On Friday, 15 January 2016 20:26:59 UTC+1, Stephen Sprunk  wrote:   
   > On 14-Jan-16 17:10, Clark F Morris wrote:   
   > > Stephen Sprunk  wrote:   
   > >> On 11-Jan-16 00:50, Michael Moroney wrote:   
   > >>> They really aren't completely independent.  Converting to 2x25kV   
   > >>> as the first step would require 25kV 25Hz transformers and   
   > >>> equipment, only to be replaced by 60Hz on the next step.  If   
   > >>> combined, one entire set of equipment could be skipped.   
   > >>    
   > >> 25Hz transformers can handle 60Hz.  It'd be simplest to go to   
   > >> 12.5kV 60Hz first, which wouldn't require _any_ new equipment, a   
   > >> few phase breaks at most.  (That assumes all 25Hz-oly wayside   
   > >> equipment has been replaced with 25/60Hz equipment, which Amtrak   
   > >> has been doing as the former fails since at least the 1980s.)   
   > >    
   > > Except as I understand it, 12.5 KV won't give enough power to   
   > > support 100+ mile an hour operation.  Note the relatively slow speeds   
   > > on the Metro-North New Haven line.   
   >    
   > Amtrak (and its predecessors) have been doing up to 135mph on 11kV 25Hz   
   > lines for around a century; the main reason they couldn't go faster was   
   > the variable-tension catenary.  That's roughly twice as much current as   
   > 200mph on 2x25kV lines in France and China, so I'm not sure current is   
   > really a limiting factor.   
      
   I doubt that 11 kV is going to impose significant limits on power due to   
   current draw: in Germany ICEs run at 200 mph (320 km/h) under 15 kV, and on   
   classic lines in France and the Netherlands trains run at 100 mph (160 km/h)   
   under 1500 V DC.  There are    
   even trains in the UK running at 100 mph on 750 V DC 3rd rail (although a 3rd   
   rail has a larger cross section so can almost certainly cope with more current   
   than OHL).   
      
   Robin   
      
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