SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
Is there a book or a web site i can more information on this??
Try http://www.3phasepower.org/2phasesystems.htm
Is there a book or a web site i can more information on this??
??? You should have 170 volts phase-phase if you have 120 volts to the common on a 2-phase.
On 2-phase it is:
V12 = sqrt(V1^2 +V2^2)
Not if you use two of the 4 phases that are 180 degrees apart (120 + 120 = 240). If you use 2 phases that are only 90 degrees apart then yes, 170v.
Then you do not have what is traditionally called 2-phase.I'm not sure that I follow ... looking through my notes, I see that it is a 4W240/120 open delta. They have one 25KVA transformer and one 50KVA transformer w/ a center a tap.
See attached PDF ... option III we are talking about here.
The 3-phase side has line currents of I3 = VA / (sqrt(3) x V3_line-line) amps.The result of all this is that I am going to specify a Hammond Solutions custom built Scott T transformer, 150KVA, 240V, 2-phase, 5-wire input and a 120/208V, 3-phase, 4 wire output in order to covert the entire OLD 2-phase, 5-wire service to a new 3-ph service. I confirmed with Hammond that they can build this in about 4-weeks to these specs. I know how to calculate the secondary current of the 120/208V, 3-phase secondary ....but I am uncertain how to calculate the input primary current on the 2-phase,5-wire side of this Scott T configuration for the four phase conductors. This sounds like a PE exam question, but does anyone know how this would be done so I can make sure the incoming primary fused disconnect switch and conductors are sized appropriately?
Yes. As usual, energy is conserved and for balanced loads at unity power factor it is just simple math. No engineering degree required, so all you electricians knock yourself out. :grin:I bet the people making the transformer can tell you.
Added: The normal method of converting secondary load at its kva to the primary load at the same kva should work.
Then you do not have what is traditionally called 2-phase.
In a strict technical sense, you do have two phase, but it is not the same as what has been historically labeled as "two-phase" in our industry.I'm confused as to how ... two phases are present on the lines, why don't I have that? So, what's the diagram of two phase?