Solar water pump selection

[trainpilot]

More pumping questions

I am looking to pump from a sump to a pond and am getting close to ordering equipment. 2hp 3-phase goulds we 20h submersible low head pump 230vac. I project the pump capacity to be about 121gpm against about 40' total dynamic head. I have found some information indicating that a variable frequency drive can be made to run directly off of panels if they are linked in series to provide the drive's dc bus voltage. See schnieder altivar drives. Does anyone here have experience with this type of system? It sounds like it might work well for OP's situation, and vfds are very flexible when it comes to programming pump speeds with different kinds of inputs.

[Solartopower]

Solar pumps options

I sell solar gear and solar pumps, to size the pump that you would need this is what i would need to know:
elevation (from water source to destination)
distance (from water source to destination)
Pipe size if existing
flow rate required (i can work this out for you if you know your tank/dam size and how long it takes you or your stock to empty it in in the peak of summer)

Mod note - no advertising please.

[inetdog]

I thought the controllers (from sun pump et al) converted the DC into PWM AC? I know you can put a clamp on AC meter on the wires from the controller and measure amps on the sun pump, which you normally cannot do on a DC circuit.

Some pump controllers convert DC to PWM AC with an approximately sinusoidal waveform and potentially multiple phases. This is required when the motor in question is an AC induction motor.
If instead the motor is a brushless DC motor, then it requires controlled (usually by PWM) DC applied to the various windings at the right times while the field is provided by permanent magnets or by a DC field coil.
But even then, part way through the rotation the controller will be applying a negative DC voltage to the same coils that it applied a positive voltage to earlier in the cycle. That means that an AC ammeter will read AC amps.

[Texas Wellman]

I thought the controllers (from sun pump et al) converted the DC into PWM AC? I know you can put a clamp on AC meter on the wires from the controller and measure amps on the sun pump, which you normally cannot do on a DC circuit.

[inetdog]

Thanks - I was curious what it meant and now I know

You are welcome Russ.
A very common place to find this kind of motor these days is in the traction motors of electric or hybrid vehicles where controlability and efficiency are at a premium.

[russ]

Not just chopped, but sequenced to different windings at different angles around the shaft, just as in a polyphase AC motor.
Or a chasing sequence Xmas light controller.

You could think of it as the DC equivalent of a VFD.

The "three phase" part would just indicate that there are three winding sets at 120 degree angular displacement.

Thanks - I was curious what it meant and now I know

[inetdog]

A chopped DC current then?

Not just chopped, but sequenced to different windings at different angles around the shaft, just as in a polyphase AC motor.
Or a chasing sequence Xmas light controller.

You could think of it as the DC equivalent of a VFD.

The "three phase" part would just indicate that there are three winding sets at 120 degree angular displacement.
You could make the motor with two or with 15 depending on what operating characteristics you need.

I think that the direct drive motors in modern front load washing machines work in the same way but with a very large number of poles compared to the number of phases.

[russ]

A chopped DC current then?

[cjb80]

Brushless DC motors use electronic commutation, and its sort of like poly phase AC, which smoothly drags the rotor around. The RPM's can be sensed by feedback in the power lines, and the controller knows how fast to switch the signals from wire to wire.

Cool, here is a link that I found that describes how it works.

http://fab.cba.mit.edu/classes/MIT/961.04/topics/brushless_DC1.pdf

[Mike90250]

Brushless DC motors use electronic commutation, and its sort of like poly phase AC, which smoothly drags the rotor around. The RPM's can be sensed by feedback in the power lines, and the controller knows how fast to switch the signals from wire to wire.

[cjb80]

Someone that knows will be along soon I expect.

Knows what? I am unaware of any open questions in my statements, except perhaps the details of what "three phase DC" means or how it is implemented.

Here is a manual for one of the controllers from Sun Pumps that uses this term: http://www.sunpumps.com/uploads/series/DocFile1_242.pdf
Look on page three or search for "three phase". I asked Sun Pumps what this means and if it has an inverter inside; they stated that there is no inverter and the description that they gave me on how it works is similar to what I stated in my previous posting. Anyways, their technical staff is pretty good so if you're curious I imagine you could give them a call and they'd tell you what's going on inside their electronics.

Chris

[russ]

I am aware that the term "3-phase DC" makes no sense, hence the quotes. In any case, that is the term that the company uses.

Someone that knows will be along soon I expect.

[cjb80]

3 phase DC?

I am aware that the term "3-phase DC" makes no sense, hence the quotes. In any case, that is the term that the company uses.

[russ]

Anyways, I have a 3 HP, "3-phase DC" pump and it works really well.

3 phase DC?

[cjb80]

correct me if i am wrong:

DC (brush less ) pump (submersible) maximum range around 10 HP

which better for solar DC pump 10HP or AC pump 10HP and what the difference pleasse ?

Thanks mike;

I don't think the efficiency of DC vs AC is the (important) issue, really. There are brushless DC pumps out there that are probably very close to AC pumps in terms of efficiency. If you ran solar with an inverter then I would have much more confidence in saying that a DC pump would be more efficient than DC->AC then running an AC pump.

The question you should be asking yourself is if a 10 HP DC pump is made by anyone. The company that I would call to discuss this is SunPumps. From what I have gathered, they take pump parts and put them together in various combinations and then run them using DC electronics. Their pumps are "3-phase DC", which means that it takes 4 wires and then it has an electronic controller that manages the power across three conductors in a manner that is similar to an AC pump. My understanding is shaky, but I think that the electronics choose a desired rotation speed (based on input voltage and various other settings) of the pump impeller and then trigger impulses across the three conductors in a synchronized manner with the rotation of the impeller.

Anyways, I have a 3 HP, "3-phase DC" pump and it works really well. It sounds like a jet engine. I know that SunPumps makes a 4 HP one but I am not sure if they go up to 10 HP... By the way, I have a ~3kw array to power 3 HP, so the array would need to be quite large to power 10 HP... (like 35-40 285 watt panels to make a 10kw array)

Chris