From: stephen@sprunk.org   
      
   On 17-Jan-16 19:58, Clark F Morris wrote:   
   > Stephen Sprunk  wrote:   
   >> On 15-Jan-16 18:18, Clark F Morris wrote:   
   >>> 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.   
      
   Google can't find anything about that presentation aside from similar   
   claims here by you back in 2009, 2011 and 2013--and several folks (who   
   all seem more knowledgeable than I) questioning its veracity.   
      
   In particular, one said that _maybe_ it was true long ago when motors   
   ran at the catenary frequency but definitely not today because modern   
   trains put the power through a rectifier (and often an inverter) before   
   it gets to the motors.   
      
   S   
      
   --   
   Stephen Sprunk         "God does not play dice."  --Albert Einstein   
   CCIE #3723         "God is an inveterate gambler, and He throws the   
   K5SSS        dice at every possible opportunity." --Stephen Hawking   
      
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