While testing moteus controllers, it is often necessary to experiment with high power conditions. For short durations, any decent sized brushless motor can work, as the windings have a non-zero thermal mass and take a little bit to warm up. However, when testing at high power for extended duration, it can be hard to find a way to get rid of all output energy. Even blowing a fan directly onto a motor only gets you so far when you are trying to get rid of 1kW.
Thus enter my resistive dummy load:
This is just a block of DC water heaters screwed into a plastic container. They are wired in series with some high current inductors to roughly approximate the inductance and resistance of a motor in the range of what is normally driven by moteus. When conducting a test, the container can be filled with water to greatly increase the available thermal mass (and if need be boil away the water).
Parts and Assembly
I have used this fixture with two different elements, a 24V 900W one, and a 12V 600W one depending upon what resistance I want to test with:
The container is just a basic polyproplene plastic one, so that it should be safe up to at least the boiling point of water:
The inductors are 33uH, 30A:
To assemble, I used a 1.25″ hole saw to cut each of the holes, then used a 1″ NPT nut to fasten each element in place. Each phase connected to 3 of the inductors in parallel in series with 4 of the heating elements. All three phases were tied together in the center to form a wye topology.
A Modicum of Fun 