[GreenKeys] NYC subway power

[Peter Gottlieb]

Fascinating.  I worked in the city for many years, commuting in via Metro North from Westchester.  I still remember the generation plant in Yonkers with their big generators which you could see spinning in the summer when they had the huge doors and windows open.  I also remember the old stations with the flickering 25 Hz bulbs where they used 5 120 volt lamps in series, like Christmas lights.  One burned out and a whole bunch went out.  Glad to be out of that rat race and back to real engineering.

Peter



Aug 10, 2011 05:24:06 PM, nagle at animats.com wrote:

On 8/10/2011 1:30 PM, greenkeys-request at mailman.qth.net wrote:
> Bruce Gentry wrote:
>>> Larry Tighe wrote:

>>> The subway AC distribution was 25 cycles, and the bulbs did
>>> flicker quite noticably. They were indeed left hand thread, and
>>> in groups of 5 wired in series for 600 volts. If the AC power
>>> failed, the station master could switch them to take service from
>>> the third rail at 600 volts DC.  I think all of them are gone
>>> now, but they were there in 1992.

     Assuming anybody cares,

Yes, the BMT and IRT parts of the NYC subway system were once 25Hz.
Distribution was 11KV, 3 phase, and was converted to 600VDC traction
power at AC to DC substations using rotary converters, later huge
mercury arc rectifiers, and finally solid state diodes.  Unusually,
3-phase power was converted to 6-phase power in special transformers
before rectifying, to reduce ripple, and hence unwanted vibration in
the DC traction motors.  The original generators ran at only 75RPM,
driven by reciprocating steam engines with a 42-inch piston and a
60-inch stroke. Each engine drove a 5 MW generator, and there
were 11 engines in the original 1904 plant.

In 1915, there was an upgrade to turbines, with 30MW per turbine.

The power house building still stands, at 59th St. and 11th Av,
an impressive, ornate building. Con Ed currently owns it and
does some steam generation there, but no electricity is generated.

NYC subway traction power is still 600VDC, but the AC system is
all 60Hz now.

The original system is well documented:

http://www.nycsubway.org/articles/powerplant.html

The AMTRAK northeast corridor is still 25Hz.

     John Nagle


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