Confused ME

[schick]

Please help the electrically simple minded (aka mechanical)

3 phase 240v power...
has 2 conductors.

how do I siphon off 120v regular electricity?
Does 3 phase consist of 2 conductors carrying 120v and one common return line??

Help!! I'm getting more and more confused the more I look at this and try to figure it out.

Any and all responses EXTREMELY appreciated!

schick

 

[dpc]

First, I think you are talking about 120/240V single-phase, not three-phase 240V. A three-phase 240V supply would have to have three phase conductors, not two.

The typical residential service (in the U.S.) is 120/240V single phase. There are three wires brought in from the utility. One of the three is a neutral/ground wire. The other two are "hot" wires. The voltage across the two "hot" wires is 240V. The voltage from **either** hot wire to the third (neutral/ground) wire is 120V.

HTH

 

[busbar]

A 3ø source has at least 3 wires. To serve a 1ø 120V load, the simplest way is probably with a 1ø transformer connected to two of three wires.

 

[KAA]

Hi
May be this would be helpful
Your Supply is probably 240 Phase to Phase (basically 2 wires) tapped from a 3 phase source. (I have seen at some locations where 240 V Phase to Phase is generated for specific use to avoid neutral. I presume it may be the same)

You may have to provide transformer to reduce the voltage to 120V but check the voltage across the two wires before proceeding.

 

[Outback]

240v 3Phase is a Delta connection which has a power leg.
There are 2 conductors which measure 120v phase-ground and 240v phase-phase, the power leg will measure 208v phase-ground. You can split off a 120v single phase supply by tapping one of the 120v lines and provide a continuous neutral.

 

[jbartos]

Suggestion: The Utility normally installs two overhead transformers in open-delta connection forming the following System Voltage:
Overhead Transformer No. 1:
240V -------------- center tap --------------240V
(No.1 conductor)---(No.2 conductor)---(No.3 conductor)
(120V between each hot conductor 240V and neutral=center tap of one overhead (pole) transformer)
Overhead Transformer No. 2:
240V -------------- center tap --------------240V
(No.4 conductor)---(No.5 conductor)---(No.3 conductor)
(120V between each hot conductor 240V and neutral=center tap of one overhead (pole) transformer)
Remarks:
1. No. 5 conductor may or may not be used in the distribution. It depends.
2. No. 3 conductor of Transformer No. 1 is connected to No. 3 conductor of Transformer No. 2 forming "open delta" three phase, 4-wire system (if conductor No. 5 is not used). It is 240/120V open delta, 3phase, 4wire system.
If conductor No. 5 is used, one obtains 240/120V, 3phase, 5wire system. Average house is usually serviced from one transformer with 240/120V, 1phase, 3wire system.