South eastern equipment company offer power-o-stat continuously adjustable voltage auto transformers. It deliver voltage from 0 to 270 v in single-phase and 0 to 470 v in three-phase continuously without any break in outptu voltage. This variation is obtained by turning the knob in less than a complete circle rotation. Salient features include that these units are very compact and very economical compared to conventional transformers. The constructions of these units are in toroidal form. Cold rolled grain oriented silicon steel sheets are used to form the toroidal core, which will have minimum electrical losses. The end forms on which the single layer winding is done insulate these cores. Due to silicon steel, the energizing current of the unit is very negligible and can take rated currents with out any burden on the units. The winding of the units are very close and the brush arm that rotates is mechanized in such a way that the brush tap always contacts more than one turn hence before leaving the first turn the brush tap contacts the second turn, hence it gives the uninterrupted output voltages. Capacities range from 2 a to 1800 a single-/three-phase.
