From: cfmpublic@ns.sympatico.ca   
      
   On Fri, 15 Jan 2016 13:26:57 -0600, 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 should have been more clear.  I meant 12.5 KV at 60 cycles.  I seem   
   to recall the problem has to do with back EMF but my memory is vague.   
      
   Clark Morris   
   >   
   >S   
      
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