Single phase or three phase solar pump

[bobiyanev]

Hi.
Plan to install AC solar pump system for orchard irrigation. Pump calculated at 1.5 kW as per well and irrigation system. Planned solar pump inverter at 2.2 kW. Still wandering of pump power supply - single phase 220AC or three phase 220AC. Market offers both type of inverters. Which type is more reliable and efficient? Read in monophase inverter manual of eventual pump motor capacitor removal and wasn't convinced of reliability and pump compatibility. Is three phase a better choice?
Thanks.

 

[MisterSandals]

Good question!
@MichaelK pumps a lot of water. Maybe he has an answer.

 

[SkyBlue]

Does this thread help?

The Benefits of Three Phase AC Pumps For Solar Water Pumping

I’ve been operating submersible well pumps for more than four decades. I’ve installed, repaired, and replaced many pumps. The reason for this post is to encourage anyone operating, or planning to operate a submersible pump on solar power, of the significant benefits of powering the pump with...

diysolarforum.com

 

[bobiyanev]

Thanks SkyBlue. Very usefull info.

 

[hwy17]

That link talks a lot about benefits of running three phase pumps specifically through a single phase AC to three phase AC VFD converter.

Three phase pump from three phase inverter still draws inrush current unless I don't know anything.

If this a dedicated solar system for irrigation pumping that only needs to run during solar production I would consider direct solar pump options.

Solar water pumping systems

Grundfos is dedicated to pioneering the future of water technology, and our range of renewable energy powered products does just that.

product-selection.grundfos.com

 

[bobiyanev]

Was looking at DC pumps as well, but Grundfos and Lorentz are very expensive, chinese pumps bought from Internet are cheaper but these have no warranty. Market for these pumps is quite small and it's much easier to find correct AC pump for needed flow and pressure. DC pumps in general are more expensive than respective AC pumps, which covers price of the solar pump inverter and the extra panels.
Three phase pumps, running through solar pump inverter can be set to start and speed up gradually, avoiding high starting current and can be ran at frequency lower than nominal.

 

[hwy17]

Oh I see, so you're already looking at direct solar pump inverters, with no battery?

I don't know then but I would have to guess 3 phase is a lot more ideal in that application.

 

[OzSolar]

I can't say about Bulgaria but I can say that in the US three phase pumps won't make any sense in that 1.5kW range.
I'd offer that you have several options.
#1- Start off with a Grundfos (buy once-cry once) or
#2- Take your chances one of the many options available on Alibaba.

We've done several of both and to be honest I'm actually blown away by the performance and durability of the pumps we've picked up on Alibaba.

We've got a couple of Alibaba pumps that are running at ~30 gpm at 150' of TDH on less the 2kW of PV. Those pumps cost us somewhere around $300 delivered and that included the controller.

 

[bobiyanev]

Thanks OzSolar.
Looked at Chinese pumps and found several options. Can you recommend brands, if the Forum allows? With such price of the pump and controller and reduced number of panels it's worth considering.

 

[MichaelK]

I basically designed my system around the single-phase pump already in the ground. With my inrush numbers in hand, I ended up selecting the split-phase XW+ 6848 as my inverter. It has performed wonderfully!

Three-phase may be more efficient, but you'll need three parallel inverters to supply that. It may be more cost effective to have a somewhat less efficient single phase pump that only needs one inverter to run?

 

[hober]

three phase 220v

 

[OzSolar]

Thanks OzSolar.
Looked at Chinese pumps and found several options. Can you recommend brands, if the Forum allows? With such price of the pump and controller and reduced number of panels it's worth considering.

It's definitively worth considering. We've bought several pumps from Ningbo Jilu. When factoring in that Alibaba is not like working with a standard retailer our experience has pleasant.

