Single phase variable speed controls for water pumps
Single phase variable speed controls for water pumps
(OP)
We are working on a geothermal system where we will need a rather efficient way of moving variable amounts of water. Due to the high duty cycle of this system, the thought came to mind to use a constant pressure, variable speed well pump system. It was my understanding that they were just using 3PH pump motors and a typical VFD configuration but in talking with some OEMs, it seems that they are able to speed control both a 2 wire and 3 wire, 1ph pump motor. In the 3 wire, they are sending current to the aux winding as well.
I realize the type of drive needed would probably need a basic PID loop to handle the pressure/speed commands but I am wondering if this is truly a different drive or if any 3PH VFD with PID functionality could be configured to do this? I am real soft on going to a specialty type drive and would rather use a more universal drive and set up the parameters specific for this application.
Can someone explain how they are effectively speed controlling a 1ph motor? Any link relative to the subject would be welcome as well.
I realize the type of drive needed would probably need a basic PID loop to handle the pressure/speed commands but I am wondering if this is truly a different drive or if any 3PH VFD with PID functionality could be configured to do this? I am real soft on going to a specialty type drive and would rather use a more universal drive and set up the parameters specific for this application.
Can someone explain how they are effectively speed controlling a 1ph motor? Any link relative to the subject would be welcome as well.





RE: Single phase variable speed controls for water pumps
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Single phase variable speed controls for water pumps
It is possible that if a 3PH motor is used with a VFD, we can easily protect the motor windings from overload thus making repair an option.
RE: Single phase variable speed controls for water pumps
Motor protection for a 3 phase motor or single phase motor controlled by a VFD is going to be no different, not sure what you were thinking there.
99% of all modern VFDs now provide basic PI or PID control capability.
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Single phase variable speed controls for water pumps
I realize that the 3ph motors are available, the issue is just that most of the pump companies in our area do not stock them in the 1-1.5HP size range so they would have to be ordered should one go down. Even a couple days down could be a big deal. I guess just buying a back up could be an option.
I think I do like the idea of using 3ph better. Even if the pump is a bit harder to get, the drive, which probably would fail before the pump, would be MUCH easier to service and get going again.
Jraef, I know you have tons of experience with VFDs, what might you reach for on this application? Most likely go for a 2HP drive and use a single pressure transducer for control and another mechanical pressure switch for high pressure emergency shut down. Obviously I would need one that will allow 1ph inputs but of course derated.
RE: Single phase variable speed controls for water pumps
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Single phase variable speed controls for water pumps
You should also check the speed limits of the pump you use. Many submersible pumps won't like running at a low speed with low flow. Most use the flow to cool the motor and some use the pressure to support the rotating parts vertically.
RE: Single phase variable speed controls for water pumps
RE: Single phase variable speed controls for water pumps
The OP mentioned geothermal, which immediately suggests a high head application.
----------------------------------
If we learn from our mistakes I'm getting a great education!