From: stephen@sprunk.org   
      
   On 15-Feb-16 12:56, Clark F Morris wrote:   
   > Stephen Sprunk  wrote:   
   >> On 15-Feb-16 07:50, 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?   
   >>   
   >> As written, yes, but it requires twice the current, which means   
   >> even more power pulled from the grid but lost to resistance rather   
   >> than delivered to the trains.  That's not good.   
   >>   
   >> If you actually meant 2x12.5kV and/or 2x25kV, that ratio may   
   >> change.   
   >   
   > The reason I am pursuing this is that the latest M8 Metro-North EMUs   
   > only work on 60 Hz (and 3rd rail DC).  Thus in order to get them to   
   > Penn Station and beyond the Amtrak line at least from Sunnyside   
   > south and west would have to be converted to 60 Hz, either at 12.5KV   
   > or 25 KV in order to use the M8s on NJT.   
      
   I'd hope they'd actually go to 2x12.5kV or 2x25kV to reduce currents,   
   but that's mean running extra cables through the tunnels and possibly   
   autotransformers under the river, so it's not a given.   
      
   > Given the tight clearances in the tunnels, 25 KV may be virtually   
   > impossible to implement.   
      
   Research overseas shows that railroads vastly overestimated required   
   clearances in the past, in part because they didn't take frequency into   
   account; (2x)25kV 60Hz may be safe at the clearance PRR _thought_ they   
   needed for 11kV 25Hz.  Or maybe not.   
      
   > Hence the interest on what the performance implications of changing   
   > from 25 Hz to 60 Hz.   
      
   None for modern trains, aside from potential clearance reduction to   
   allow a higher voltage (and thus lower current and/or higher power).   
      
   > So far as I know, all NJT equipment currently in operation can run   
   > under 12.5 Kv, 25 or 60 Hz and 25 KV 60 Hz as can all Amtrak   
   > equipment.   
      
   True for Amtrak.  All NJT equipment is frequency-agile, so moving to   
   60Hz is fine, but I'm not certain that all of it is voltage-agile; if   
   not, NYPenn and environs must stay at 12.5kV (or 2x12.5kV).   
      
   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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