Transformer

[Tom749 0]

What is the main purpose of the earth point at the attached picture? (1) / (2) / (3) What is the meaning of the number (4) ? What is the main feature of the lighting transformer? Thanks for your help in advance. Edited 19 Sep 2011 by Tom749

[nehpets 19]

What Picture?? There's no attachment. Steve

[OkiePC 14]

1) the transformer iron core is grounded 2) the transformer secondary neutral is grounded 3) the transformer secondary is grounded again from wire 2 (not good but there's a numerical reference that may explain) 4) 3000va this is the power rating of the transformer 3000va or 3kva divide that by volts to get the current in amps Edited 8 Nov 2011 by OkiePC

[Shiner 2]

Yes, the third ground is questionable. I would like to see what note is referenced by the drawing. By having a grounded leg on X2, you have a grounded conductor, meaning that it carries current, but the voltage is referenced to ground. Some would say the voltage is pulled down to ground. All the current that is in the field is supposed to return on this path. If you have a second point of ground reference on the same conductor, you have the possibility of having the earth, or whatever you have derived your ground from (building steel, framework, piping) carry current. This is a hazardous condition!!

[OkiePC 14]

I agree about the safety aspect. I was hoping the OP would go find that his full paper notes show a comment that says something to the effect of "T1 ground wire may be physically connected in either location shown". But if I had to wager I bet it was just an oversight on the part of the designer (one too many paste operations) and that there is only one ground tied to neutral on the real machine, and only one intended on paper.