 

[v_brothers_ranch]

I've got a lot of different pumps from over the years out in different pastures for stock tanks and central distribution tanks but not for irrigation. My understanding of those types of projects on solar is that they also involve much greater pressure and so you need to size up to accommodate (sp?) that pressure head. Sorta pretending like it has to overcome an extra 100 feet of head for a normal sprinkler. I have a few pumps that have some drip tape on the way to the tank that I have a few pots and flowers for my wife, but that is lower pressure as those seem to drip even when I just close the gate valve on the water outlet into the pump a tiny bit. Probably a couple psi but I dont have a gauage there. The other thing that maybe I could offer for advice is to get a bigger solar array then you think you need for the pump. (but in parallel so you dont blow anything up!) That gives you a longer possible day (weather depending but we get lots of sun on our ranch) that you can actually pump water. I'm not sure if I imagine it properly and I think an electrical engineer in here might correct me but I think of it like a bell curve of solar throughout a normal sunny day and the more solar the wider the curve. Whatever power the pump needs to pump is a horizontal line across that curve. I've got some smaller pumps that seem to come on at like 100 watts or something and so when I have 360-400 watts of solar on it, it starts at like 8am and pumps until beer oclock or so. I think for the style of pump its more about what is available local. The only way I can get those big expensive brands is to hire out installation and they charge a ton. If you buy anything online, amazon or the past few recommendation you just dont get a warranty at all. The really cheap ones I think just plan on replacing every month as they are cheap brushed motors. Try and find one that has a brush-less motor controlled by a surface controller. That means the controller at the surface is operating the motor and a lot less can go wrong. Well, I have busted (or the cows have) just about everything once by now, but I'd rather replace something on the surface then haul up a pump from a well 200ft deep! My understanding (and again someone more experieinced will tell me) that a DC brush-less and a 3phase motor are pretty similar and both more efficient. (I also would advise heavily against going single phase 220v whenever doing solar or inverters as like other said they are super hard to startup for solar arrays or battery banks) My experience is less theoretical and more trial an error. I have tried all the brands and all the different styles. I will say that if the price seems too good to be true it usually is. I have most success with the higher quality middle of the road companies that are in the USA so they answer the phone. Not sure international options though. I have a lot of water stress about thirsty cows and so I put a lot of heart into water solutions. (I have a few old windmills that I have kept too but most i have converted to solar or done a hybrid on) I havent done as much irrigation but if you love plants like we do cattle I imagine you want to do it right the first time. Sorry for the long answer!

 

[Supervstech]

I've got a lot of different pumps from over the years out in different pastures for stock tanks and central distribution tanks but not for irrigation. My understanding of those types of projects on solar is that they also involve much greater pressure and so you need to size up to accommodate (sp?) that pressure head. Sorta pretending like it has to overcome an extra 100 feet of head for a normal sprinkler. I have a few pumps that have some drip tape on the way to the tank that I have a few pots and flowers for my wife, but that is lower pressure as those seem to drip even when I just close the gate valve on the water outlet into the pump a tiny bit. Probably a couple psi but I dont have a gauage there. The other thing that maybe I could offer for advice is to get a bigger solar array then you think you need for the pump. (but in parallel so you dont blow anything up!) That gives you a longer possible day (weather depending but we get lots of sun on our ranch) that you can actually pump water. I'm not sure if I imagine it properly and I think an electrical engineer in here might correct me but I think of it like a bell curve of solar throughout a normal sunny day and the more solar the wider the curve. Whatever power the pump needs to pump is a horizontal line across that curve. I've got some smaller pumps that seem to come on at like 100 watts or something and so when I have 360-400 watts of solar on it, it starts at like 8am and pumps until beer oclock or so. I think for the style of pump its more about what is available local. The only way I can get those big expensive brands is to hire out installation and they charge a ton. If you buy anything online, amazon or the past few recommendation you just dont get a warranty at all. The really cheap ones I think just plan on replacing every month as they are cheap brushed motors. Try and find one that has a brush-less motor controlled by a surface controller. That means the controller at the surface is operating the motor and a lot less can go wrong. Well, I have busted (or the cows have) just about everything once by now, but I'd rather replace something on the surface then haul up a pump from a well 200ft deep! My understanding (and again someone more experieinced will tell me) that a DC brush-less and a 3phase motor are pretty similar and both more efficient. (I also would advise heavily against going single phase 220v whenever doing solar or inverters as like other said they are super hard to startup for solar arrays or battery banks) My experience is less theoretical and more trial an error. I have tried all the brands and all the different styles. I will say that if the price seems too good to be true it usually is. I have most success with the higher quality middle of the road companies that are in the USA so they answer the phone. Not sure international options though. I have a lot of water stress about thirsty cows and so I put a lot of heart into water solutions. (I have a few old windmills that I have kept too but most i have converted to solar or done a hybrid on) I havent done as much irrigation but if you love plants like we do cattle I imagine you want to do it right the first time. Sorry for the long answer!

