MOTORS, DRIVES & CONTROLS
SESTEPPEROR I
n today’s industrial marketplace, it can be challenging and confusing when choosing the correct motor for an application. As well as all the different types of motor, the information provided on each is often either too basic or too technical to be helpful. Here, we describe the differences between stepper and servo motors and when it is appropriate to use each technology.
A stepper motor is a type of brushless DC motor. Tey are designed to provide a certain number of defined steps per revolution. For example, a motor with 200 steps/revolution will offer a position resolution of 1.8°/pulse (360°/200 pulses).
Each time the motor is pulsed by the stepper controller, it will move in the forward or reverse direction according to the number of pulses received. In the stepper example above, 100 pulses would cause the motor to rotate 180°.
ADVANTAGES OF STEPPER MOTORS A stepper motor is able to offer open-loop positioning, which is a big advantage compared with open-loop induction motors, which are not able to provide positioning. Most stepper motors do not include any feedback, which lowers the overall cost of a stepper and control solution. Teir low cost is a primary
RVOMOTOR? Mike Keefe advises how to decide which option is right for your application
reason for their widespread use. One advantage in industrial applications is that a stepper motor can be run with a DC-powered stepper drive. Tey do not require larger inverters that input 230/460VAC or bulky fusing and cabling, which can be quite significant with multi- axis applications.
LIMITATIONS OF STEPPER MOTORS It is possible for a stepper to ‘lose’ position. Tis can happen if the stepper motor does not provide sufficient torque to move the shaft and load. It can also happen at high speeds where the stepper motor goes too fast to lock in at each step. Tis could also happen if the inertia of the load carries it past the intended step when it is stopped. If the position accuracy of the stepper is critical, some motors will add feedback such as an incremental encoder. Te feedback will identify if the
Combivert F6 drives
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