"Fredxx" wrote in message
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On 22/12/2017 01:24, Rod Speed wrote:


wrote in message
...
On Thursday, 21 December 2017 17:34:30 UTC, Terry Casey wrote:
In article 11d4a51f-9e27-4915-a5bf-53dd39799856
@googlegroups.com, tabbypurr says...
On Thursday, 21 December 2017 11:18:44 UTC, The Other Mike wrote:
On Wed, 20 Dec 2017 15:11:25 -0800 (PST), tabbypurr wrote:

wattage ratings to avoid permanent damage from over-heating.

Some power resistors are only specified for claimed power
dissipation at minus 100C!

Care to point to a datasheet that shows that?

http://www.resistorsonline.com/wire-wound-resistor.html


But the table on that page is clearly headed "Rating at 70°C"!

There are 3 derating lines shown. How do you make sense of them?

For temps over 70C.

I have to admit I initially thought tabbypurr was a prat to not understand
the 3 lines, then I had a closer look and I can see his point.

Not on his silly claim that they only have their rated power at
-100C he doesnt. The table clearly shows they have that at 70C.

I might interpret the second line down on the graph to be potential
increased rating at lower temperatures based on the 70C rating, but the
3rd graph has me stumped apart from the graph ending at 250C. I then note
250C is the "Derate to Zero" spec. Why then do the first 2 indicate a zero
rating at 300C?

Yes, that graph is a mess, but thats a separate issue to his original silly
claim.