Pls kindly help me with calculations on the wire gauge, and no of turns for a 1.5kva ,20A inverter ,P1=230v,P2=12v also the gauge and no of turns for P1= 220 P2=15v ,5A .thanks
I do not see how your calculations work. Also you have not specified waveform or frequency.
Look up 'ludens transformer', he gives details of flux density in the core and current density in the wire. There is a good exposition on how to wind the transformer.