From: stephen@sprunk.org   
      
   On 18-Jan-16 20:06, Stephen Sprunk wrote:   
   > On 17-Jan-16 19:58, Clark F Morris wrote:   
   >> 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.   
      
   After a bit more (re)reading, the issue was that doubling frequency   
   squares the power factor; however, modern trains are so close to unity   
   (due to better rectifiers) that it's effectively irrelevant now.   
      
   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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