Training: Interpreting Motor Spec Sheets presentation wanted

[kmcclary]

Originally posted by Ken L
[See: ] http://www.chiefdelphi.com/forums/pa...le&paperid=197

I have a feeling the first few pages are what you are looking for.

Thanks! That's MUCH closer to what I was searching for. However, I'm still looking for something even simpler. Maybe a one page "Glossary", and a one page chart with arrows and formulae on it, as a two sided "reference sheet". Is there anything like THAT already out there?

BTW, regarding the formula for actually PLOTTING the curves, based on the table data... The two lines of course are "straight" forward. But you say in the paper that the power curve should be "an inverted parabola". Aren't there a whole family of parabolic curves that fit three points?

What's the exact formula for that parabola, based on the known parameters, for plotting the arc perfectly? I'd like to set up a plot routine to actually DO the plots based on the table data, and need the full formula.

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Another motor question regarding stall measurements of an unknown motor (we plan to do this as an experiment): Can you "scale down" a stall measurement experiment for safety, and still get accurate data?

IOW, can we do this experiment with a smaller power supply, and simply multiply the torque and current measured to the full values based on the ratio of the "FULL" voltage vs "USED" voltage, or are there some resistance or force nonlinearities due to motor heating (or other thing) that messes up this technique?

If we CAN do that, it would allow stall parameters to be measured via a lightweight rig, made with a simple motor clamp, a vice grip on the shaft touching a postal scale, and an under 10A benchtop power supply. That would much safer for the students to do. (If forced to run it at full values, we'd have to set up 100A supplies, ammeters, scales, etc, and STRONG clamp setups to insure something doesn't come loose and hurt something or someone!)

So, will scaling everything down linearly still give valid stall data, or are motors really nonlinear?

Thanks!

- Keith