we have total load of 3500 A, Voltage 220v/1Ph/50Hz, we are in need of a three phase generators which may feed this amount amount of load, this total load is on Red , Yellow, Blue phase on the secondary side.. the power factor is 0.8. we are in need of the capacity of the generator...

 

Cool.

 

I suggest you read this. You really need to much better describe your needs because you have said very little. You start with 3,500 amp load at 220 volts? Then you mention going to 3 phase? Motors, big compressors, pumps, large heating elements? That 3,500 amps at 220 volts is around 770 KVA on a single phase 220 VAC line and makes no sense. There are many things to consider when making large commercial generation decisions and you haven't come close to providing enough information. I suggest you read the link for starters.

Ron