Re: Transformer sizing?

Hello JV,
I can explain a bit on this subject and I'm sure others can
explain more. A good book on the basics of electrical principles for
the sake of reference is a big plus too.
Not to sound flipant but, there is a lot of stuff between the
transformer and the stepper motor that can be even more confusing.

To be helpful,
Transformers are rated in VA which is the same as Watts(Volts *
Amps).
Average draw means just that. Add up all of the loads in like
terms, calculate an average duty factor for each. Same for the peak
and add 25-30% just to stay safe.
The 67% you mention is an upper limit to the intended max load you
plan on having it drive. Let's say you you have a 10 va(Watts)
transformer on hand. Your max load would be 6.7 Watts. This way it
will last longer and never be loaded to it's limit, preventing
damaging heat build up taking into consideration the peak beyond the
67% at whatever duration. It is a minor cush factor. Circuit
protection will also be in the upper part of this region. No sense in
being too foolish.
It can be a balancing act when it comes to over/under rating. I
would relate this as to how tightly the smoke in them is wrapped.
Go to the big side of reasonable if funds permit.

DC

--- In CAD_CAM_EDM_DRO@y..., "jvbsa" <s8in@g...> wrote:
> Hi, I am just beginning my journey into CNC and would like some
info
> or links regarding transformers sizing for stepper motors (constant
> current supply).
>
> I am confused regarding the real operating VA requirement for
> transformers, Average current draw and peak, etc.
>
> I have seen the figure of 67% mentioned. Is this for one winding or
> for both.
>
> Kindly point me in the right direction.
>
> Many thanks
>
> JV