three phase transformer

[kolani]

A three phase transformer is constructed by winding three single phase transformers on a single core. These transformers are put into an enclosure which is then filled with dielectric oil. Now, if we construct a three phase transformer from three single phase transformers, but not on single core, and then put them into an enclosure, what would be drawback of this design vs. the first, single core design?

 

[jim dungar]

Re: three phase transformer

Off the top of my head;
The resulting core asembly would be bigger and the magnetic leakage flux would need tighter controlling.

That being said this is a common design (at least one POCO in my area requires it) and is usually called a TRI-PLEX core.

 

[jim dungar]

Re: three phase transformer

In answer to your private message, as I have already stated, a big disadvantage is the increased steel in the core resulting in an increased in the size tank and the requirement for more oil. Also, because there is no common magnetic path for the flux in the two outside cores, care needs to exercised to reduce the amount of flux that will want to travel throught the transformer case.

The primary advantage to this design is the reductio in ferroresonant problems associated with common core wye transformers during single phase fault conditions.

The actual formulae are not my area of expertise anymore.