SRC Forum - Message Replies

Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

Original Message:

Posted by: Sue Hedrick
Date posted: Mon Mar 5 16:01:08 US/Eastern 2007
Subject: Resistor Calculation
Message:
With regard to resistor calculations, how can I determine theta EC. I had thought that it was calculated using (storage temp - max operating temp) / resistor power rating. This gives me huge numbers, greater than 600 deg C / W. What should I be doing?

Thanks, Sue

Previous reply

Reply:

Subject: Resistor Temperature/Temperature Rise
Reply Posted by: David Dylis
Organization: System Reliability Center
Date Posted: Mon Mar 5 17:51:37 US/Eastern 2007
Message:
In lieu of actual information, I would recommend using the PRISM default. Appendix G of the PRISM User Manual includes defaults for resistor temperature rise. These defaults vary based on the type of resistor being used. Defaults are as follows:

Resistor, Fixed, Carbon Composition: Temperature Rise = 20 Resistor, Fixed, Carbon Film: Temperature Rise = 30 Resistor, Fixed, General: Temperature Rise = 30 Resistor, Fixed, Metal Film: Temperature Rise = 30 Resistor, Fixed, Network: Temperature Rise = 30 Resistor, Fixed, Thermistor: Temperature Rise = 0 Resistor, Fixed, Wirewound: Temperature Rise = 20 Resistor, Variable: Temperature Rise = 25 Resistor, Variable, Film: Temperature Rise = 25 Resistor, Variable, Non-Wirewound: Temperature Rise = 20 Resistor, Variable, Trimmer, Composition: Temperature Rise = 20 Resistor, Variable, Wirewound: Temperature Rise = 0 Resistor, Varistor: Temperature Rise = 50

If you have additional questions, feel free to contact me.