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#31095 11/10/03 04:08 PM
Joined: Nov 2002
Posts: 169
Cleaning out old,old files and some of the items brought back memories. Are any of these systems still in use?

In about 1976, DC in buildings in downtown St. Louis.
1963-Two phase three wire in NYC.
1955-Six phase double delta in Nashville, TN.
Still have a lot of files to read before disposal.

#31096 11/10/03 06:26 PM
Joined: Aug 2001
Posts: 7,520
I'm always interested in old systems and the way things developed.

Is there anything in these files worth scanning and posting on ECN for posterity?

#31097 11/10/03 06:57 PM
Joined: Dec 2000
Posts: 4,293
I second Paul's appeal.
Please save them, maybe scan and archive them (I know I'm asking for a lot).
I wish I'd taken pics or kept records of all the things I've run across.
As I said at a friend's eulogy, "If I was to tell you the truth, you'd think I was lying, or crazy."...S

#31098 11/10/03 10:31 PM
Joined: Nov 2002
Posts: 794
Likes: 3
1963-Two phase three wire in NYC.

I had an apartment in Westchester County NY that had 120V/208V (2 of 3 phases). More recently I had another apartment (which was fairly new) also fed by 120V/208V (2 of 3 phases). It took a while for me to figure out why my experimental radios run off of 250V were underperforming until I measured line to line.

#31099 11/11/03 12:40 AM
Joined: Apr 2002
Posts: 2,527
'ise — A 1N4007 along side a 35W4? That's downright dastardly. {But absolutely brilliant!)

[This message has been edited by Bjarney (edited 11-11-2003).]

#31100 11/11/03 06:18 AM
Joined: Jan 2003
Posts: 4,391

What you had was single phase (two phases of a 3 phase system), not a two phase system.

I believe rowdyrudy is talking about an old system called two phase.

We still install 208/120 3 phase services in multi unit dwellings and feed the units "single phase", Two hots, neutral and ground.

I have never run across anything but single or three phase systems.

Bob Badger
Construction & Maintenance Electrician
#31101 11/11/03 06:55 AM
Joined: Sep 2003
Posts: 650
If you have two hots and a neutral of a three phase system, then you do have two separate phases available.

A load connected between any two conductors of a three phase system sees a single phase, but as soon as you have three conductors (any three, including the possibility of two hots and the neutral) then you have different available circuits with different phase angles available.

You are correct, though, that this is different from the 'two phase' systems that were used in the past. In a 'two phase' system you have two separate circuits where the phasing difference is 90 degrees rather than the 120 degrees found in 3 phase systems.

Thread hijack going to new odd systems: EPRI has done research on using 12 and 18 phase systems for power transmission. For a given phase to neutral voltage, the phase to phase voltage goes down as the number of phases goes up. (I can give you the math, but imagine a circle. The radius of the circle is proportional to the phase to neutral voltage. Now draw a set of equally spaced dots around the circle, one for each phase. The distance between the dots represents the phase to phase voltage.) Because the phase to phase voltage goes down, the required phase to phase spacing goes down. The spacing from the conductors to the tower and ground remains the same, but you can pack more conductors into the same right of way, and thus carry more total power.


#31102 11/11/03 06:57 AM
Joined: Sep 2003
Posts: 650
P.S. I second the call to scanning in some files on the old systems. It's really great to see where modern systems come from.


#31103 11/11/03 11:10 AM
Joined: Jul 2003
Posts: 141

Are you sure the two phase system is 90 degrees different and not 180? Not that I know...just asking.

#31104 11/11/03 11:40 AM
Joined: Sep 2002
Posts: 1,498
Likes: 1
C-H Offline
The two phase system is indeed 90 degrees. It was essentially two single phase systems mounted 90 degrees apart. Not very useful apart from starting motors.

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