From: cfmpublic@ns.sympatico.ca   
      
   On Sun, 17 Jan 2016 17:19:20 -0600, 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?   
      
   It does according to an engineer I heard give a presentation to the   
   Electric Railroaders Association, New York Division over 25 years ago.   
   It has to do with how much power can be transmitted and at 25 cycles   
   for given voltage more power can be transmitted than at 60 cycles.   
   Thus 25 KV is needed to transmit the same power at 60 cycles as is   
   transmitted by 12 KV at 25 cycles.  I have seen it discussed but also   
   can't find where and I don't have the time to dig up the ERA   
   presentation.  I think his name was Harry Rappaport but its been a few   
   years since I last looked at the presentation.   
      
   Clark Morris   
   >   
   >I scanned ,   
   >but I'm not seeing anything that seems relevant.   
   >   
   >S   
      
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