Re: Power Supply for Servo System (Hot Supply using Variac)

Bad bad bad Idea. The transformer is the only thing isolating you
from wall current. Radios in the 1920's were made the same way with a
bridge and resitive wire - when enough people died using them they
stopped production. Please don't build the "Shockmaster 2003" power
supply.

Doug

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "autom8_it" <engineer@s...>
wrote:

> I want to run my servos using 130VDC MAX and my plan was to build

the

> supply using toriodal transformers, bridge and big cap. This will
> work but a friend of my came up with something today that I can't
> think of a reason not to do but seems too simple to jump into.
>
> Remove the transformer and put the input to the bridge right to
> 120VAC line. First this would give too high of a voltage(approx
> 168VDC) so then he said use a variac(adjust 120VAC from 0 to
> 140VAC). I do have four 10Amp Variacs available but was wondering

if

> there is any thing I am overlooking in doing the supply this way.
>
> The only thing I thought of was no isolation but what is that

buying

> me?
>
> Should I buy the toroidal transformer or will this work just as

well?

>
> Any comments would be greatly appreciated.
>
> Thanks,
>
> John