Re: Torque when using Micro Step or Full Step

Hans,

It's not that simple. This is a subject that has wheels within
wheels. That is what makes it so interesting to me.

We were discussing low speed motor behavior, i.e. where the drive is
limiting motor current. At high speeds the dynamic is entirely
different.

At high speeds what matters is motor inductance and power supply
voltage. High speed in your case with your motor and supply voltage
would be what happens above 10 revolutions per second.

The dominant factor then is voltage divided by the square root of the
motor inductance. That is what sets the maximum motor power output
and is independent of low speed behavior.

A 975 oz-in motor versus a 445 oz-in motor will certainly have higher
inductance. It will certainly have more torque at low speed but it
will have less power (speed times torque) at higher speeds.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Hans Wedemeyer <xyz@h...>
wrote:

> Mariss,
> Ok now I understand.... look for a 445 oz-in motor for sale on eBay

sometime soon.

> The next version of this motor has a holding torque of 975 oz-in

for the same drive current.

> As the current motor is marginal I'm hoping a 100% increase in rate

holding torque will solve the problem.

> What do yo think ?
> Best Regards
> Hans W
>
> "Mariss Freimanis " wrote:
>
> > Hans,
> >
> > You have missed the point and that is my fault. The moment a full-
> > step driven motor takes a step, it moves the motor at a high

velocity

> > to the next step location (1.8 degrees away). This velocity is

wasted

> > energy and must be accounted for.
> >
> > A microstepping drive parcels out the "distance to move" in much
> > smaller increments. Energy is mass times velocity squared divide

by

> > 2. If the distance to move is 1/10 as far, velocity will also be
> > 1/10, and the energy invested in momentum will be 1/100 compared

to a

> > full-step drive.
> >
> > The step rate doesn't matter if it is 5 steps per second or 1 step
> > per hour. The effect is the same.
> >
> > Mariss
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Hans Wedemeyer <xyz@h...>
> > wrote:
> > > Mariss,
> > > The motor is brand new special made (spindle lengths) and
> > guaranteed to be new because of that.
> > > The spec. sheet only talks about Holding Torque and it's +- 10%

so

> > the 445 oz-in motor may already only be a 400 oz-in !
> > > If Full step has an advantage at start up ( where my main

problem

> > is) If I used a control that allowed me to switch Full Step for
> > startup and micro step for normal running, that may be a solution.
> > > I'll consider that and see what I can come up with.
> > > In Series mode this motor require 2.8Amp drive and I may be

able to

> > throw together a L6203/L297 circuit and do the Full Step/Half Step
> > tomorrow.
> > >
> > > I'll post results.
> > > Best regards
> > > Hans W
> >
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