[AMPS] TL-922 Filament Transformer Protection

[Jon Ogden]

>>Did you take into account the fact that resistor dissipation goes down 
>>with increasing temperature?
>>
>€  This is clearly not the case.  Resistor dissipation is a function of 
>resistance and current squared.  

Bull, Rich.  Pure Bull!

I sell resistors for a living.  High power resistors at that.  RESISTOR DISSIPATION DROPS AS TEMPERATURE INCREASES!!!  That is a fact.  There is a temperature at which a resistors dissipation is ZERO.  Facts, pure and simple.  A resistor is able to dissipate power purely because of the fact that it can get rid of the heat that is built up.  As the temperature increases, it becomes more and more difficult to remove the heat.  Perhaps you've done the wonderful job of splitting hairs that you like to do.  I didn't make myself clear enough.  The maximum dissipation rating of a resistor decreases as temperature increases.  There is that clear enough?

Think about it, Rich.  Your argument doesn't make sense.  The dissipation that occurs in a resistor is the product or I^2*R, true.  But the maximum dissipation rating is a dependent upon a lot of things, one of them being temperature.  A typical dissipation curve is flat at 100% of rated dissipation to some temperature.  After that temp, the resistor then begins to linearly derate until it reaches 0% dissipation.

For example, I sell a 500 Watt flanged RF resistor (very non-inductive by the way).  It is capable of 100% dissipation out to 100 C.  At 150 C the dissipation is at 0 percent and at 125 C the dissipation rating is only 50%. That means that at 125 C this 500 Watt device can handle only 250 Watts of power.  At 150 C it's not even rated for a Watt!  And that's not an ambient temperature either.  That's the temperature on the outside of the device.

Rich, don't say things without thinking them through.  Face it, you are wrong on this one.

73,

Jon
KE9NA


--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!


Jon Ogden

jono@enteract.com
www.qsl.net/ke9na

"A life lived in fear is a life half lived."


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm