What characteristic of a transformer limits current during a fault?

The characteristic of a transformer that limits current during a fault is its impedance. Impedance is the total opposition that a circuit presents to the flow of alternating current (AC), which includes both resistance and reactance. During a fault condition, such as a short circuit, the transformer’s impedance plays a crucial role in limiting the amount of fault current that can flow through the system.

When a fault occurs, the impedance of the transformer restricts the current due to the inherent resistance and inductive properties of the winding materials. This limited fault current helps protect the transformer and connected equipment from damage, allows protective devices such as circuit breakers to operate effectively, and maintains overall system stability.

In contrast, other options, such as voltage regulation, insulation rating, and transformer efficiency, do not primarily serve to limit current during fault conditions. Voltage regulation pertains to maintaining the output voltage within specified limits under varying load conditions. Insulation rating relates to the ability of the insulation materials to withstand voltage stresses without failing. Transformer efficiency concerns the ratio of output power to input power and primarily addresses energy losses rather than fault currents.