Variable Voltage Auto Transformer

Continously Variable Voltage Auto Transformer is the most effective device for stepless, breakless & continous control of AC voltage & therefore for various parameters, dependent on AC voltage.
These Variable Voltage Auto Transformers, consists of a single layer winding on a toroidal silicon-steel core. As the control knob is rotated, a carbon brush traverses the winding, tapping off a portion of the total voltage across the winding. The brush is in continous contact with the winding. The discrete voltage increments obtained as the knob is rotated are always less than the voltage between turns. Since the brush spans more than one turn, the change in voltage is practically continuous. As output voltage is continously variable, Variable Voltage Auto Transformers are rated in terms of current that can be drawn from the output.