LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Oh, I dunno. The timing just seemed right. :roll:
Adding a neutral to a 240 v delta transformer
- Thread starter voltairzap
- Start date
- Status
ty
Senior Member
- Location
- 3rd Rock from the Sun
I would like to copy Roger as well.
And I'd like to have him sitting next to me at my next exam :0
And I'd like to have him sitting next to me at my next exam :0
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
ty
Senior Member
- Location
- 3rd Rock from the Sun
Should we presume you mean your next electrical exam?
Yeah. not my next physical exam
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Roger,
In my post, I think I should have said 'I believe, as was mentioned by others above, I believe that you (the OP) would be better off with two separate transformers....'
I was trying to follow up on the OP's concept of using the delta:delta transformer and then using an additional transformer to derive a mid point neutral. It was only after I realized that the OP wanted to serve _3_ phase loads at 240V, and given the size of the loads, that I abandoned that approach.
Augie47,
A 'zig-zag' transformer can be used to derive a three phase neutral on a delta system. The OP wanted to do something analogous, and use some sort of transformer to derive a single phase center tap on one of the delta legs. A simple 120/240V autotransformer would do the job, if large enough, and if the delta transformer was large enough to supply the combined loads.
-Jon
In my post, I think I should have said 'I believe, as was mentioned by others above, I believe that you (the OP) would be better off with two separate transformers....'
I was trying to follow up on the OP's concept of using the delta:delta transformer and then using an additional transformer to derive a mid point neutral. It was only after I realized that the OP wanted to serve _3_ phase loads at 240V, and given the size of the loads, that I abandoned that approach.
Augie47,
A 'zig-zag' transformer can be used to derive a three phase neutral on a delta system. The OP wanted to do something analogous, and use some sort of transformer to derive a single phase center tap on one of the delta legs. A simple 120/240V autotransformer would do the job, if large enough, and if the delta transformer was large enough to supply the combined loads.
-Jon
glene77is
Senior Member
- Location
- Memphis, TN
Winnie,
Is the "Zig_Zag transformer"
Similiar to
the "simple autotransformer" you mentioned?
In my mind, the "simple" one seems to a component of the "Zig" model.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
A 'zig-zag' transformer is a 3 phase transformer with 6 coils on 3 legs. All coils have the same turn count. Somewhat more complex than a simple single phase autotransformer.
See http://www.electrical-contractor.net/forums/ubbthreads.php/ubb/showflat/Number/148726/page/2
One thing to add: I've seen diagrams where these are constructed using a bank of single standard phase transformers, which are often constructed as 480/240:240/120V devices. Since a zig-zag transformer needs to have the same number of turns, the HV side is wired parallel and the LV side wired series to make a 240V:240V transformer. This series/parallel connection just adds extra confusion to understanding what is going on.
-Jon
See http://www.electrical-contractor.net/forums/ubbthreads.php/ubb/showflat/Number/148726/page/2
One thing to add: I've seen diagrams where these are constructed using a bank of single standard phase transformers, which are often constructed as 480/240:240/120V devices. Since a zig-zag transformer needs to have the same number of turns, the HV side is wired parallel and the LV side wired series to make a 240V:240V transformer. This series/parallel connection just adds extra confusion to understanding what is going on.
-Jon
- Status