A fault in which coil causes a complete stoppage of voltage supply in the transformer secondary?

A fault in the open secondary coil causes a complete stoppage of voltage supply in the transformer secondary because an open coil interrupts the current flow. In a transformer, the secondary coil is where the output voltage is induced based on the magnetic field created by the primary coil. If the secondary coil is open, there is no closed path for current to flow, leading to zero voltage output despite the presence of voltage in the primary coil.

While other faults, like an open primary coil, might prevent the transformer from initiating operation, they do not directly result in the secondary coil's voltage supply being stopped after the transformer is powered up. Therefore, a fault affecting the secondary coil is crucial because it directly impacts the delivery of usable voltage to the load. Understanding this distinction is vital for troubleshooting and ensuring proper functionality of electrical systems involving transformers.