Hiya folks, I hope everyone had a good first week of robot build. We’ve written a detailed motor performance analysis document that highlights a few things.
First, we have updated performance curves and figures for the Kraken x60 alongside testing of other motors. Additionally, this document gives an insight on our testing procedures to keep things open with the community on how we gather our data.
The link is below, but also available on the Kraken x60 product page.
Thanks for posting! Could you provide free speeds measured for each motor? I can see it vaguely in the motor curves but on an axis with a max value of ~7000 its a bit hard to get a more precise number.
Repeat sampling at chosen intervals until load exceeds 1Nm (for FRC size motors this usually terminates around 65 Amps).
Were all tests terminated at 1Nm? If so, how was data past 1Nm obtained?
can we get current vs torque graphs please? very hard to see realistic current draws on the motor curve graph and only having one discrete point @ 40 amps is only a little bit better.
The table provides stall current and torque, with my limited knowledge I think that’s enough?
Torque is directly proportional to current. kT * current = Torque.
Note that kV and kT are inversely proportional, and kV*kT is theoretically the same for all motors. Always gear your motors correctly to exchange kV and kT at the output.
thanks
What is the maximum current output of the Talon FX?
Thanks for this report! It’s really exciting to have the performance characteristics of these motors measured across the same test equipment and test methods, especially since there appears to be no ASTM-style standard for such testing.
Does “For motor solutions that lack the FOC feature, three trials are sufficient” mean that three trials were performed per non-FOC motor tested?
Motor 1 - Test Run 1
Motor 1 - Test Run 2
Motor 1 - Test Run 3
Motor 2 - Test Run 1
Motor 2 - Test Run 2
Motor 2 - Test Run 3
Or does it mean that only three trials of non-FOC motors were performed total?
Motor 1 - Test Run 1
Motor 1 - Test Run 2
Motor 1 - Test Run 3
Thanks!
@daltzsmith I am also interested in the answer to this question:
The report says as much, and, if we’re interpreting this accurately, it means that only a small region of the Motor Curves displayed are actually measurement data; the remainder are extrapolated. Showing the full curves implies that the motors put out these numbers during testing.
For example, for the first two motor results, the green rectangle encloses the region where torque is under 1Nm:
For Kraken FOC, it’s a very small region, compared to what is shown, to the point that it’s difficult to resolve:
(also…what’s up with the gridlines and the right-hand vertical scale?)
Would it be possible for you to report the max measured values independent of the max extrapolated values? I realize that the “power at 40A” figure falls into that region, but it is the only one that does.
Alternatively, is anyone with a dyno interested in performing testing over the full speed range, but with input current limits, typical of the limits common in modern FRC?
I’m working on a flywheel dyno, but I’m not convinced I know what I’m doing enough to get half-decent data. If the data makes any sense at all I’ll post it, but I dunno when that’ll be (this tends to be a busy part of the year).
The most important value to measure, in my opinion, is how much and how long power can be sustained. 200A is pretty high for peak power output, to say nothing of a whopping 400A stall.
Edit: see below for the REV stuff; this is CTRE.
According to their manufacturer, at 80A (200%), the 40A Snap Action breakers will give you between 1.5 and 3.9 seconds before tripping:
At 200A (500%), you get 0.2-0.3 seconds before they trip , so the tests at that power level don’t need to be super long anyway.
The REV breakers are rated for 5-60 seconds and 0.4-2 3 seconds, respectively. Way longer than the Snap Action.
The rating for the REV 40A breaker is 0.4-3s to 500%
So there’s 2 different relevant tests as I see it:
With those two tests it becomes possible to compare the actual performance of motors on a drivetrain, or even to create a first order thermal model.
I think 80A per motor is interesting as well
@daltzsmith Any ideas as to why the Vortex measured markedly lower on efficiency than the other motors? At high RPM it clearly stands out from the rest, and this is in the high RPM region that actually had data collected without any extrapolating.
