What is the likely consequence of operating a single-phase motor beyond its service factor?

Operating a single-phase motor beyond its service factor can indeed lead to overheating and eventual failure. The service factor is a multiplier that indicates how much overload the motor can safely handle without damage. When a motor is pushed past this limit, it typically experiences excessive thermal stress. As the temperature rises, insulation can break down, leading to short circuits or other failures. This overheating can also impact the lubrication of moving parts, causing additional friction and wear. The consequences of prolonged operation at this level are severe, often resulting in irreversible damage to the winding insulation and motor components, ultimately leading to motor failure.

The other options suggest positive outcomes, which do not occur when a motor operates beyond its specified limits. For instance, increased efficiency or lifespan is not aligned with operating conditions that stress the motor beyond its capabilities. Instead, a carefully managed operation within the service factor ensures reliability and longevity of the motor.