Deratingstabeller

Deratingstabeller, or derating tables, are reference charts used in electronics to adjust the rated limits of components for non-ideal operating conditions, primarily temperature. They provide guidance on how much power, current, or voltage a component can safely handle as ambient conditions change, with the aim of improving reliability and preventing overheating or premature failure.

Typically these tables cover a range of components such as resistors, capacitors, diodes, transistors, and power supplies. A table usually shows ambient temperature (or case temperature) on one axis and a derating value on the other, often expressed as a maximum allowable dissipation or current. Some tables use a curve rather than discrete steps. The resulting derated rating tells how much of the nominal capability is permissible under the specified conditions.

To use a derating table, identify the operating ambient temperature (or case temperature) and read off the corresponding derated rating. Apply the derating factor to the component’s nominal specification. Consider real-world factors such as airflow and mounting, which influence actual temperatures and may shift the applicable point on the derating curve.

Derating is commonly applied in resistor and semiconductor design, as well as in power supplies and other high-power assemblies. It may also factor in duty cycle for pulsed loads, altitude, and humidity in some tables. The purpose is to ensure long-term reliability by operating components well within their safe limits under expected environmental conditions.

Notes: derating tables vary by manufacturer and part family; they should be consulted in the specific datasheet. They are complemented by thermal design practices, including proper heatsinking, PCB layout, and adequate ventilation.