What is a significant risk of a three-phase motor experiencing single phasing?

A three-phase motor operating with single phasing is at significant risk of motor failure due to the sudden loss of power in one of the phases. In such a scenario, the motor is subjected to an unbalanced load, which can lead to overheating. The imbalance results in excessive currents in the remaining phases, causing the windings to heat up quickly and potentially leading to insulation failure. This overheating can also strain the motor's bearings and windings, compromising the motor's overall integrity and functionality.

In contrast, while single phasing may lead to increased power consumption and reduced efficiency, these outcomes do not pose an immediate threat to the physical structure of the motor like failure does. Similarly, increased load capacity does not apply as the motor does not maintain its optimal performance under such faulty conditions. Therefore, the most pressing concern with single phasing is the risk of motor failure, making it the correct choice.