3 phase transformer transformer manufacturer step down transformer 3 PHASE TRANSFORMER Dyco Electronics manufactures custom surface & PCB mount,MIL-PRF-27, XFMR, toroid, control, 60 HZ, flyback, audio, switching, swinging, chokes, auto, and 3 phase transformer products. A 3 phase transformer is found in most large power - and small - transformer installations which provide all 3 phases. Sometimes they do so with three single-phase unit, sometimes with one 3 phase transformer unit. In either case, there are six windings, three on the primary and three on the secondary side.