*** New Tool - Data Plotter

[Mathurin]

Wow, fell on this accidentally while frocking around with google on endless-sphere.com, hunting for browse able directories and other goodies, and then I searched for .xls files.


So I, managed to get the Works 2.0 version to show up reasonably well.
Saved it in some version of ms Excel so it ought to work.



How did you figure respective motor's resistances?

I guesstimated for the P2-A based on printing out the motor curve and extending the A curve till it reaches stall, gives ~90A at 36V, 3240w. Plugging in P=V^2/R gives 0.4 ohmz


Going a bit further:

36V P2-A
No-load speed: 3360Rpm(351.9 rad/s)
Rated RPM: ?
Rated current: ?A

K = 36.0 / 351.9 = .102
back-emf at 3000rpm = .102 * ? = ?
Winding resistance = (36.0 - ?) / ? = 0.4ohms
heat dissipation at rated load = (? * ?) * 0.4 = ?


Plugging in 16A as rated current yeilds this:

36V P2-A
No-load speed: 3360rpm(351.9 rad/s)
Rated RPM: 2771rpm
Rated current: 16A

K = 36.0 / 351.9 = .102
back-emf at 3000rpm = .102 * 290.2 = 29.6V
Winding resistance = (36.0 - 29.6) / 16 = 0.4ohms
heat dissipation at rated load = (16 * 16) * 0.4 = 102.4

Does not match the graph on Brett's site, it shows 180w worth of heat @ 16A/~277rpm

 

[monster]

safe your graphs suc

none of the axis are labeled and you have missed out the X axis altogether.

 

[lawsonuw]

safe your graphs suc

none of the axis are labeled and you have missed out the X axis altogether.

aw, cut him some slack. HE knows what everything means, what's he need to add labels for.

(sorry just had to pile on too, Safe)
Marty

P.S. that looks like a rather useful spreadsheet when dealing with surplus motors.

 

[safe]

This thread was about the "Data Plotter" spreadsheet. There's a few graphs involved in unrelated discussions that I'd rather not get into. The main thing was that the "Data Plotter" can take raw data about a motor and make some estimation of it's resistance value. It's not intended to be exact, but it seems to do a fairly good job because I've randomly guessed at resistance values and arrived at the same place using my "runtime" spreadsheets. It's a nifty tool once you actually download it and place real data (like from Unite or PMG 132) into it and see that everything lines up as expected.

The goal is to align the "dots" of data with the "curve"... so it's a "data fitting" program to discover parameters that the manufacturers sometimes fail to mention.

Resistance is the number one MOST important value to know about your motor because it really defines everything about it's heat creation. Without knowledge of resistance you really can't do anything in calculating the way a motor is going to behave under stress.