From: Jan Steinman via EV <[email protected]> >> In summary a solid state transformer is less efficient
> I'm certain this is not true, even on a Pin vs Pout basis, and certainly > not on a size or weight basis. > > Eddy-current losses and I2R losses are greater the lower the frequency. > By choosing the frequency and the ferroresonant components carefully, > one can easily get 10x the efficiency. > > To verify, find an old, heavy "wall wart" 60Hz transformer. Plug it in > for an hour or so. Feel it. It's warm! Even with no load. Eddy current losses go UP with frequency. I2R losses don't correlate well to frequency. Higher frequencies reduce the wire length; but "skin effect" reduces the effectiveness of the wire (the higher the frequency, the shallower the current will penetrate into the surface of a conductor). Transformer performance is mainly determined by the design tradeoffs. What did the designer care about? Size, weight, cost, efficiency? You can optimize for any of these at any frequency. The efficiency of a dirt-cheap near-junk quality transformer is truly bad. Many of these have so little iron and such thin wire that the resistance of the winding is what limits the current; not the inductance. Compare this to a quality 60Hz transformer. These routinely have efficiencies in excess of 95%, and can be as high as 99% if optimized for efficiency. The main drawback of 60Hz transformers is not efficiency; it's size and weight. -- Excellence does not require perfection. -- Henry James -- Lee A. Hart http://www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
