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#179233 - 07/02/08 09:26 AM 2 phase services
junkcollector Offline
Member
Registered: 04/15/07
Posts: 36
Loc: Central MN
This topic has probably been brought up here before, but through some searching I found nothing. (Sorry if I'm beating a dead horse sleep )

My question is, has anyone worked in a building that had 2 phase power? Was it POCO supplied, if so, could you explain the transformer hookup? (If overhead) What kind of disconnects / panelboards where used? I seen a few pictures of a smaller 2 phase service on a home inspector site. I consisted of 2 FPE panelboards, both feed with 2 hots and shared a nuetral. The meter said 2 phase, 5 wire. It had 5 wires for a utility drop. (Pics didn't show transformer hookup)

Just wondering if anyone had any information or examples on what a service consisted of. I know this is pretty much an obsolete system, but may well still exist in larger cities so it would be interesting to know how modern components, panelboards, etc are connected. I have seen diagrams and schematics for a Scott-T connection, and the theoretical aspects of changing 3 phase to 2 phase make sense, I was more or less wondering about the physical aspects.

Thanks everyone for any tidbits you can provide. smile
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#179242 - 07/02/08 06:30 PM Re: 2 phase services [Re: junkcollector]
JBD Offline
Member
Registered: 07/12/01
Posts: 599
Loc: WI, USA
I have seen diagrams in literature from Cooper Power Systems and in Ugly's book.

The common conductor needs to be sized very carefully. On a standard 2-phase 3-wire circuit the common conductor needs to be 1.414x the line conductors.
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#179255 - 07/03/08 12:18 PM Re: 2 phase services [Re: JBD]
RODALCO Offline
Member
Registered: 12/08/05
Posts: 854
Loc: Titirangi, Akld, New Zealand
The meter 2 phase 5 wire has the following terminals.

Phase 1 line
Phase 1 load
Phase 2 line
Phase 2 load
Neutral

so 5 wires are used.
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#179305 - 07/05/08 06:27 PM Re: 2 phase services [Re: RODALCO]
JBD Offline
Member
Registered: 07/12/01
Posts: 599
Loc: WI, USA
Originally Posted By RODALCO
The meter 2 phase 5 wire has the following terminals.

Phase 1 line
Phase 1 load
Phase 2 line
Phase 2 load
Neutral

so 5 wires are used.


A 2-phase 5-wire system is basically (2) 3-wire systems, loads were never connected between Phase 1 and Phase 2.
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