Re: Correct voltage

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "kdoney_63021"
<kdoney_63021@y...> wrote:

> Let me apologize up front since this is not exactly on topic but it
> is for a vacuum table on my CNC router, which will be activated by

a

> relay from my CAM system. :-|
>
> I have a vacuum pump, which specifies on the label:
>
> 220 volt 1.9 amp
> 240 volt 2.2 amp
>
> I have a transformer, which can give me 210, 230 or 250 volts. I

want

> the most torque since vacuum is more important to me than volume.

It

> seems from the label on the vacuum that allowable amperage

increases

> with voltage. This does not seem right to me since the allowable
> wattage would increase with voltage.
>
> Now the questions. Can I go to 250 on my transformer? Should I, if

I

> want the most torque? At what amperage do I fuse the circuit?

This is obviously a unit that is designed to run form the standard
mains voltage in the US. The "nominal" line voltage in most places
is 120VAC (240VAC across both legs). While there can be variations
in certain locations from 110VAC to 125VAC the average is 117 to 120
with cross phase running 220V to 240VAC. Your problem with running
your unit at 250 would be that if the primary voltage climbs you
could put too much voltage on the unit and cause the motor to
overheat. Do you not have access to both legs of the AC at the pump
location? You could save the use of a transformer at it's inherent
losses by running directly off the 240VAC and using a SS relay rated
for that amount. The computer can drive the SS relay.