What is the result of overloading a transformer?

Overloading a transformer primarily leads to a reduction in its lifespan due to several factors. When a transformer is subjected to loads that exceed its rated capacity, it operates at higher temperatures than intended. This excessive heat can cause insulation materials to degrade faster, potentially leading to electrical failure or short circuits over time.

In addition to reduced lifespan, overloading can decrease the efficiency of the transformer. As the transformer heats up, more energy is lost as heat rather than being effectively transferred from the primary to the secondary side. This heat can also impact other components such as core materials, leading to further losses.

Furthermore, overloading a transformer can create conditions that might trigger protective devices, causing interruptions in service or necessitating shutdowns for maintenance and repair, aligning with the broader impacts of consistent overloading.

Thus, the correct answer reflects the reality that overloading a transformer has significant negative consequences, encompassing reduced lifespan and lower efficiency, rather than having no significant effect or improving efficiency.