Re: Transformer question - ground ?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude" <

>
> I have three 1 amp (166 oz-in, NEMA-23 dbl stack) motors on a
> mini-mill. I'll probably swap them out for some 250 or 300 oz-in once
> I get the machine running. (AutomationDirect has 266 oz-in for $40/ea
> 3A each)
>
> Each of these transformers is about as large as the 10A one I got from
> MPJA (110v pri and 24V sec) so I assume it should handle about 6 amps.
> Using Mariss's 60% rule for amps, means that 3 motors running at 3
> amps each should require a power supply of 6 amps.
>
>
> The drivers are Gecko 201a's so there is no problem with over voltage.
> The bridge is rated for 200 V 10A and the caps are 100V rated.
>
> Since I have a few of these transformers laying around, I figured I'd
> use them.
>
> Testing shows that this grey wire is infinity to everything else. the
> case, the black and white input, the two pairs of outputs.
>
> with 110VAC on the black and white, the pairs have 8 volts and 28
> volts with no load and there is zero voltage between any of the
> secondary wires and the grey wire.
>
> Maybe is is just a spare wire used to hang the unit when it was dipped
> or some off thing ?
>
> Makes me feel that just tyeing it off would be best.
>
> Dave
>

Transfomer mfgs don't put in extra wires (too much labor) even to hold
stuff by. It's probabaly tied to an "Electostatic Sheild". A layer
of copper foil around the outside of the regular coils (or in some
cases between the primary and secondary windings). It acts as a high
frequency short to RF type noise and acts to cancel interwinding
capacitance (which passes HF signals through the windings. You can
leave it unconnected or ground it to earth (chassis ground). It
probably won't make any difference at the frequences in this case.