stuart hath wroth:

If I have a 600w inverter, cpable of 1200w maximum, and I have a 20
metre extension lead from it to run a 500 watt angle grinder (disc
cutter), will this be okay or does the extension lead mean I need a
higgh rated inverter?

That depends on whether your 600 watt inverter can deliver 500 watts
at 100% continuous duty cycle. Most of the cheap mobile 12VDC
inverters cannot and will get toasty hot. If it's a tiny little
portable inverter, it's gonna blow. If it's a big ugly heavy
monsterious huge monster, with oversized heat sinks, and a noisy fan,
it will work just fine.

There's a small chance that the extension cord may be a problem. If
it's of insufficient wire guage, the voltage drop will be excessive
and your grinder will run slow or grind without much torque. Just
about anything bigger than #16 awg will work, but there's always
someone that wants to use a roll of zip cord as a long extension cord.
What's the wire guage?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558