Transformer Wiring for Triple Phase to Split Phase Conversion

[chopficaro]

how are the wires wrapped on a transformer that converts from triple phase power distribution to split phase outlets?

 

[dlgoff]

how are the wires wrapped on a transformer that converts from triple phase power distribution to split phase outlets?

All you need is one phase to make a split phase.

http://en.wikipedia.org/wiki/Split-phase_electric_power"

 

[chopficaro]

yes, but it must be BALANCED, how would they maintain balance if all the loads are not equally shared on all 3 phases?

 

[dlgoff]

This is in my opinion since I don't have first hand information as to how, since it would depend on how the supplier operates their business, but... When they install residential transformers in a city or in rural areas where it is easier to string one wire, the power company would wire the areas according so a plan so to maintain a phase balance. Power is transmitted from power generation station to large substations that then ship the power to distribution substations. Here at the distribution point is where you would need watch. So depending on the situation, when unbalance occurs you may be able to switch some of the load around. If all three phases are available at the pole, it would be a simple matter to switch the wiring to a different phase.

 

[russ_watters]

Power distribution is always 3 phase and it is converted to single phase locally. Pole mounted transformers you see outside some neighborhoods are where it is done:

Outside a typical house you can see a pole mounted transformer mounted on the electricity pole. It's a step-down transformer used to convert the high voltage (7200 or 14400 volts) down to the standard 120/240 volts used in the home. The high voltage distribution lines (7200 or 14400 volts in the US) attach to the two bushings on top. The low voltage wires (two hot wires and one neutral) attach to the three terminals on the side. The secondary winding is center-tapped and grounded, making the two end conductors "hot" with respect to the center tap. These wires run down to the electric meter and breaker panel inside the building. Connecting a load between either hot wire and the neutral gives 120 volts. Connecting between both hot wires gives 240 volts. This is the setup for single-phase electric power in the United States. If three-phase power, three pole mounted transformers of the appropriate KVA rating are wired in either a wye or delta transformer bank.

http://www.powertransformer.us/polemountedtransformers.htm

 

[chopficaro]

tyvm, very informative, this has been bothering me for some time

 

[dlgoff]

Just a quick note. In the rural area where I live for example, there are only two conductor strung between the poles that service many square miles. So that means that to balance the transformer loads on their "distribution" substation, moving loads to a different phase would be impossible without building a new line. Unless there are several lines by design coming from each phase to start with that could be switched at the station, which I think is very unlikely.

 

[sophiecentaur]

I think they work on the statistics of large numbers. If they share out the phases between equal numbers of similar consumers then the demand will balance out 'near enough'. In the UK, they tend to have a single, three phase, transformer which has sets of three single phase (plus neutral) pairs, radiating out along the streets in a locality. The phases tee off to each house, in turn,so each house gets a phase different from its two neighbours. Of course, we use 230V supply for everything so we do not need a special split phase supply for heavy domestic loads. A 100A fuse is about the maximum you will ever (?) find in a domestic situation.
I imagine the average length of supply line is much shorter in the UK than in the US - There are more remote dwellings in the US and even the cities in the US (with a few exceptions) have more space between dwellings.