Oof… tough post to read.
Try to use the enter key every so often…

Give some paragraphs to make it easier to read please…

 

[time2roll]

Three phase and motors is a slam dunk every day of the week.

 

[smr.ruby]

Agree on the three phase. I run an off-grid system with an EG4-6000EX powering my pump drive and other RV loads, tools, etc. Once you get AC power out of the inverter there is nothing solar specific about my water system. I do think that most of the well pump specific drives are very over priced though ($2000+, argh). You can get an industrial grade 1 to 3 phase VFD for much less, smaller footprint, implement exactly the same protections in it and have modbus and bluetooth for remote communications, easily implement dynamic pressure control.

my drive is a Yaskawa GA50UB010ABA - can buy new for under $400 sometimes.
pump is a Goulds Centripro M20432 - well depth 800ft

ABBs drives are great too.

Just make sure you don't run the drive/pump slower than 30Hz. These vertical axis well pumps rely on some axial forces from pumping to keep weight off the bearings. Too slow for too long is just hard on the bearings. I typically run full flow at about 45hz and it ramps up nice and slow and draws about 1500-1800watts.

 

[smr.ruby]

Three-phase may be more efficient, but you'll need three parallel inverters to supply that. It may be more cost effective to have a somewhat less efficient single phase pump that only needs one inverter to run?

You only need one inverter, the pump drive or variable frequency drive (VFD) makes three phase from single phase and at varying frequency to control pump speed.

 

[smr.ruby]

That link talks a lot about benefits of running three phase pumps specifically through a single phase AC to three phase AC VFD converter.

Three phase pump from three phase inverter still draws inrush current unless I don't know anything.

There would be inrush running the three phase pump directly from the inverter but there is no inrush running a three-phase pump through a VFD or "pump drive." The VFD also acts as a soft-start and slowly charges its capacitors and then ramps the pump from 0-XXhz over some set period - I think mine is on a 5 second ramp. The end result is that it draws very little starting current and ramps up slowly to full current at run speed.

 

[Hedges]

Three-phase motors have just as high a starting surge as split-phase, but better torque.
The ideal setup would be a VFD with MPPT built in, and PV array oriented multiple directions for more flat power output.
For a larger system, rather than running one large or many smaller pumps all at varying speed, leave some pumps off and run others at most efficient RPM, ramping up additional pumps when more power is available.

Some people have said pumps rely on a water bearing, and slow start accelerates wear. Start infrequently (once per day) and don't operate below a certain speed (easier said than done with clouds.)

Although in the couple kW range, you can just buy a good inverter and start split-phase or 3-phase motor with enough "oomph".
Check out the new Midnight Rosie. Or use Schneider, Sunny Island, or ... (all battery inverters. Use AGM battery for starting surge, and shut off pump when PV doesn't produce enough.)

 

[smr.ruby]

Three-phase motors have just as high a starting surge as split-phase, but better torque.
The ideal setup would be a VFD with MPPT built in, and PV array oriented multiple directions for more flat power output.
For a larger system, rather than running one large or many smaller pumps all at varying speed, leave some pumps off and run others at most efficient RPM, ramping up additional pumps when more power is available.

Some people have said pumps rely on a water bearing, and slow start accelerates wear. Start infrequently (once per day) and don't operate below a certain speed (easier said than done with clouds.)

Although in the couple kW range, you can just buy a good inverter and start split-phase or 3-phase motor with enough "oomph".
Check out the new Midnight Rosie. Or use Schneider, Sunny Island, or ... (all battery inverters. Use AGM battery for starting surge, and shut off pump when PV doesn't produce enough.)

All of the pump manufacturer's own drives slow/soft start on purpose with no impact on warranties etc. I can't find a spec for my 4" pump and motor anywhere but the 6" and larger motors from the same manufacturer say ramp up should be set to get to 30hz in 1 second or less (page 12). There should be concern with accelerated wear from continuous slow operation (eg hours at 10% speed), but slow start - even multiple times per day - is typical operation in most uses (agricultural, residential, etc). So slow but not "too slow" is fine.

If you are running a VFD to make the three phase power for the three phase motor there is no "oomph" or starting surge, it never draws more current during startup than it does at full speed - ramp is a nice climb from 0Amps to whatever is required at the operating speed/load.