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Kilowatt Power

Can 15kW Axpert Inverters Start 9.3kW Submersible Pump?

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Greetings,

Can 3 * 5kW Axpert inverters in 3-phase parallel configuration (total 15kW) start a 9.3kW/12.5HP 415VAC 3-phase submersible well pump? 

I've not gotten to measure the pump's inrush current but it's a typical multistage centrifugal pump with an asynchronous squirrel cage motor manufactured by Silver Pumps & Motors (India).

NB: The housing complex cannot increase installed capacity of the water storage tank hence the need for at least 2 hours power backup in lieu of a diesel standby generator set. 

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I've been investigating a second option of directly coupling a 576VDC lead acid battery bank (48 * 12VDC * 65Ah batteries in series) to the DC bus of a 15kW Variable Frequency Drive but I cannot find a constant current regulator/battery charger operating near 600VDC.

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On 2019/11/11 at 1:16 AM, Kilowatt Power said:

Can 3 * 5kW Axpert inverters in 3-phase parallel configuration (total 15kW) start a 9.3kW/12.5HP 415VAC 3-phase submersible well pump? 

I wouldn't think so, without some sort of soft start device or VFD set up to do a soft start.

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I wouldn't think so, without some sort of soft start device or VFD set up to do a soft start.

I agree with you. I got to measure the inrush current using a UNI-T UT216C clamp meter and the pump is gobbling 77.6A at startup then roughly 21A during normal running. Mind you this is at 415VAC. The starting power requirements are simply beyond what 3 * 5kW Axperts in parallel configuration could offer. i.e. 32.2kW vs  30kW peak power.

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Mmm. You would need 415x1.73*77.6, or 55 KVA...

Thanks for the kW = 1.732*V*I*PF/1000 correction

On 2019/11/14 at 12:59 AM, Javi Martínez said:

You only need a DC VFD, no inverter is needed 

Any pointers to a suitable battery operated DC VFD in the market?

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4 hours ago, Kilowatt Power said:

Any pointers to a suitable battery operated DC VFD in the market?

Any VSD will manage the slow start (and lower start up current) 

These devices generate their own DC bus from AC power being fed to the unit so no need for the external batteries.

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On 2019/11/13 at 9:58 PM, Kilowatt Power said:

I agree with you. I got to measure the inrush current using a UNI-T UT216C clamp meter and the pump is gobbling 77.6A at startup then roughly 21A during normal running. Mind you this is at 415VAC. The starting power requirements are simply beyond what 3 * 5kW Axperts in parallel configuration could offer. i.e. 32.2kW vs  30kW peak power.

Do you have the Axpert inverters already?

If so what I would do is to start the pump with regular power and then simulate a power outage and see if the inverters will keep the pump running. If so we can then address the startup current peak..

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32 minutes ago, PJJ said:

Well its the cheapest way of getting to 15KW without going to the really dumpster fire section of the inverter world.

Man! What an absolutely brilliant way to put it 🙂

I need fresh coffee... this cup has some mucus drifting in it now...

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1 hour ago, PJJ said:

Well its the cheapest way of getting to 15KW without going to the really dumpster fire section of the inverter world.

Is that synchronised 3 phase (i.e each phase 120 deg with respect to each other)

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37 minutes ago, Richard Mackay said:

Is that synchronised 3 phase (i.e each phase 120 deg with respect to each other)

Yup, you do need 3 inverters tough, one for each phase, in Program 28 on the Axpert you can assign each inverter to its respective phase.

You will also get a fault code 82 in event of a synchronization loss (Or well atleast that's what I can gather from the Axpert manual)

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1 hour ago, PJJ said:

Yup, you do need 3 inverters tough, one for each phase, in Program 28 on the Axpert you can assign each inverter to its respective phase.

You will also get a fault code 82 in event of a synchronization loss (Or well atleast that's what I can gather from the Axpert manual)

Has anyone implemented this config in the real world and able to provide some feedback??

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23 minutes ago, Richard Mackay said:

Has anyone implemented this config in the real world and able to provide some feedback??

I have never done it, but in theory it should work, but lets call the resident Axpert expert @Youda

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A friend of mine is using this setup to power his workshop, including all the 3-phase machines and tools.
The setup produces nice and clean 3-phase power with the correct phase-shift between the phases.
The grid is not needed for the start, you can use this even when you're completely offgrid.
Works with a 1-phase loads too, it's capable of supporting assymetrical phase load.

 

BTW: In my own setup, I'm using a different gear, three InfiniSolar inverters working in parallel in a 1-phase 15KW system.

 

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23 hours ago, Kilowatt Power said:

Thanks for the kW = 1.732*V*I*PF/1000 correction

Any pointers to a suitable battery operated DC VFD in the market?

It is not as you say. Starting, It will be:

KVA = 415 * In * 8 * 1.71/1000

KW = 415 * In * 8 * 1.71 * 0.25/1000

You have to consider cos phi will be round 0.25 at start.

Inrush current will be much higher that you measured, round 8 times nominal current.

Edited by Javi Martínez

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11 hours ago, Javi Martínez said:

As I said before, you only need a solar VFD and 15 Kwp of solar pannels. No batteries, no charger, no inverters...

https://www.zuendo.com/ls-solar-trifasico-380-v/2863-variador-de-frecuencia-solar-trifasico-11-kw-ls.html

 

I had this in mind and had even proposed the INVT GD100-011G-4-PV solar pumping inverter with 16S3P Jinko 330Wp panels (total 15840Wp) but the client wants to be able to run the pump at night. Needless to mention, doubling or even tripling the installed 20m3 water storage tank capacity would have been the best route to follow. 

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5 minutes ago, phil.g00 said:

Use a CT & the "Max" function on a multimeter, measure at the top while starting.

UNI-T UT216C clamp meter has an "inrush" function. The "max" function would measure the maximum steady state current which would be around 23A.   

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