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

autom8_it 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?
>
>

Well, if anything shorts out, you could be dead! An insulation breakdown
in the motors will cause a lot of fireworks. A breakdown in the servo amp
could convert your entire computer into a smoking pile of debris. (I've
seen
what 24 V DC did to a computer some years ago, it was NOT a pretty sight!)

Are you absolutely sure your servo amps have full galvanic isolation between
the control circuits and the motor circuits?

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

I wouldn't even think of doing this without isolation, with whatever
transformer
is available.

Jon