Re: stepper driver-transformer sizing question

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Scott Riddle"
<sariddle@l...> wrote:

> I am a little confused on sizing a transformer to drive some small

30-

> Oz-in bi-polar steppers. They are rated at 3 amps/phase 2.1Vdc and
> the IMS IB462 drivers I have are good for 12-40V 0-2Amps 160Watts.
> What I am thinking is that the motors can take 6 amps (3 per

phase).

> But can the motors only take 12.6 watts (6A x 2.1Vdc).

Actually, the motor only needs 3 amps max at any time, so don't go too
for off looking for gigantic power supplies.

One winding is powerered while the other is not, or one is partially
powered, while the other is also partially powered, but the driver
does not power both coils at full amps at a steady state.

> I would like
> to just buy 1 transformer to supply power to 2 or 3 steppers. I am
> not looking for high speed mainly low speed high torque.

Good, because steppers are pretty much constant power. the faster
they spin, the weaker they seem. For more data , check out the white
papers at www.geckodrive.com. Read each one seperatly first, before
you download the whole she-bang.

Wire them as SERIES if you can, that would be 2 coils in series for 6
or 8 wire motors. That will reduce the total amperage by half,
reduce motor heating AND get full use of the motor/driver combination
you have.

> Can someone help me on sizing the transformer required?

For a chopper driver, size for 2/3 of the Total amps of all motors.
Chopper drivers are very efficient and are not on all the time. 2/3
of the total is fine.

> Would I also need to run
> resistors on series with each driver
> to limit the current each driver
> would be able to recieve?

Only if you are using a unipolar driver, or a very simple circuit.
Or, if the driver manufacturer expressly describes the need, in which
case, seek out another driver.

For the driver you have, you will need to make sure you set the
current output so it delivers the maximum. If your motors are rated
for more than the driver.

>
> Thanks
> Scott Riddle