You are referring to a Scott connected configuration, in which a 3 phase primary is connected to two transformers in such a manner that 2 phase power is availableon the secondary. This information is available in McGraw-Hill's "American Electricians Handbook"
Designed to replace the Edison 3 wire DC hook up when swapped over to AC. Unless you work around coal mines (DC equipment runs on AC or batteries) you'll never see one. coal mine info is old, don't know if they still do it that way.
Re: crazy 3 phasy#127561 08/30/0105:34 AM08/30/0105:34 AM
According to my engineering books the Scott connection is normally used for 2-phase to 3-phase conversion. If used in a 3 to 2 conversion the transformer output needs to be reduced to 86.6% of the combined single-phase ratings.