hi to all, thanks to audioguru for all the answers. They're all enlightening. I'm not much into electronics, but I'm collecting topics on alternative energy sources - wind, solar, etc. Part of my collection are plans for 5,000W inverter which I downloaded from the internet. Sorry I can't share it here because it's not my property, but I'll send them to Ronnie. (Also, they're not purely electronics devices) I haven't tried building any of them yet. Perhaps Ronnie could go over the plans, do some modifications and publish them. Thanks a lot to all you great guys !