Re: Power supply for servos

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

>
>
> andrebarclay wrote:
>
> >Hello All,
> >
> >Does anyone have any guidelines on sizing a power supply for 3

75V

> >10A servo motors?
> >
> >
> This is for use with Gecko 320 or 340 drives? In general, these

drives act

> like switching power supplies, so except in the condition where

they are

> accelerating hard near full speed, the current into the drive is

much less

> than the current out (at the same time, the voltage in is higher

than

> voltage
> out). Bulk unregulated DC supplies usually can tolerate short

duration

> current surges over the transformer rating (this happens every

time you

> turn it on, for instance). So, you don't need a power supply that

can

> deliver
> a continuous 30 A. If this is for a CNC router, you may use more

speed than

> on a milling machine, for example, and a 15 A supply might be a

good

> goal. For a mill, even a 10 A supply will probably work, if enough
> capacitors are there to hold charge. For heavy industrial use, a

25 %

> in capacity from above would be a good idea.
>
> Now, these numbers are based on transformers rated for capacitor-

input

> rectifier use. If the transformers are rated for RMS current

only, you need

> to up the ratings by 25% or so, again, as the current peaks in
> capacitor-rectifier
> service cause more heating than for a resistive load. Unless you

buy

> transformers
> new from Stancor, Thordarson or other brand name, it is often hard

to

> know what
> the current ratings are based on. "Control Transformers" are

generally RMS

> rated, as would be a "Step-Down Transformer".
>
> Jon

Thanks Jon. That helps me a great deal.

Andre