Re: [CAD_CAM_EDM_DRO] Re: How many kva for a control transformer...?

Lance Hopper wrote:

>Hey,
> Yes I know, but this machine will actually be in an industrial
>environment. My goal is to have only the 220 3ph coming into the
>machine as power. Therefore, all lower voltages will be derived from
>the 220 3ph input power.
>
>
> I've got 2x 1 kva transformers with 120 secondaries, and then I've
>got a single 2 kva with 120 secondary.
>
> I've got 2 separate NEMA 3R enclosures. My plan is to mount all
>the 3ph in one and 1ph in the other. These will be physically
>separated on the machine, about a 5 ft separation.
>
> 1)... Being that the VFD is the big noise maker, should I mount the
>control transformer(s) in the 3ph box with the VFD and run the 120
>1ph across to the 1ph enclosure?. Or should I run the 3ph across to
>the 1ph enclosure and mount the control transformer(s) in the 1ph box?
>
>

Ugh. I'm not sure it makes much difference. I had to put a line filter
unit
at the power input to my VFD, or it caused some problems with other
equipment. The computer and CNC was fine, but the video monitor power
cord ran near the VFD wires, and that got "fuzz" on the screen.

If you have all the computer and auxilliary stuff in one enclosure, then
maybe
get a good power filter strip and use that as the 120 V source in that box.
That should solve your worries.

>
>Also note, there will be 120 back to the 3ph box for the contactor
>coils.
>
>2)... Then there is the Digispeed, PWM to analog converter, which is
>used to control the VFD. Somehow these low voltage control wires
>will have to cross the ~5ft span to the 3ph box. Which would be more
>noise tolerant, the PWM side or the analog output side? (IE should
>the Digispeed be mounted in the 1ph box with the breakout boards or
>in the 3ph box with the VFD it will control?)
>
>

Probably the analog output should be run to the VFD. It is already well
filtered for its own noise.

>
>

Jon