2 pumps in parallel, how many inverter

samijlaielsamijlaiel Registered Users Posts: 3

Hi Guys,

Happy to joint you.

I am using solar water pump for olive trees irrigation.

I installed 2 years ago 30 panels (260w each, and 15-15 in parallel) to ABB ACS355 inverter wired to 4kw submerged pump at 40 m depth and delivering 15m3/h.

I would like to pump the water in 50m3 tank. Then I am thinking to install a 1.1 kw centrifuge pump for drip installation delivering 25m3/h commanded by float switcher.  I wonder if I can add more panels (6 for examples) to my old panels to become 18-18 in parallel. In the first 3 hours I will get the full pumping rate from the well till 50m3 level because the centrifuge pump will be off. By this time the lighting will be enough to run the 02 pumps for at least 4-5 hours in sunny day (we have nice sunny days in Tunisia).

My questions are: Can I connect this 02 pumps to 36 panels together and how or should I wire each pump to its own panels and inverter?

Comments

  • jonrjonr Solar Expert Posts: 1,310 ✭✭✭✭

    If the 3 phase inverter drive can handle the maximum voltage your panels will produce and the output amps you need, then I'd use it for the second pump too.

    I am available for custom hardware/firmware development

  • samijlaielsamijlaiel Registered Users Posts: 3

    Thank you for your answer,

    I am sure the inverter can handle the voltage (I tested it with 19 panels in series). My question can I wire the 02 pumps in parallel to the same inverter and no need for a 2nd? 

    In case of cloudy time or insufficient lighting, how will be split the lack of power? Which pump will run with the lower Hz or their frequencies will be equal?

  • jonrjonr Solar Expert Posts: 1,310 ✭✭✭✭
    edited February 20 #4

    Generally yes, pumps can be wired in parallel. The frequencies will be equal. Two inverters would allow you to control the pump speeds independently.

    Power split (with a shared inverter) is hard to predict, but in low light, you will need to dial down the speed/power to what the panels can produce.

    What maximum voltage do you expect from 19 panels in series? As far as I can tell, the AB355 is never rated for more than 480V input.

    I am available for custom hardware/firmware development

  • BB.BB. Super Moderators, Administrators Posts: 29,636 admin

    I would suggest that you do not parallel 3 phase AC induction motors on a single VFD.

    The VFDs use feedback from the motor as part of their controller operation. Not sure what would happen with two motors on one output.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • samijlaielsamijlaiel Registered Users Posts: 3

    Really, I don't have the exact value on hand now but I started by 19 panels to run 4kw pump. It gave only few hours per day. Then I put 30 (15-15). Flow is still not enough. ABB agent, when I wanted to replace the 4kw submerged pump by 5,5 kw, advised me to add 6 panels more. Now I prefer to increase the flow to feed the entire drip installation by centrifugal pump and tank. So the main problem is can I wire 2 different pumps to one shared inverter and How it will be the split of power in case of low lighting?

    Thanks

  • BB.BB. Super Moderators, Administrators Posts: 29,636 admin

    One way to configure the VFD is to adjust the output frequency based on the input Panel Voltage/Current (aka MPPT--Maximum Power Point Tracking--Looking to "solve" the equation Pmp=Vmp*Imp -- The MPPT controller "adjusts" I current to keep V voltage from array at the optimum value -- As the sun sets, I must fall in order to keep Vmp at the desired operating point).

    As the solar array available power falls, then the VFD reduces output frequency (pumps turning slower with roughly same torque, lower power requirements).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,310 ✭✭✭✭

    > One way to configure the VFD is to adjust the output frequency ...

    I assume that you mean manually - as far as I know, the ACS355 doesn't have a built-in MPPT option. Or even a simplified version (reduce output when input voltage falls to X).

    Here is an article about multiple motors on a single inverter/VFD.

    https://www.automation.com/library/articles-white-papers/motor-drives-control/vfds-can-control-multiple-motors

    I am available for custom hardware/firmware development

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