Technical Standards and Safety Authority (TSSA) G3 Practice Exam

What are transformers that share a winding or part of a winding called?

1. Step down transformers

2. Step up transformers

3. Auto transformers

4. Neutral transformers

The correct answer is: Auto transformers

Transformers that share a winding or part of a winding are referred to as auto transformers. An auto transformer has a single winding that acts as both the primary and secondary, allowing for the transformation of voltage levels while using a portion of the same winding for both purposes. This design results in a more compact transformer that is typically more efficient than traditional two-winding transformers because it reduces the amount of copper and material needed. In the case of auto transformers, the shared winding provides the necessary electromagnetic coupling between the input (primary) side and the output (secondary) side, facilitating voltage adjustment. For instance, they can either step up or step down the voltage effectively by tapping into different points along the winding. Step-up transformers and step-down transformers refer specifically to types of transformers designed for increasing or decreasing voltage levels, but they do not share a winding in the same way that auto transformers do. Neutral transformers, on the other hand, are used in specific applications related to grounding and do not describe the aspect of shared windings linked to the transformer mechanisms themselves. Auto transformers are therefore unique in their construction and operation, making them the correct answer to the question regarding transformers that share a winding.