VARIABLE AUTOTRANSFORMER (VARYAK)

It is composed of a single-layer  winding wound on a toroidal iron core. Variac is often used  when  we wish to obtain  a variable AC voltage from a fixed-voltage  AC source. A movable carbon brush ,which can be set in any position between 0 and 330°, sliding on the winding and serves as a variable tap. Manuel or motorized control can be possible

ADVANTAGE

The secondary  winding  is actually  part of the  primary winding. In effect, a variac eliminates the need for a seperate secondary winding. As a result , autotransformers are always smaller,lighter, and cheaper  than standart transformers of equal power output.

Their iron and copper losses  are smaller and result of this  their efficient  beter than standart transformers.

Their leakege flux is  smaller  so  their regulation ratio  beter than standart transformers.