Difference power dissipation and actual power dissipation

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Discussion Overview

The discussion centers around the distinction between "power dissipation" and "actual power dissipation" as it pertains to resistors, referencing the standard MIL-HDBK-217F for reliability. Participants seek clarification on these terms and their implications in practical scenarios.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asks for clarification on the difference between "power dissipation" and "actual power dissipation" for a resistor.
  • Another participant requests context, specifically if there are two different numbers for the same resistor in the same setup.
  • A participant cites the MIL-HDBK-217F, noting that "power dissipation" relates to the power factor while "actual power dissipation" relates to the power stress factor, but expresses confusion over the distinction.
  • One participant claims to have searched the handbook and could not find the specific terms, suggesting that the relevant section discusses electrical power stress ratios instead.
  • Another participant provides a different link to the handbook and points out where the terms are mentioned, but remains uncertain about their differences.
  • One participant proposes that "actual" may clarify the difference between the power dissipated by a component in a circuit and its nominal power rating, suggesting that "power dissipation" might be synonymous with "actual power dissipation" in some contexts.
  • A later reply expresses skepticism about learning from military specifications, suggesting that "actual" typically refers to a measured or confirmed value.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the distinction between "power dissipation" and "actual power dissipation," with multiple interpretations and uncertainties remaining in the discussion.

Contextual Notes

There are limitations in the discussion regarding the definitions of the terms and the specific context in which they are used in the handbook. Participants express varying interpretations of the terms without resolving the underlying ambiguities.

mepiace
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difference "power dissipation" and "actual power dissipation"

Hi,

Is it possible to explain me the difference between "power dissipation" and "actual power dissipation" for a resistor ? I really can't understand the difference...
 
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Do you have some context?
Do you have two different numbers for the same resistor in the same setup?
 
I am reading the standard MIL-HDBK-217F for the reliability of resistors and it talks about "power dissipation" and "actual power dissipation". It just says that "power dissipation" is connected to the power factor and the " Actual Power Dissipation" is connected to the power stress factor but i can't see or immagine any difference between "power dissipation" and "actual power dissipation".
 
mepiace, Welcome to Physics Forums!

I have downloaded MIL-HDBK-217F at http://www.sre.org/pubs/Mil-Hdbk-217F.pdf and searched the entire section number nine and cannot find those terms “power dissipation” and “actual power dissipation” anywhere. The only words similar are here:

“Section 9.0
The use of the resistor models requires the calculation of the electrical power stress ratio. Stress = operating power/rated power, or per Section 9.16 for variable resistors. ...The rated power for the stress ratio is equal to the full nominal rated power of the resistor.”

Will you please post the link or the exact quotation, in context, to assist members here respond to your question. Thank you.
 
difference "power dissipation" and "actual power dissipation"

Hi,

I have downloaded the standard MIL-HDBK-217F from a different site http://snebulos.mit.edu/projects/reference/MIL-STD/MIL-HDBK-217F-Notice2.pdf

Into the page 9-2 is mentioned the "power dissipation" in order to calculate the "power factor'. Into the page 9-3 is mentioned the 'Actual power dissipation" in order to calculate the "power stress factor". I don't know if there is any difference between "power dissipation" and "actual power dissipation".
 
In 9-3 I think the "actual" is just to make clear the difference between the power dissipation of the component in the circuit, and the nominal power rating of the component - e.g. a "10 watt" resistor that is actually dissipating 5 watts has S = 0.5.

In 9-2 "power dissipation" presumably means what it says, i.e. the same as "actual power dissipation" in 9-3.
But for a quick conservative estimate, assuming the components have been properly specified, you might use the component power rating in 9-2 instead. The failure rates for most resistors are likely to be low compared with other components in the system.
 
yes, it makes sense. Thank you very much for your answer!
 
OH dear god - please do not try to learn from Mil Specs... haha - in general the "actual" case tends to be a measured or confirmed value.
 

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