Motion Analyzer Support

Current calculation change

We have improved the way Motion Analyzer calculates motor current. The impact of this change will vary by application but in some cases the motor thermal capacity will be less than it was before, at times dramatically. In addition, the power analysis results may vary slightly from what you had previously calculated.

A challenge in calculating the motor current is estimating the dynamics in the torque command resulting from the outer velocity and position control loops. Traditionally, many sizing applications ignore this added complexity and simply assume a drive with infinite bandwidth. This however can result in an understating of the current and consequentially the thermal behavior of the motor, resulting in systems that look good on paper but have issues in the field.

To address this risk, there has been accommodation for torque dynamics in the online version of Motion Analyzer since its first day. We have now made improvements to the algorithm that represent the real world system even better than before based on further testing and refinement. While the change is small, even small changes to the current calculation can have big impacts on the thermal behavior of the motor so effects may vary. The biggest impact will be seen on large axes with low inertia ratios.

Feel free to email us at motionanalyzersupport@ra.rockwell.com if you have any questions.