Stepper Motors vs. Servo Motors

Step motor systems have unique characteristics such as smooth motion, stiffness at stand still, easy setup, and low cost. Popular for decades, these systems continue to be a widespread choice among design engineers.

Advantages of Stepper Motor Systems vs Servo Motor Systems

Step motor technology provides several advantages over servo motor systems. One of these is inherently lower cost as compared to servo motors due to step motor construction. Step motors do not require tuning, allow for greater inertia mismatch and have a very high torque density. Because this torque is 100% available immediately upon startup, step motors can be very advantageous for applications requiring short, quick moves or when coupled with high inertia loads.

In addition, since step motors are synchronous motors with a high pole count, they are able to run smoothly at extremely slow speeds with minimal torque ripple. Both servo and step motors share a common identity as permanent magnet synchronous motors; however, there are differences that impact how the motors perform. For example, brushless servo motors typically have (2) to (8) magnetic poles on the rotor, whereas the 1.8 degree step motor has (50) poles. Due to this pole count difference, the step motor is, in essence, electromagnetically geared down as compared to the servo motor, allowing for better low end torque performance and positioning capabilities.

Disadvantages of Stepper Motor Systems vs Servo Motor Systems

As with any technology, there are also some disadvantages associated with use of a step motor system. The most critical drawback is the loss of synchronization and torque (stall) if a large load exceeds the motor’s capacity and its ability to resynchronize once the load is reduced to a level within the motor’s capability. In addition, step motors tend to run hot due to use of full phase current, independent of load.

In many cases, these disadvantages, along with the limitations associated with available ‘bridge’ technology to overcome them, may have influenced the decision to choose higher cost servo technology rather than traditional step motor technology.

Bridging the Gap Between Servo, Brushless DC, and Stepper Performance

THAT IS, UNTIL NOW…. ServoTrack™ closes this ‘bridge’ technology gap and provides a closed loop stepper system by eliminating unintentional stalling due to transient loads, or excess friction, and enabling torque control as an integral function of your stepper system.

Learn more about whether our ServoTrack™ solution is right for your specific application.