Which transformer type is characterized by a donor winding shared with the input to allow automatic voltage adjustment?

Which transformer type is characterized by a donor winding shared with the input to allow automatic voltage adjustment?

• A. Step-up transformer
• B. Induction transformer
• C. Autotransformer
• D. Rectifier

Answer: (C)

Autotransformers use a single winding that serves as both the input and part of the output, with a donor (shared) portion connected to the input. By tapping this common winding, the secondary voltage is obtained by adding or subtracting turns from the primary, so the output adjusts automatically as the load or input changes. This design is compact and efficient because it uses fewer turns and less copper, making it cheaper for voltage adjustment tasks. The trade-off is lack of electrical isolation between input and output, since they share a winding. In contrast, a step-up transformer uses entirely separate windings to provide isolation, an induction transformer refers to the general transformer concept with separate windings, and a rectifier is a device that converts AC to DC rather than a transformer type. This is why the described feature points to an autotransformer.

Autotransformers use a single winding that serves as both the input and part of the output, with a donor (shared) portion connected to the input. By tapping this common winding, the secondary voltage is obtained by adding or subtracting turns from the primary, so the output adjusts automatically as the load or input changes. This design is compact and efficient because it uses fewer turns and less copper, making it cheaper for voltage adjustment tasks. The trade-off is lack of electrical isolation between input and output, since they share a winding. In contrast, a step-up transformer uses entirely separate windings to provide isolation, an induction transformer refers to the general transformer concept with separate windings, and a rectifier is a device that converts AC to DC rather than a transformer type. This is why the described feature points to an autotransformer.