1ph vs 3 ph cost savings??
1ph vs 3 ph cost savings??
(OP)
I am aware that some areas, primarily in the western US, both irrigation and downhole pumping are using single phase source to a VFD acting as a phase converter then the 3 phase pump motor. But I'm having a problem seeing the cost justification in this scheme. It seems to be mainly 5 to 70hp. But once the drive is oversized by 75 to 100%, then the cable is oversized likewise, then you compensate for the horrendous single phase current distortion with an expensive filter, can there really be that much savings in running the 3rd wire. Especially when with 3 phase the wire is smaller? Help me4 under stand the cost justification of such a system.
Neil





RE: 1ph vs 3 ph cost savings??
And by the way, the 1 phase supply cable is not necessarily going to be over sized with or without a VFD to convert it to 3 phase for the motor. The motor power remains the same, so the only difference is a few percent of VFD throughput efficiency loss in the circuit.
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RE: 1ph vs 3 ph cost savings??
Neil
RE: 1ph vs 3 ph cost savings??
The only other reason is if they have a system they want to control the speed of the pump. Say, the well has seasonal flow issues and they want to draw water at the make-up rate and not cycle the pump. Then, of course, a VFD can help there.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 1ph vs 3 ph cost savings??
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 1ph vs 3 ph cost savings??
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: 1ph vs 3 ph cost savings??
Neil
RE: 1ph vs 3 ph cost savings??
Although this may be true in many cases, this is not a safe assumption. Protection schemes based on assumptions may not provide the best protection.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 1ph vs 3 ph cost savings??