Re: [CAD_CAM_EDM_DRO] Power supply for servos

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