Naturally since the system will be integrated with the Orange Line, this is necessary. I wonder what sort of propulsion would be appropriate for a dedicated, heavy-rail line of 23 miles with 18 stations that didn't have to account for any old system? I say overhead AC to avoid the cost of acquiring land and utility for all of those substations. I wonder about acceleration between stations, too.
To be fair, they truck these prefabricated structures in and build walls around them. I also wonder about power consumption and loss as we go AC-DC-AC.
all these arguments about the power source ignores the fact almost all traction motors are now beiing buit AC. AMTRAK certainly will not be buying any more DC and the class 1s are very close. Any light rail / streetcar that is now being built north of N 40 appears to be all AC traction. I m sure there are exceptions. With AC traction the problems of snow, ice, sand grounding out DC motors is eliminated. as other posters have nooted there is somewhat more electronics with AC transmission but if AC traction is used anyway ??????
When building a new line, many considerations are brought to bear on power distribution selection. If subways and tunnels predominate, catenary may require large tunnels for clearances. Third rail power with frequent substations might be expensive because of the cost of realestate. The question of frieght service and possible fowling of third rail by unusual freight equipment might be considered.
The Chicago Transit Authority continues with 600VDC third-rail for distribution but has converted to AC traction with the 5000-series cars now being delivered. Subsequent orders now in the proposal stage will continue with AC traction.
blue streak 1 as other posters have nooted there is somewhat more electronics with AC transmission but if AC traction is used anyway ??????
as other posters have nooted there is somewhat more electronics with AC transmission but if AC traction is used anyway ??????
Keep in mind that almost all of the drive electronics for AC traction motors run off of a DC bus. There are circuits called cycloconverters that will convert AC to any frequency from zero to one third of the line frequency, but for anything but a fractional horsepower motor, you will want to run it off a three phase line.
- Erik
The RER in Paris uses overhead electrification as does the Tyne and Wear metro in the UK. The Budapest metro line one does too, but it basically was a street car line that was put underground in the 1880's. Septa's centre city commuter tunnel in Philly has catenary, but of course it's the former Penn and Reading suburban lines. There is a phase break in the tunnel as the 2 systems used different voltage. In know the Pennsy side is the same as Amtrak at 12.5 kv, can't remember what the Reading side uses.
drewhcan't remember what the Reading side uses.
Was the 'same' 11kV that the old PRR electrification used. Probably no point in increasing it (no long heavy trains coexisting with very fast trains).
If I remember correctly, back in '76 when 4800 was pulling the Reading MUs to Trenton, the 'issue' about their not going under their own power was one of signaling and control, not overhead voltage. At least one pan in the train was up for lighting and heat.
RME
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