Hello,
(When talking about power, I will be referring to continuous load. Pulsed is another discussion, and isn't relevant to my problem.)
When I learned electronics it was that an XXX watt resistor could be loaded up to XXX watts. So, when I purchased some aluminum encased 100W resistors, I thought I could load them at 100W.
Today I placed two of them in parallel under a 200W load (100W per resistor -- 10v @ 10a). I was trying to measure the temperature another part of the circuit and so I had a laser thermometer in hand. I smelt a funny scent, so I checked their temperature. They heated up, and not just by a little. They hit 274C! Now each of them had a dedicated 12v 120mm fan pointing at them (rated at ~2300rpm, 44CFM). The room temperature couldn't have been higher than 30C (the thermostat on the AC said 27.8C). Obviously, I disconnected the power when I saw how hot they were.
Here's the resistor type I have: https://www.aliexpress.com/item/1005003040560587.html
Are 100W resistors really 100W?
Is there some kind of derating curve that my book on electronics didn't go into?
How hot should these aluminum encased resistors get?
Thanks!
(When talking about power, I will be referring to continuous load. Pulsed is another discussion, and isn't relevant to my problem.)
When I learned electronics it was that an XXX watt resistor could be loaded up to XXX watts. So, when I purchased some aluminum encased 100W resistors, I thought I could load them at 100W.
Today I placed two of them in parallel under a 200W load (100W per resistor -- 10v @ 10a). I was trying to measure the temperature another part of the circuit and so I had a laser thermometer in hand. I smelt a funny scent, so I checked their temperature. They heated up, and not just by a little. They hit 274C! Now each of them had a dedicated 12v 120mm fan pointing at them (rated at ~2300rpm, 44CFM). The room temperature couldn't have been higher than 30C (the thermostat on the AC said 27.8C). Obviously, I disconnected the power when I saw how hot they were.
Here's the resistor type I have: https://www.aliexpress.com/item/1005003040560587.html
Are 100W resistors really 100W?
Is there some kind of derating curve that my book on electronics didn't go into?
How hot should these aluminum encased resistors get?
Thanks!