A voltage stabilizer is an electrical appliance that delivers a constant voltage to a load at its output terminals, regardless of the changes in the input or incoming supply voltage. It protects equipment or machinery against over voltage, under voltage, and other voltage surges.  They are often used for costly and precious electrical equipment to protect them from harmful high/low voltage fluctuations. This is ideal for industrial and automated machinery.

Electrical equipment is designed for a wide range of input voltage. Depending on the sensitivity, the working range of equipment is limited to a specific value, for instance, some equipment may tolerate ± 10 percent of the rated voltage, while others may tolerate only ± 5 percent or less.

Enerdoor specializes in single and three phase voltage stabilizers that regulate voltage through a series of transformers.  A static control circuit drives the variable autotransformer that supplies the required voltage to a series transformer to bring the main to the rated value.