Derating Calculation

At 85°C, that 1W resistor can only handle ~0.54W. If you try to push 1W through it, it will fail prematurely.

P_max = 1.0 × [ (155 - 85) / (155 - 25) ] derating calculation

(the derating factor) is determined by the ratio of standard losses to total losses including harmonics: At 85°C, that 1W resistor can only handle ~0

Derating isn't just for power. Here are the critical parameters for common parts: Here are the critical parameters for common parts:

By performing these simple calculations, you move away from theoretical specifications and toward reliable, real-world performance. Whether you are sizing a cable tray or selecting a switching power supply, always ask yourself: "Have I accounted for the heat?"

: Closely packed cables or components transfer heat to one another, reducing individual capacity. 1. Transformer Derating (IEEE Standard C57.110)