On 06/26/2011 05:55 PM, Jussi Peltola wrote: > On Sun, Jun 26, 2011 at 11:36:24PM +0200, Ingo Flaschberger wrote: >> but transforming is not easy. >> ac/ac transformers are easy tu build and very immune against lightning >> strikes - inverter systems are not. > Switching DC is also problematic since there is no zero crossing to > extinguish the arc.
Sometime look at break ratings for AC and DC breakers and compare the relative sizes. Shows this effect. Easy answer is: don't use mechanical switches for routine switching... (easy if there is an inverter present, like in a VF drive or switching power supply). Big enough AC breakers maintain the arc over more than one cycle so have this problem too. (plasma quench time at atmospheric pressure can be a while...) Given the technology of the time, AC won rightfully. Still better for most distribution. -- Pete