I am currently planning my borehole pump setup and contemplating the Microcare Solar Pump Controller with built in VSD:

My main reasons for choosing this option are because it runs battery-less, comes with all necessary electrical protection, has provision for 2 switches (NO & NC) and has passive cooling so it can be placed under the panels outdoors.

Does anyone have any experience with this unit or have any suggestions of an alternative to run a 1.5KW AC motor straight from the panels?

https://microcare.co.za/wp-content/uploads/2020/08/230V-Solar-Pump-Controller_3kW-3-Ph_1_5kW-Single-Phase-Manual-Version-2018-4.pdf

You also get the powtran ones from china.

It seems that they all work on the same principle - there is no boost stage, so your panels Vmp HAVE to be more than the peak of the AC waveform, so about 310VDC for 220VAC. That makes it quite difficult to find adequate panels to get you to the voltage you need, without installing way too much power (cost issue). Basically you have to have at least 8 x 72 cell panels to be able to run a 220VAC pump at max power.

Now these units, being VSD, will run the pump at lower power levels when less solar is available. That is sometimes not an issue, but for a borehole it can mean that the pump cannot overcome the pressure required to get the water to the surface, which can lead to the motor overheating and being permanently damaged.

(And of course your pump has to be 3 phase)

 

Thanks for your input @P1000, much appreciated.

1 hour ago, P1000 said:

That makes it quite difficult to find adequate panels to get you to the voltage you need, without installing way too much power (cost issue). Basically you have to have at least 8 x 72 cell panels to be able to run a 220VAC pump at max power.

I noticed that from the specs which was a problem at first, but luckily I found some 320W@72V and 330W@91V panels at Heroldts which are a good price, so I should be able to build the array I need.

2 hours ago, P1000 said:

Now these units, being VSD, will run the pump at lower power levels when less solar is available. That is sometimes not an issue, but for a borehole it can mean that the pump cannot overcome the pressure required to get the water to the surface, which can lead to the motor overheating and being permanently damaged.

Good point, thanks. I see these units have a 'min frequency' setting, so I figured as long as I set that high enough (with some testing) then it will ensure that the pump always gets the water out if/when running. Am I correct in my thinking?

2 hours ago, P1000 said:

(And of course your pump has to be 3 phase)

Thanks for pointing that out too, I was not aware of that. I was originally planning to run it in the 1.5KW single phase mode, but looking at my pump and motor options last night, I am going to go with a slightly different model now and switch to 3 phase 380V instead, so that works out.

I think this unit should do the job and leave me room to increase the borehole output in future if necessary and give me more flexibility with what pump motors I can run (most popular seem to be 380V and 400V):

Thanks again!

5 minutes ago, jumper said:

I see these units have a 'min frequency' setting, so I figured as long as I set that high enough (with some testing) then it will ensure that the pump always gets the water out if/when running. Am I correct in my thinking?

I think that should work.