ECN Forum Forums General Topics of the Trade General Discussion Area Surviving DC Power Systems

I saw a mention in a recent thread that there are still DC power systems in some of the old Chicago skyscrapers. I also saw a mention quite a few years ago that the NYC theater district still has (had?) DC power, as a holdover from the days of Edison himself. And I believe I saw a recent reference here to DC power in Los Angles or San Diego.

Can anyone confirm that such systems are still in operation? What in the world are they doing with them?--you pretty much can't buy anything for a DC system, and haven't been able to for years. (OK, a regular incandescent light bulb will still work, but you're not going to find a TV or a computer or a stereo that's designed to run on a DC system.)

http://query.nytimes.com/gst/fullpage.html?res=940CE7DF173DF93BA25750C0A9679C8B63

according to con-ed, 4400 older buildings in manhattan still use DC for elevators, water pumps, etc.. (as of 2001)

Many large factories are still buying Dc systems, especially for speed controlled motors. Also, all the devices you mentioned really run on DC after the switching ps that is

Add to the list, many older buildings in SF,CA. Mostly for elevators, but some of the surviving industrial buildings have cranes, HVAC motors, dock doors etc. There are also several rectifier buildings for MUNI for all the over-head electric for busses and trains...

What's old is new again.
There is a movement to distribute power within a datacenter as DC instead of AC. The concept is that the small power supplies in the servers/computers are sooooo inefficient, that we might as well provide the power directly from the output of the large rectifier within the UPS.

BTW: many DC applications like elevators use local rectifiers rather than getting it from the utility. The subways in NYC use 600vDC too, through rectifiers.

We provide the DC bridge feeds for the city in the same manner as traction power is provided to the 3rd rail. I can't imagine what it would be like if our incoming power was 600 VDC instead of 12.6 KVAC. It's much better to have the transformers and rectifiers closer to the load.
Joe

"Can anyone confirm that such systems are still in operation ? "

Not only are they still in operation, but plans are in the works, to expand DC projects.

Here is one example:
http://www.neptunerts.com/data/downloads/Handout%20-%20PROJECT%20OVERVIEW.pdf

My DC Motors & Control Class, would always say, on the first day of class, i am wasting my time here, but i have to take this class, as the class came to a years end, i would hear, i never knew, there was so much run by DC.

Ron, I think that is an excellent idea. Not as much to power the computers but to replace the dozens of wall warts we have in the average office or home.
I may actually be running a 12vdc line in my house for emergency lighting and such.
I think that if I am running around wet, in survival mode, after a storm I would rather be screwing with 12vdc than 120 ac.

[This message has been edited by gfretwell (edited 04-04-2006).]