I have an project coming up for farmers nearby Mafeking.

The all have 3 phase motors on their bore holes.

My question is, is it cheaper to change the motor to single phase, or must I get a 3 phase inverter solar system?

Just a question from another angle. Depending on the use, is it not and option to invest in solar pumps with solar panels?

There are various reasons why getting a solar pump would be better.

 

Power factor, current requirements.

 

Three phase may well be more efficient which is important for solar. But it will cost a lot more inverter wise.

 

But a bad power factor will be really, really wasteful in which case an actual solar pump would be far better choice.

 

Power factor in 3 phase motors can easily be a problem, hence mentioning it.

There is a limit on the size of single phase motors. About a 5kW is the biggest I know of. If they are pumping large volumes of water then that necessitates a solar pump or remaining on 3 phase.

Also depends on whether it's submersible or above ground pumps.

Where can I get the best price on Submersible Solar pumps please?

Here is one place: http://www.solarsolved.co.za/index.php/products/submersible-pumps 

www.allpower.co.za submersible pumps are manufactured in SA. I have one and I am happy with it. They not as good as a Grundfos or Lorenz but

I'm sitting in the same boat. Need to solarize 3 pumps on the farm. One of them is an "ancient" pump that uses about 4.5A on 400V. It's a belt driven pump and the electrical motor is probably 10 years old. The one quote I got for a 2.2Kw solar system was R72,000!

What backup can I use for a submersible pump. If the sun is not shinning for more than 7 days?

I think that 7 days without sun  would be so infrequent event that  a generator would be the cheapest option if grid is not going to be available.

What backup can I use for a submersible pump. If the sun is not shinning for more than 7 days?

Probably rain quite a bit during 7 days without sun.

Any above ground tanks to pump into during sunny times ?.

What backup can I use for a submersible pump. If the sun is not shinning for more than 7 days?

Batteries, but as Chris said it would be more economical to have a genset if the sun doesn't shine for 7 days!. 

Thanks very much for feedback!!!

If there is already 2phase power at the pump

 

The all have 3 phase motors on their bore holes.

If there is 3 phase already at the pump, why not use that in case of emergency?

Rural Eskom users pay through the nose - sometimes R2500 -R3000 in line fees, levies etc. BEFORE you have used a SINGLE unit of power. If you are going solar under these circumstances you do not want to maintain your Eskom connection for the "what-if" scenarios. You plow that R2500 into your installation and make other alternatives for rainy days.

I have the same problem and looking into Three-Phase VSD Solar Pump Controller MicroCare has one. You do need a VSD compatable drive.

The other option I found was at www.fullcirclesolar.co.za  -- They have one that runs on all moters.

Down side is that they all need around 500V ( Lots of panels ) 

Still worth it as the Eskom pump point alone coasts me R1800 a month.

 

An option would be to replace the 3P DOL starters with a 1P input - 3P ouput VSD.

On 5/2/2017 at 0:00 PM, jacobez said:

An option would be to replace the 3P DOL starters with a 1P input - 3P ouput VSD.

We ended up installed 3x 5KVA Axpert inverters + solar panels, which then could be used for other purposes as well. Other brands could also be used but this was the cheapest option.