From: Sam.Wilson@ed.ac.uk   
      
   In article <85ebcb0f-1ce3-45f1-b9ce-288d1be23434@googlegroups.com>,   
    rcp27g@gmail.com wrote:   
      
   > On Monday, 15 February 2016 14:53:19 UTC+1, Clark F Morris  wrote:   
   >   
   > > Can as much power be transmitted from the grid to the locomotives /   
   > > EMUs at 12.5 KV as is delivered at 25 KV at a given frequency?   
   >   
   > Yes.  It is possible to design equipment that will get the job done.   
   >   
   > > If not does lowering the frequency change the amount of power that   
   > > can be delivered assuming modern equipment in all cases?   
   >   
   > A lower frequency will mean larger, heavier, more expensive equipment   
   > (primarily the main transformer).  The reason I've been banging on about   
   > German kit is that they use an even lower frequency (16.7 Hz), so need an   
   > even larger and heavier transformer than 25 Hz demands.  In spite of this,   
   > they can get the job done.   
   >   
   > The real issue is that for lower voltage (12.5 kV as against 25 kV) and lower   
   > frequnecy (25 Hz against 60 Hz), you need more, larger and specialist (ie not   
   > off-the-shelf) hardware, so getting the job done is significantly more   
   > expensive.  If you have a large network already running on the legacy system,   
   > it doesn't make economic sense to change it (hence the German/Swiss/Austrian   
   > networks remain at their absurdly low frequency), but for the much smaller   
   > network in the US, it makes more sense to work to eliminate the low frequency   
   > sections to reduce long-term costs.   
      
   Excuse me for butting in, but the section of the Wikipedia page at [1]   
   seems to cover most of these issues tolerably well.   
      
   Sam   
      
   [1]   
      
      
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