| Thanks everybody for your replies.
| I am from an Asian country where electricity is scarce.
| So when farmers' require electricity for agricultural activities, the
| Electricity supply agencies disconnect one phase, from distribution
| of electrical lines which go to factories so that they can not use
| One of my friend wanted to run a 3 phase furnace (the furnace works on
| and current consumption is 55 Amps.). He asked me the question, which
| I posted on forum.
I assume you meant 230 volts.
| BTW The following link mention about
| "Scott T connection of transformers is a method used for changing 3
| phase to 2 phase or vice versa.
| There is no mention of a neutral wire here. Just "3 phase to 2 phase
| or vice versa".
| Can this type of transformer(s) solve our problem?
The voltage between any two phases, compared to the voltage between
the remaining third phase and neutral, in a wye/star system, is 90
degrees apart. Two transformers with the appropriate voltages can
be used to produce three phase at another voltage this way. Ratings
are reduced somewhat, but it works, and many transformer sets are
built this way. But you need all 4 wires to do it. That is what
a "Scott T" connection is. The vector diagram looks like a "T".
Your problem can be solved with two transformers in a different
configuration as my previous post described.
| We have "wye" system and do have a neutral wire, which is not
| " I am very sorry for not mentioning it earlier."
I suspected that. Often the neutral is there and is not counted by
many people. Motors designed for delta configurations do work on
wye configurations and do not need to be connected to the neutral.
Outside of the North American region, delta is much less common as
a power configuration.
Delta would also cause problems if just one phase were disconnected.
The two working phases would energize the disconnected line. This
does not happen with wye.
| Because of some reason my mind was fixed on the words of my friend
| i.e. " 2 to 3 phase" which he used when he asked me the question.
When one looks at the vector diagrams for center-tapped single phase
such as used in North America, and then wye (or star) three phase, it
really makes one think that single phase could be called two phase.
There are indeed two vectors from "zero". They just happen to be at
180 degress, and thus can be wound on the same core as the other, or
just be one winding with a center tap. So that's why it is usually
just called single phase (you can't derive any more phases from it
whichever way you call it).
But if you have 2 phase angles that are 120 degrees apart, with the
neutral in between, then you can derive the missing 3rd phase using
a pair of transformers like I described in my previous post in this
| When so many experts are here to answer I want to take liberty of
| asking another question which is related to this topic. Can we create
| neutral of "wye" system again at our end if it is disconnected by
| electricity supply agencies assuming the all the 3 phases are present?
Yes, a neutral can be created from the 3 original phases. There is a
transformer specifically designed for doing this called a "zig-zag".
Variations on that transformer also do other things, so you have to be
specific. The design of it is a bit complex, but it is sufficiently
common that many transformer manufacturers market complete units for