Team Lazy Gecko

Some pictures of various internals of BOMA/BOMA clones.

Manufacturer data is at https://www.uumotor.com/uuen/wp-content ... ngdata.pdf. They chose really weird numbers to provide though, and they don't make a whole lot of sense. It's also really hard to make sense of them without definitive info about what the throttle input to the motor controller is doing, even ignoring the way they don't say which controller they're using.

https://drive.google.com/file/d/1fmC6hs ... sp=sharing is some other data (from http://build-its.blogspot.com/p/motor-c ... ation.html). This data makes way more sense, and is also presented in much more useful and well-explained ways.

Anybody know how many pole pairs this is? Both of the sets of reference numbers seem to skip over that...

Aren says 3 pole pairs for something he got that's not quite a BOMA. I'm curious to see the shape of the flux linkage and resistance for various motors, along with identifying markings to tell them apart. I'll post data for what I've got access to next week, and would be interested in seeing stuff from other people.

Interesting data for a motor:

• Resistance. Measuring this directly is annoying because the numbers are so small contact resistance gets in the way. I think the easiest way to collect good data is hooking up two phases across a current-limited power supply and leaving the third phase floating, then measuring the voltage (either with the supply if you trust it, or a multimeter). Putting 15A through it should be enough to get pretty solid data.
• Flux linkage shape. This is the shape of the back EMF waveform, among other things (what makes a motor sinusoidal or trapezoidal or something else). Basically, attach an oscilloscope across two phases (leave the third floating) and spin it with a drill at the fastest speed you can. Grab some data and describe the function. If it's not something simple like "sin wave, 3V peak-to-peak at 300RPM" then a picture of the scope screen (with divisions visible and scale recorded) works nicely.
• Pictures! Take pictures of the motor so we can tell what it is, and if it's the same as another motor. Links you bought it from help too.
• Self-inductance of each phase. This is really hard to measure without custom code on a motor controller, so probably not going to get this.

I collected data on two of these motors. It should all be fairly precise, but no promises. They're both basically identical on outside dimensions. Second motor is coming in a second post, because apparently I have too many pictures for one post...
1600W BOMA
This is what the nameplate looks like: Views from the outside: Views inside it: The rotor: The stator iron is 67mm long, and the rotor magnets are 71mm long. The OD of the rotor is 49mm.

The line-to-line flux linkage is 0.033826 * cos(theta) + 0.003439 * cos(7 * theta + 1.570796) V/(rad/s) aka N*m/A. Plot of that: Resistance: 0.638V / 3.77A = 0.17ohms * 1.5 = 0.25ohms overall.

The code I used for analyzing the data, along with the data itself, is at bsilver8192/motor-analysis.

And here's data for the other motor which Aren bought.
1800W MY 1020
This is what the nameplate looks like: Views from the outside: Views inside it: The rotor: The stator iron is 77mm long, and the rotor magnets are 81mm long. The OD of the rotor magnets is 49mm, and outside of the bands holding them on is 49.6mm.

This motor also has a moderately strong 7th harmonic in the flux linkage. The line-to-line flux linkage is 0.032025 * cos(theta) + 0.002429 * cos(7 * theta + 1.047198) aka N*m/A. Plot of that: Resistance: 0.650V / 3.77A = 0.17ohms * 1.5 = 0.26ohms overall.

The code I used for analyzing the data, along with the data itself, is at bsilver8192/motor-analysis.

This is awesome. I am working on getting access to a scope, and I will have both an 1800w BOMA, as well as the steel UU motor to add to the collection. I will try to get the same data as you, but I am pretty much just learning how to use a scope, and your process, so I might have questions.

Turnigy Aquastar T20
Dug up data from the T20 too. All my data is with it in Y (slower) configuration. https://hobbyking.com/en_us/turnigy-aqu ... tore=en_us is the canonical location for finding it.

From the outside, with water cooling jacket: With the jacket pulled off: The rotor: The tan stuff is some kind of fiber (fiberglass? kevlar?) wrapping the magnets to hold them together.

The motor has a fairly strong 5th harmonic in the flux linkage. The line-to-line flux linkage is 0.006595 * cos(theta) + 0.000970 * cos(5 * theta + -1.570796) V/(rad/s) aka N*m/A. Plot of that: Per-phase resistance is ~0.0079 ohms.

The code I used for analyzing the data, along with the data itself, is now at bsilver8192/motor-analysis. I'm also going to update mistakes in some of the data for the other motors right now.

So the T20 looks smoother than the other motors? What can this data tell us about the characteristic differences between these two motors?