Open Delta Transformer
Open Delta Transformer
(OP)
Have a facility which derives 3 phase 460 volt from single phase supply on open delta system according to FPL (Florida Power and Light), 3 phase pump motors are burning out from this supply due to severe amperage imbalance.
Advise..is fitting variable frequency drives a solution to this problem?
Advise..is fitting variable frequency drives a solution to this problem?






RE: Open Delta Transformer
You can derive 3-phase from single phase thru the use of converters, and VFD is one of them.
RE: Open Delta Transformer
What size is your motors?
RE: Open Delta Transformer
I do not think I have seen a 480 volt open delta installation.
RE: Open Delta Transformer
RE: Open Delta Transformer
One of my stations has a three-phase open delta utility feed.
old field guy
RE: Open Delta Transformer
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RE: Open Delta Transformer
I count three primary wires on your diagram, A,B, and N. The primary is open wye, not single phase and not three phase.
Any advantage to this three can version over the normal two can one?
RE: Open Delta Transformer
RE: Open Delta Transformer
It is a connection used to derive three phases at 120/208 volts, or 240/416 volts from two primary phases and a neutral.
The advantage:
Open delta with two transformers will supply either a three wire or four wire system. The four wire system may be 120/240 with a wild leg.
Cuky2000's diagram will supply a 120/208, four wire system.
Take your pick.
respectfuly
RE: Open Delta Transformer
RE: Open Delta Transformer
RE: Open Delta Transformer
ht
This sketch with two transformers provides more information including connection and vector diagrams showing the electrical phases.
RE: Open Delta Transformer
RE: Open Delta Transformer
Can you find a vector diagram for your first post with three transformers? It is a unique way of deriving a 120/208 volt wye system from two primary phases and a neutral.
Respectfully
RE: Open Delta Transformer
I could not find easily a wiring diagram. I guess that we need to create one. This may be fun for all of us.
RE: Open Delta Transformer
Note that transformer 1 and transformer 3 are wired for 120 volts.
Transformer 2 is wired for 120:240 volts.
To sketch the vector diagram, draw a "Z" All three lines are equal length and the included angles are 60 deg.
Label the nodes in order, 1,2,3 and 4.
Now extend the center line past node three a distance equal to the original length. Label the end 5.
This is your vector diagram. Nodes 1, 4, and 5 are the three lines and node 3 is the neutral.
1-2 is transformer 1.
2-5 is transformer 2.
3-4 is transformer 3.
Transformer 1 and transformer 3 are both fed from the same primary phase and their respective vectors are parallel.
A 120/208 volt system derived fro two primary phases and a neutral.
Disclamer: I originally learned this connection from a fellow poster on Eng-Tips. I mentioned it to a utility engineer who knew it as a Winnipeg connection.
respectfully