Powering a VSD/VFD for a pump motor from an SMA solar inverter

Sunspark

Hi All. I am looking to take my 55kW 3-phase irrigation pump off-grid. My idea is to build a 100kW off-grid "island" (solar powered), which will supply enough day-time electrical power to drive the irrigation pump as well as my other workshop loads (compressor, welder, etc.).

I have however been told that it is risky to drive a VSD/VFD controller from a solar inverter, as the VSDs/VFDs apparently aren't very well behaved if they are not powered from a near perfect / smooth AC waveform supply (as one would get from the utility grid or a rotating generator). My assumption has been that "true sinewave" solar inverters are actually, well, true sinewave.

Do any of you fine folk have experience with driving a multi-kW VSD/VFD from a solar inverter? Would line filtering be required / enough to smooth the inverter's AC output for the VSD/VFD to be happy?

Thanks!

mike95490

The actual issue is with the strange harmonics the VFD & Motor generate.  In the industry, there are many instances of a perfectly fine 3 phase motor, fails with VFD.  The Generated Harmonics can (and are likely) to not be friendly to the PV inverter output.

I'd suggest you construct a 3 phase 480VAC solar grid with 3, phased inverters, and run the motor directly from that.

Otherwise, a 60KVA isolation transformer with additional high frequency filtering, may protect the PV inverter from the VFD

Again, it's not the PV inverter that is the problem, the VFD creates a problem, and you need to protect the PV inverter

It's not likely you can do this without batteries, unless you keep the grid (recommended) and use your PV array to backfeed and sell surplus power to the grid, or only for self-consumption without any backfeed agreement..

The Schneider gear scales up to 61kw
https://solar.schneider-electric.com/solution/commercial-self-consumption/

 battery-less systems will not produce any power if the grid is down or out of spec with voltage or frequency.

here's some stuff to read

https://www.ecmweb.com/power-quality-reliability/harmonics/article/20896318/the-411-on-variablefrequency-drives

excerpt:
 12-pulse VFD
A 12-pulse VFD has phase shift transformers ahead of 6-pulse VFD to cancel the harmonics reflected back to the source. The phase shift transformers can be tuned to reduce harmonic distortion to less than 10% at the input terminals of the VFD (click here to see Fig. 3). The windings of the transformers are offset to cancel the largest harmonics from the VFD. By reducing the harmonics at the input terminals, the intent is to reduce voltage distortion at the source because the current THD at each piece of equipment is reduced.
~~~~
 Before selecting a VFD, evaluate the current THD. A 6-, 12-, 18- or even 24-pulse VFD should be evaluated to determine the best solution. Harmonics can cause faulty meter readings, motor bearing failure (due to electrical currents), blown fusing on capacitors, and/or telephone communication interference. A possible effect of harmonics is excitement of a system resonance that can significantly raise the voltage and cause system failures.
~~~~~
http://www.gohz.com/the-most-common-causes-of-vfd-failure
   Every engineer has good points about variable frequency drive (VFD) failure reasons. Some of the phenomenons occur more frequently and some are rarer.