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  1. #11
    Quote Originally Posted by irving2008 View Post
    Hmmmm hadn't though about that. Should be powering both windings in parallel then?
    If we're just using it as a load, since it doesn't look like we can get useful information from the other phase, then yes I tend to agree. Also you wouldn't get rated power with just one phase energized.

    Quote Originally Posted by irving2008 View Post
    Maybe, but a dropping weight and pulley is easy to calibrate
    Yep, could even use dropping a weight to calibrate the other system.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  2. #12
    It's great seeing you two "talking dirty" with one another again

  3. #13
    Quote Originally Posted by Jonathan View Post
    Just spotted something interesting...

    I measured the back-emf voltage from the 3.1Nm stepper motor at 1200rpm and it's 66 volts, so using those numbers k=0.525 Vs/rad. The unit Vs/rad is dimensionally equivalent to Nm/A ... i.e the 'torque constant' of the motor, so we can use this to find the torque for a given phase current. Rated phase current is 4.2A, so for both phases T=2^0.5*4.2*0.525=3.12Nm. That matches the holding torque specification rather nicely, so maybe this could be a simple way to find the rated torque of stepper motors. Or more usefully, use the formula for phase current (something like i(t)=V/R-(V/R-I)*e^(-t/(L/R))) multiply by k to get torque as a function of time then integrate to get the mean torque and then the torque vs speed curve for the motor. I think this should be more accurate than the usual approximation.
    Yea i would have to agree with what he said....because i don't have a clue....what he just said....

    Quote Originally Posted by WandrinAndy View Post
    It's great seeing you two "talking dirty" with one another again
    Agreed, all we need now is the shaft size equations to come into it...


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