I need occasionally drive watergate. Because location is far away from *220V* I suppose powering from *SLA 12V battery* charged from solar panel. Battery capacity *7-20Ah*. Required motor power is *50-100W* (torque I think >0.2Nm). Because of outdoor usage I need *IP66* or so. Price is also essential.

I did not find any 12V DC motors and seems that **3 phase AC motor** produced in large quantities is the only option.

I can use *power inverter 12V-DC/220V-AC and 3 phase frequency changer* (e.g. Sinamics G110) to power motor even with trapezoidal profile. Expected efficiency 85%*95%. It could be assembled from stock products and it should work. I don't think it's worth to do it as home-made application. 

I wonder if I can do it much simpler when I make simple **inverter** (IRS2153+current sensing IR2127+FETs+toroid transformer 2x12V/220V) and connect to **3 phase motor using Steinmetz method**. Output of inverter is rectangular 220V voltage with adjustable frequency (easy to implement IRS2153 has option to force switching frequency from MCU).
[![enter image description here][1]][1]

The questions are: 

1) Steinmetz decrease motor power to 70% and starting torque to 50%. But I believe **efficiency** remains unchanged, i.e. in other words I can use stronger motor without power loss compared to regular 3-phase triangle connection. Is it true ?

2) Is it possible to **regulate motor revolutions via changing of inverter output freqeuncy** (i.e. apply trapezoidal profile) ? I'm uncertain how Steinmetz capacitor value (70uF/1kW) is related to voltage frequency (50Hz).

3) how motor copes with **rectangular AC** waveform? I think it may affect insulation bacause of voltage peaks.


  [1]: https://i.sstatic.net/iPZGC.png