http://www.tristateindustrialgroup.com/sites/tristate/uploads/documents/Transformers.pdf

wuz given the above in a continued effort to dislodge my cranim from my large intestine

of note is pg 14 >>>>>>>>> Y Y Closed / Neutral Prim Yes Sec Yes , which is what i believe i've been trying to describe. The following from it>



YY Closed / Neutral Prim yes Sec-yes



The Primary Nuetral should be tied firmly to the system nuetral, otherwise exessive voltage may develop on the secondary side

If 3ph load is unbalanced, part of the load current flows in the primary neutral

The 3rd harmonic componet of the Xformer exciting current also flows in the primary neutral

For these reasons, it is necessary that the neutrals be tied together as shown

If this tie were omitted, the line to neutral voltages on the secondary would be very unstable

That is, if the load on one phase were heavier than on the other two, phases would rise

Also, large 3rd harmonic voltages would appear bettween lines and neutral, both in the xfomer, and in the secondary system, in addition to the 60HZ component of voltage.

This means that for a given value of RMS voltage, the peak voltage would be much higher than that for a pure 60Hz voltage

This overstreeses the insulation both in the Xformer and in all apparatus connected to the secondaries

Last edited by sparky; 09/07/11 09:54 PM.