Haider

2 more...  from my Win XP PC @ home; the look is a bit different to other OSs.

First thing that jumps to mind is the huge battery bank you are trying to charge with the 25A from the infini. The standard charging current should be about 1/10th of the Ah rating of the battery bank - you have a 750Ah battery bank and it should be charged at about 75A - you are charging it at 25A max, which is 1/3rd of the recommended / standard charging rate for your battery bank. Your inverter will really struggle to get the battery bank charged. It might work if you only discharged it say 10 to 15% every night and have good sunshine the next day, but if you drain the battery bank more than that every night, the inverter will not be able to recharge it to 100% during the day and after a few days of this, the battery bank will be dead - that said, this is when you have disabled AC charging and runs from the battery bank at night. If you are charging from PV and AC and runs the load from the grid at night it is OK, because then the battery bank will eventually be charged after a day or more depending on the DOD.
You also mention that the inverter trips when the the electricity goes (grid fails); does that happen during the day when you have enough sun (incoming PV) to cover the load or does this happen at night when the inverter has to fall over to the battery bank? What is the total load supplied by the inverter when it trips? Keep in mind that if your total load at any time is more than 3KW while the grid is available, the inverter will trip when the grid fails and the load is still more than 3KW, no matter if the incoming PV and / or battery is enough - the inverter can only supply a load of up to 3KW when the grid is not available. When you say "my requirement is to gentrate 3kw for home use for max economy" I suspect that your total load might be more than 3KW at certain times and that is why the inverter then trips when the "elecrticity goes".