Hey, hey, hey... I remember this discussion thread! Just got the Mod. Notification today (wonder what happened to the notifications for the December posts, plus Iwire's last post?)
Anyhow, I'll address the replies in order (not too much to address, as Bjarney has done an excellent job already!).
*To Bob ("Iwire"):There are a few pictures of the Locomotive's Operation Control Stand, but not any of the Relay Logic based Control Equipment.
There's an "On The List To Be Scrapped" SD45 T-2 which would make a great "Model" to get Control Equipment and Prime Mover pictures from. It's near me at a Scrap Yard.
Will let you know whazzup with these pics!
Dnkldorf:
I noticed in the schematics for the grounded conductor, there is no fuse. I assume it is the same theory on fusing the nuetral in a 4 wire system, it is the return back to the source and you never fuse the grounded conductor. Hope I am on the right track here.
Now comes the Question.
Why then do I see a corner grounded 3 wire system coming into a MDP which is OCPD is breakered. 1600A. Then it leaves as a branch circuit breakered and feeds a 400A bus duct. The bus ducts themselves have fused disconnects feeding machines that have fuses in them? All 3 phases fused.
Isn't this fusing of the GC a hazzard?
Note: system is 240V Bphase grounded.
Bjarney covered this one well. Only thing I could add would be the "Disconnection Of All Ungrouded Conductors + The Grounded Conductor Simultainiously" thingee - as regarding a Circuit Breaker + EXO Disconnect Switch.
One more while I'm thinking about this.
I have a plant that maintains its own substation. 34000-4160VAC.
The 4160 feeds a 3w 480V CG delta in the rear of the plant. It has a seperate feed of 4160 feeding "pod" SP transformers 208V on the side of the building. 208 3ph 4 w.
Now then, in theory the grounded conductor of the 480 is electrically the same point as the "nuetral" on the 208 side.
Any schematics of this around? I still have a hard time figuring out why the 480 doesn't "bleed" into the nuetral of the 208 side.
The 480 VAC 3Ø 3 Wire Corner Grounded Delta is one SDS (Separately Derived System), and the 208Y/120 VAC 3Ø 4 Wire is another SDS... is this correct?
They are both Isolated from each other (so to say...) and there is only one connection to each system - and both are driven to "Earth-Ground" Potential.
There will still be a measurable Voltage between the two systems, and with this, a measurable level of Current will flow between them also.
The Voltage level between the two systems will fall well below 208 Volts - more like no higher than 25 Volts at the farthest points.
There should be some Schematics around, which cover these setups. If not, let me know so one can be generated.
*BTW: If the Transformer's Primary is a Grounded Delta with a Wye Secondary, that one would be an odd-ball setup and definitely not in the list of Transformer Drawings posted on-line here!
Let me know if you have this setup, and I will discuss the oddity with the "Elders" for reasons of "Whaddaheck!!!"
Joey D:
I happened to run into this type of 3 phase 240volt service today. I still don't understand the theory behind it but will chew on it till I do.
While I am learning, is any 3 phase 3 wire motor load OK to run on this system? Should this panel be used only for 3 phase loads? The panel I ran into today has a 2 pole 20 in it feeding a forced hot air furnace.
As Bjarney has mentioned, 240 VAC 1Ø 2 Wire loads and 240 VAC 3Ø 3 Wire Loads - Motor Loads, are applicable on this System.
Just don't expect to use any 120 VAC Loads on this System directly, without letting out smoke!
Scott35