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Power Transmission Distributors Association is...

comprised of companies that distribute and manufacture the components that keep your world running smoothly.

Tech Tip: Motion Control

Enhance your employees’ product and industry knowledge with PTDA’s Tech Tips. This library of online tips, hints and techniques may be used to educate new and current employees on power transmission/motion control (PT/MC) products, technologies and concepts and serve as reference and reminder for more experienced staff. Tech Tips are based on the expertise of PTDA member companies, content from Motion Control Made Simple or PTDA’s Power Transmission Handbook®, the definitive resource and training tool on PT/MC products.


Visit the full library  of Tech Tips for additional products.

What is the ideal inertia ratio between the load and the motor?

The ideal balance of the inertia of the motor and the reflected inertia is one. Although this ideal situation is typically not present or it comes at a high cost. It is therefore important that the designer calculates and compares the two inertias. The inertia-range between the load and the motor plus gearhead should not exceed 10. The higher the inertia of the load the higher the torque needed to accelerate it.

When the motor inertia is too small relative to the load, oscillations and increased settling times will occur. This results in a loss of precision and an increase in problems with servo tuning, noise, and instability. When the motor inertia is too large relative to the load, the application’s optimum cycle time will be limited and most of the power will be expended rotating the motor rather than accelerating the load. 


The information provided in Tech Tips is not meant to be all-encompassing, but rather to draw attention to and provide information about the particular subjects covered. All suggestions and recommendations contained in Tech Tips are based upon information that is believed to be accurate to the best of the experience and knowledge of PTDA’s contributing members, but are made without guarantee or representation as to results. PTDA and Tech Tip contributors expressly disclaim any warranties or guaranties, express or implied, as to the accuracy or completeness of any information published in Tech Tips, and disclaims and makes no warranty that the information in Tech Tips will fulfill any of your particular purposes or needs. PTDA and Tech Tip contributors disclaim liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on Tech Tips.