What feature improves a motor's ability to handle overload conditions, indicated by its Service Factor?

The correct choice, a multiplier value associated with horsepower, defines the Service Factor of a motor. The Service Factor indicates the motor's capacity to handle short-term overload conditions without sustaining damage. This factor provides a measure of how much more workload the motor can endure beyond its rated capacity (its nominal horsepower). For example, a motor with a Service Factor of 1.15 can theoretically handle 15% more than its rated horsepower for brief periods without overheating or failing, making it ideal for applications where occasional overloads might occur.

By contrast, the other options do not directly relate to the concept of Service Factor. While increased insulation class and enhanced bearing quality can improve overall motor reliability and performance, they do not specifically measure overload handling capacity. A special cooling system could also help in managing heat during overload situations, but it does not inherently enhance the motor’s ratings regarding overload capability as defined by the Service Factor. Thus, the multiplier associated with horsepower is the defining feature that enhances a motor’s performance in overload situations through the Service Factor.