I was looking at a table that lists full load ratings for 3-phase transformer banks and ran across a 30kva, 3-phase, 120V listing. . . started talking about it with others and the debate is whether or not the only way to attain this 3-phase voltage is by a delta bank or by some other configuration. I have never heard of any one ever needing this.
A 120 volt delta will distribute a heavy 120 volt single phase load on a three phase system better than a simple single phase connection will. With unity power factor one transformer all transformers will have equal current. However, because of phase angle differences, one transformer will supply half the energy and the other two will supply the other half of the energy.
Generators are often converted from three phase to single phase with a "Double delta" connection. The six windings are arranged into two 120 volt deltas. Each delta provides 120 volts single phase. The two deltas together provide 120/240 volts single phase.
respectfully
