How to Select Servo System in Few Steps

Provided one chooses the correct servo system, incredible performance, accuracy and speed will be the on their way soon. On the other hand, failing to choose the right kind of servo motor will prevent you from attaining a flexible and constant servo motor drive with rather poor accuracy. In order to avoid such inconvenience, one should be aware of the essential factors that contribute to making the right choice and pick wisely among the different types of servos available out there.

Voltage and Motor Speed

The power of the equipment is the first indicator that points towards the quality of what you’re considering to buy. The servo models available come in 100, 200 or 400 VAC, all of them compatible with either single or three-phase power. Servo motors are meant to perform repetitive actions, therefore their speed profile should be carefully considered. The speed at which the given servo is able to perform should match the requirements for your application.


Torque is the strength that a servo produces in order to be able to rotate. It can be derived from three main sources: the inertia of the mechanism, external forces that press again each other or gravity itself. As you can probably note on your own, the sources that we listed aren’t actually measurable. Calculating each one of them as accurately as possible is still much recommended. You should calculate the inertia of each mentioned segment and them simply add the values. The acceleration is ought to be multiplied by the load inertia in order to determine the torque. All above mentioned values such as gravity and friction should also be added to the final torque calculation. If you can make use of software tool, you can also utilize a root-mean-squared calculation (RMS).

Calculating the Inertia Ratio

When it comes to servo sizing, one might consider overlooking the inertia ratio at first at the expense of other more significant calculations, however, this is a mistake only made by newbies, so bare in mind not to take part in it. Experienced users will tell you that the Inertia Ratio is in fact important enough to be one of first things that the user should determine. It represents the ratio of the inertia of the load divided by the inertia of the motor’s rotor that is then divided by the gear reduction’s square.

Choosing the Motor

Once you’ve completed determining all previously explained steps, the actual motor choosing should take place. All you need to do at this point is to browse for the right one, consulting with the requirements you’re already informed about. The drive is supposed to correspond with the supply voltage, the rotor inertia is to satisfy the the requirements for the servo drive you’ll be using. If you cannot find a perfect of at least a close match, you can rely on a concept called gearing and thus attain constant servo motor drive. Through gear reduction you will be able to match the servo to the load by speed reduction, torque increasement or inertia ratio lowering.