From: lfsheldon@gmail.com   
      
   On 1/17/2016 17:19, Stephen Sprunk wrote:   
   > On 15-Jan-16 18:18, Clark F Morris wrote:   
   >> Stephen Sprunk  wrote:   
   >>> On 14-Jan-16 17:10, Clark F Morris wrote:   
   >>>> 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.   
   >   
   > Does frequency matter when it's just going straight into a rectifier?   
   >   
   > I scanned ,   
   > but I'm not seeing anything that seems relevant.   
      
      
   I am not a credentialed engineer, but I think the main issue is in   
   transformers--a lot more iron is required for the lower frequencies--so   
   a high-frequency in a low-frequency plant is possible, I think, while   
   the reverse is not.   
      
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