What does a fast blow fuse protect against in transformer circuits?

A fast blow fuse is specifically designed to protect against short circuits in transformer circuits. When a short circuit occurs, there is a sudden and significant increase in current flow, which can potentially cause equipment damage or fire hazards. The fast blow fuse reacts quickly to this abrupt rise in current, effectively interrupting the electrical circuit before any significant damage can occur.

In contrast, the other options have different implications for fuse function. Surges in current, while potentially dangerous, are generally short-lived and may not trigger a fast blow fuse in the same immediate way as a short circuit would. Continuous overloads pose a different kind of risk, often involving prolonged high current levels that might not be addressed by a fast acting fuse, as these fuses are more responsive to rapid changes rather than sustained overloads. Lastly, "all potential failures" encompasses a wide range of issues, many of which a fast blow fuse may not protect against, emphasizing that its primary role is focused on immediate short-circuit conditions.

Thus, the role of a fast blow fuse is clear in its application to short circuits, ensuring effective and swift interruption of power in critical situations to protect both the transformer and the associated circuit components.