle of motion, the increment is precise and the same every time, multiple digital pulses cause the movement to change into a continuous rotation. If a stepper motor were connected to an alternating current, the stepper motor would rotate continuously.
Stepper motors are used in applications where the complexity of a servo motor is not required; examples include; pick and place, winding tools and machine tools. Choosing a stepper motor requires the designer to know the torque and speed of the application. Once the torque and speed are known these can then be compared against the manufacturer's torque-speed curve for correct stepper motor selection. Stepper motors are available in three basic forms; permanent magnet step motor, variable reluctance stepper motor and a hybrid stepper motor that is a combination of both permanent magnet and variable reluctance stepper motors. The stepper motors from Festo are all hybrid stepper motors.