minimum input to an inverter

Your 600VA inverter will require some 56 amp from a 12 V power supply - as an average. My guess is that your 12 V dc power supply has to be able to provide that kind of current with the overcurrent protection set somewhere higher that 60 amp. I bet that a large battery would be more economical than such power supply.

THANX INDEL, well we are using some conventional energy resources so thats why we have kept battery aside, one thing you can help me out with is that can i convert 3 ampere to 30 ampere usuable current values using darlington amplifier or any other method you suggest or IS IT NOT POSSIBLE

Well hw cn u say i dont know about electricity ? i agree may be i don't know as much as you bt as a student of electronics i can guess you haven't performed any such experiment yourself. . . . .any ways thanks INDEL . . . . . and yup money is honey :-)

Indel has kindly taken the time and trouble to write a very lucid explanation....
The fact that you needed the explanation proves his assertion that you don't know much about electricity.

It can be dangerous to think you understand more than you actually do.
Del

the guest post is by me. . . .i 4gt to re-login. :)

That is true in linear mode but not in switching mode.

You can increase the current at the output IF you have a higher input voltage. In this case, you need at least 30VDC at 30A to produce the 56A DC at 12V. Using a step-down switcher configuration, you will get the equivalent of a high frequency step-down transformer. All you need is a power transistor and heatsink, an inductor and a control circuit.

This is not a simple circuit and you will needs some expert's help if you go ahead with it. Find a local engineer with power electronics knowhow.

If your source is already AC, simply use a step-down transformer + rectifier.

THANX GURU for proving that i don't know much, if i have known that much i mìght have solved my problem myself rather than asking on the forum. I DON'T HAVE KINDA RESOURCES TO PERFORM EVERY EXPERIMENT SO IF YOU CAN HELP ME PLEASE PROCEED.

I think we have a language/communication problem.
So forgive me if I state something which you may already know.

If your power souce can only supply say 3 amps...
(E.G you connect a current meter from the + to the - terminal and it reads 3 amps)
There is no way you can increase this current, it's as simple as that.
You could add more power souces in parallell so two power sources give 6 amps, three give 9 etc.
As an example, a PP3 battery when new will give say 9volts off load and a short circuit current of say 1amp (I'm guessing here) limited by it's internal resistance... You can do nothing to increase the 1 amp figure, although I s'pose you could place it in liquid Nitrogen, that might help a little.
But no ammount of circuitry or experimentation will increase the current capability.
And yes we have all tried it, I'm sure we've had situations where the ultimate limiting factor of our circuit was the power supply.
You are quite right to experiment yourself and discover these things...but once you have discovered them, then accept them and start learning more...don't waste your efforts trying to change the fundamentals laws, they are fixed.
Del

thanks guru. . . . .

The only way to make 30A DC at Uout out of 3 A DC at Uin is to take a DCDC-Converter. But, assumed your converter has an efficiency of about 90%, the output voltage Uout will be only somewhat like 1/11 Uin.

UWEKA thanks . . . . i havn't given a second thought to converters rather i was stuck to amplifiers. . . . but due to so much confusion now i have to perform expt. myself. . . .

shocked at the ignorance level. fundamental laws have been forgotten and also forgetting to show courtesy of being in communication with experts.

this guest getting crazy . . . . lol :-) . . .well no 1 is expert may be one knows more than other. . . .