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.   
      
   Robin   
      
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