Posted on 02/01/2013 7:21:28 PM PST by fatima
Four people were hospitalized with minor injuries Friday night after an explosion on a bridge over the train tracks at 30th and Cecil B. Moore in Brewerytown.
The explosion was originally thought to have been an explosive device, but after an extensive investigation, police are calling it a "thermic event."
(Excerpt) Read more at nbcphiladelphia.com ...
16 , 17 Hz. Whatever it takes.
16, 17 Hz. What Difference Does It Make????
A “thermic event”
Must have been written by the same government weenie who brought us:
“overseas contingency operations”
“kinetic actions”
“affordable health care”
“man-caused disaster”
DC I understand. 50/60 Hz I understand. 400 Hz I understand.
I don’t “get” 16 Hz. I even think the 25 Hz used in some parts of the world is too low. Visual flicker on the lights, unnecessarily large transformers, etc.
16 Hz? Why would they do that???
You would need to talk to the guys who electrified that stretch of the Pennsylvania Railroad’s Northeast Corridor in 1933. It made sense to the electrical engineers of the time. It probably doesn’t now.
Disco all the time.
Sounds like some old motor generator set that’s older than dirt, and maybe older trains needed (need?) the low frequency to run special slow synchronous motors. Just a guess... today, if trains can deal with multiple frequencies, it would of course make sense to tie it directly into the utility with transformers and have it be 60 Hz.
They probably wiring in heaven now... I would guess it was a need of synchronous motors on the trains of the time. The capability of rectifying the currents required to move a train had to wait for the era of silicon semiconductors.
Heck of a thing for epileptics
Correct, I’m sure. In the old days, there was a locomotive change at the Pennsylvania Station in New York, and not just because the New Haven took over from the Pennsy. The New Haven’s 1906 electrification was set to a different frequency.
Sorry, my misinterpretation of the story. I figured that below the roadway meant 3rd rail.
I was thinking of the old DC trolleys when I was a kid. Underground 3rd rail in town, but they did go to overhead catenary once out of the built up areas, like the run to Glen Echo.
When the DC system was built in the late 19th Century, Congress mandated that the trol;eys use third rail within an underground conduit within the District. They went to caternary wire outside the District.
The former Pennsylvania Railroad section of the Northeast Corridor is electrified with 11,000 volt 25 Hz, as are the former Reading commuter lines. I need to check the historical basis for the lower frequency. Apparently it was a combination of transmission losses, and being able to operate “universl motors” that could operate on DC.
The 17 Hz is actually 16 2/3 Hz of the Deutsche Bahn (1/3 of 50 Hz).
Those are old legacy systems
In 1997, I read Michael Bezilla's The Electrification of the Pennsylvania Railroad, and now it's out of print. I was going from a failing memory.
The old New Haven was also at 25 Hz. There used to be a locomotive change at Manhattan Transfer (not far from the current PATH Harrison station), however, the original Pennsy New York electrification was third rail (600 vdc) from Sunnyside Yard to Manhattan Transfer in order to enable tunnel operation under the Hudson and East Rivers. When the PRR extended the 11kV catenary from Trenton to New York, Manhattan Transfer was eventually done away with.
Now the former New Haven line is 12.5kV 60 Hz to New Haven (formerly 11kV 25 Hz, the old NH power system was badly worn), with the new Amtrak electrification from New Haven to Boston at 25kV 60Hz.
Thanks!
Great info.
Thanks for bringing me up to speed. I was drawing a blank on the 1999 Amtrak electrification to Boston.
Anyway, the history I learned was that a most trains had standardized on large DC commutator motors, which could also be used in AC. Problem was, the higher the frequency, the more internal inductance problems you had. 25 Hz was a good compromise between internal inductive loss and transmission loss on the line.
They are a radical group called ‘Hz-bull-duh ‘!
A radical group of electrons , inconvienced , and doing self-immolation.
Thermahu Akbar !
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