derated

Derated is an adjective used to describe equipment, components, or systems that are operated below their stated maximum capability. Derating is the deliberate reduction of a device’s allowable stress, current, voltage, power, or other rating in response to conditions such as temperature, aging, altitude, or duty cycle in order to improve reliability or safety.

In electronics and electrical engineering, derating is common for semiconductors, capacitors, transformers, and LEDs. It means allowing less current or power than the nominal rating as ambient temperature rises or as the device ages. For example, a device may be operated at a fraction of its nominal current when the ambient is high to keep junction or winding temperatures within safe limits; LEDs are often driven below their maximum rated current to control temperature rise.

In mechanical engineering and energy systems, derating accounts for altitude, vibration, wear, or lubrication state. Generators, turbines, and engines may produce lower output under adverse conditions while maintaining safety margins. Battery packs and energy storage systems also use derated discharge and charge specifications to preserve cycle life and safety. In software, thermal throttling can act as a form of derating by lowering processor frequency to reduce heat.

Manufacturers typically provide derating curves or factors, and standards bodies such as IEC or IEEE describe derating practices for different components. The goal of derating is to reduce failure probability and extend service life, at the cost of reduced performance and efficiency. Derated operation is thus a common and prudent design practice in engineering.