20A breaker, THHN, 3 conductors (no bundling derate), ambient 48°C.
The Derating Curve: This is the line that shows the "safe zone." As the temperature moves to the right, the curve typically stays flat for a while (the plateau) and then begins to slope downward. derating chart
In the realm of electronic and mechanical engineering, selecting a component based solely on its nominal "maximum" rating is a recipe for premature failure. A resistor might be rated for 10 watts, or a capacitor for 50 volts, but these figures usually apply only to ideal laboratory conditions. In the real world, factors such as ambient temperature, airflow, and proximity to other heat-generating components conspire to reduce a part's capacity. 20A breaker, THHN, 3 conductors (no bundling derate),
This is where the becomes an essential tool. It acts as a safety guide, telling engineers exactly how much "muscle" a component loses as the environment becomes harsher, ensuring that systems run efficiently and reliably over their expected lifespan. A resistor might be rated for 10 watts,
The engineer consults the derating chart and discovers that above 30°C, the PSU loses 2 Watts of capacity for every degree of temperature increase.