What does Duty, Short-Time refer to?

Duty, Short-Time specifically describes a scenario where an electrical device operates at a constant load, but only for a predetermined short duration. This type of duty is often used in applications where the device may not be intended for continuous use and needs to perform its function effectively within a limited time frame without overheating or failing.

This definition aligns with various electrical equipment specifications, which may delineate short-time duty to indicate that after the specified duration of constant operation, the equipment might require a rest or cooling period. Understanding this classification is crucial when selecting equipment for specific applications or when ensuring that the equipment is used within safe operational limits laid out in the NEC.

In contrast, the other choices describe different loading scenarios. Operating at varying loads implies fluctuations in demand, which is not limited to a short duration. Operating at a constant load for a long period does not fit the "short-time" aspect, and alternating between load and rest indicates a different operational behavior known as intermittent duty, rather than a definitive short-time operation.