The configuration should work for linear, non linear and unbalance.
Edit: This configuration have to work for deltaload and without transformer.
I also suggest you to use 3 leg as it is more practical and better than full bridge. you can see we analyse the signals
In general 3 leg configuration is more cost effective, however the system shall be well balanced. If this is not the case, 3 single full bridges is the solution.
Thank you all for your valuable solutions. Please see the edited question details. In full bridge config, formation of delta connection isnt possible i guess. Comment your views on this.
Delta load should not cause big problems. Y connection would be critical for 3 leg configuration, because the neutral line current has to be zero.
Delta configuration with 3 full bridges can be achieved by switching pairs of half bridges simultaneously (acting as a 3leg inverter) :)
Star configuration would be "trickier" but not impossible.
Important for any transformer-less design: your DC link may bot be grounded and will "swing" around significantly (regarding to earth ground). Thus, on the DC link side, capacitances to earth ground are to be avoided.
3 leg is batter for 3-phase but if you are working on distribution system it will be 3-phase 4 leg inverter suitable.
Three leg three phase is the best option for the practical implementation. you can use different PWM scheme according to your requirement.
Mr.Dreher, can you provide paper/article to support theory of three phase full bridge config? I couldnt find one.
3 leg is better.
you can also use MLI for the same purpose with reduced number of switches.
Hello Jaikumar,
sorry - currently I'm not able to provide any paper. My comment regarding 3 leg full bridge is from own considerations regarding "alternative" configurations in a very early stage of specification. So it is easily possible that no integrated devices exist currently. But there is always a way to combine exiting devices.
The original intention was to be able to switch between star and delta configuration to overcome system restriction in a very special application (application not to be disclosed here).
If you are somehow familiar with star-delta configuration, it is clear that you have to control all "ends" of the 3 wires - leading to the request for 6 half or 3 full bridges. The rest is about bridge control. But it should be clear that for a delta configuration the "end" of one phase and the "start" of the next phase always have to be at the same potential. (This is, how delta configuration is defined.) Thus in delta configuration you may "logically short" the half bridges in pairs.
The trickier part is the star configuration which I did not work out in detail up to date.
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