Re: Power Supply for 4-axis CNC stepper driver

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Dammeyer <johnd@a...> wrote:

> Hi Dave,
>
> Eventually the transformer will smoke. Before my large transformer

arrived

> I was playing around with a 24V 1A DC supply; note 24VA. Two Size

23 1A

> steppers. With both running the voltage would drop to 18V and the

box got

> really warm. Just think if I tried to use that 24VA supply for a

couple of

> Size 34 motors and a driver that tried to supply 6A per phase.

Magic smoke

> time.
>
> Now failure on stepper conversions can happen for a lot of reasons.

If you

> full step, both coils are on so you need 100% of the motor nameplate

current

> to provide full torque.

I thought that for full step, you needed 100% one each phase ? that
would be 200% of nameplate.

> Remember Amps x Turns is what creates the torque.
> Go and have a coffee and come back and the motors will be hot.
> Micro-steppers never apply full current to both windings

_at_the_same_time_.

> The most you get is 70% at the same time. In fact because the

windings are

> rated to dissipate heat you could get away with running higher current
> through the windings if you micro-step.
>
> BTW, the only way to measure current on stepper systems is with a

scope.

> Don't bother using a DVM.
>
> John Dammeyer

I'm heading out for the weekend but I wanted to figure out how to ask
this properly. I'm in a rush, so, I'll mumble....

the scope would show instantiansous responses, but the filter cap
would alevate or attenuate most of that from reaching the transformer.

even without a scope, I would expect to see some noticable changes
with a DVM if the power supply was only 10% of the proper rating.

Dave