What type of transformer is connected to change supply voltage by ± 15% to deliver proper voltage to the load?

An autotransformer is designed to adjust voltage levels smoothly and efficiently, making it well-suited for applications where voltage needs to be fine-tuned, such as adjusting supply voltage by ± 15% for delivery to a load. The autotransformer operates on the principle of electromagnetic induction and utilizes a single winding that serves as both the primary and secondary winding, allowing for voltage adjustments without the need for multiple coils.

This design is highly efficient due to the shared winding, which minimizes energy losses. When the voltage is increased or decreased, the number of turns on the winding can be altered to achieve the desired voltage level. This flexibility is crucial in applications where precise voltage control is necessary to maintain the performance and safety of electrical equipment.

In contrast, isolation transformers primarily serve to isolate circuit components and enhance safety without altering voltage levels, while step-up and step-down transformers are designed specifically to increase or decrease voltage, respectively, but do not have the same variable output capability as the autotransformer.