Re: stepper torque.....please help

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:

> Kayla Sanders wrote:
>
> > i wanted to ask you all something .....i have 3- 305 oz-in motors
> > @4.5A per phase and 2Vdc ,using a 28 Vdc/12 A power supply,direct
> > drive config.. i was thinking about going with an "FET-3" 3 axis
> > unipolar controller rated up to 15A per phase with proper cooling
> > from stepperworld.com (only 135$ compared to gecko's at 114$

each)

> > (are the FET-3's any good?).....being that the rated torque of

the

> > motors are for bipolar parallel, what would the approximate

torque

> > drop be when hooking them up to a unipolar controller in

parallel??

> > and is it going to hurt these motors using this power supply at

this

> > amperage? the capacitors that i choose will reduce the current to
> > the motors?? or the voltage?? or both???
>
> First, if these are 4-wire motors, they can't be used with a

unipolar driver.

> You need 6- or 8-wire motors to make the right connections.
>
> You mention a unipolar driver in parallel. That doesn't make

sense.

> With 8-wire motors, you can select either parallel or series

connection

> for a bipolar drive, but you can only connect the motor one way for
> unipolar.
>
> The holding torque will be about the same, assuming the motors can
> be used on a unipolar drive. The real difference is when the

motors

> are moving. Many unipolar drives don't drain the current from the
> winding that has just shut off very quickly, so the rise of the

current in the

> opposing winding rises slowly. R/L drivers are the worst in this

regard,

> and you should avoid these like the plague. Anyway, in general,
> a bipolar driver will perform better than a unipolar. And, a

chopping-type

> drive will always perform better than an R/L driver.
>
> An overrated power supply will NEVER hurt the motor, as the driver

is

> responsible for limiting the current. The capacitors in the DC

power

> supply STABILIZE the supply voltage. They do not alter the current
> or voltage.
>
> Jon

ok well how about this then........i have just bought 3 Vexta 305 oz-
in 2 phase steppers@4.5A 2 phase excitation,2Vdc.,8 wire and am
trying to determine what kind of driver i can get that is not too
expensive(ie.gecko's)
xylotex.com has a 3axis ,2.5A bipolar driver . my question is can i
use this driver to run these motors with a 24Vdc/12A power supply if
i run them in series?if so , do i need to use some kind of resister
for current limiting? and what (approx.)i know that running steppers
in parallel is better, but i cant use this driver if i run them so.
what would the torque then be with these motors in series in this
setup with the xylotex driver?
i ve also been looking at an up to 15A, 3 axis unipolar driver from
stepperworld.com that would definately have no problems running my
motors, but i read that using a unipolar driver is a bad idea
considering the lower performance of it compared to bipolar drivers.
is this true??what would the actual performance(estimated)be if i
used this stepperworld driver compared to the other xylotex driver?

i want the best performance i can get without spending more than the
whole grizzly minimill cost to begin with. which direction should i
go?? ive asked the same questions in the mini mill group but i have
yet to recieve a clear and concise answer or suggestion(not that i
can understand anyway
any help would be great..thanks