In the last post, I gave an overview of what thermal metrics are relevant to motor drive applications and how they drive the important performance metrics of controllers and motors. In this post, I’m going to look at how to measure those thermal parameters empirically in at least a crude way, but with enough accuracy to be useful for practical design applications.

What do we want to measure?

There are a set of parameters that we would like to be able to measure that have some overlap between the controller and motor case. For both, we want to be able to measure:

One of the things I’ve been wanting to understand better for quite a long time is the thermal performance of moteus and motors when used in realistic applications. In many, if not most systems, thermal limits of one or another determine the eventual sizing of controllers and motors and are one of the most important performance factors. I’ve covered this before to a superficial degree in a previous post (customizable pwm rate) but it was far from a general solution. The newly provisioned dynamometer fixture, with its ability to accurately measure input current and power, provided a great opportunity for finally tackling this. This post will describe a bit of the motivation for the work and why you should care.

This post will be short and sweet. https://mjbots.com now stocks mating solder cup MR30 and MR60 connectors:

• MR30 store links: Female / Male
• MR60 store links: Female / Male

As their name implies, MR30 are good for 30A peak (15A continous) and MR60 are rated for 60A peak (30A continuous). They have their own built in strain relief attachment, so no heatshrink is necessary during cable construction. Since moteus controllers have no connectors for motor phase wires, these can be used inline if you need to frequently disconnect and reconnect motors. We use them all the time here and figured that you might as well!

Long ago, in a workshop not so far away, I built a dynamometer for characterizing moteus controllers and motors. In the intervening 5 years, we released the moteus-r4.11, moteus-n1, moteus-c1, and now the moteus-x1! For each of these controllers, and the many firmware releases in between, this fixture has still served as a critical part of the validation procedure for new firmware releases and new product releases. However, it was time for a few improvements when tackling the moteus-x1, so here is a brief write up of the new result.