Hi Dean, thanks for finding that. I will be working on this project again at some point...some things happend in my personal life to really turn things upside down for me a few weeks ago, and then I got a great job offer from a CPA firm in Phoenix, AZ...to make a long story short, we are packing up and moving across country to good old AZ right now (yeah, I can get out of the snow!) So, as you can imagine, moving a family of 6 from Buffalo, NY to Phoenix, AZ is no small undertaking, it has been keeping me very very busy lately. Once I get settled in AZ and life gets pretty much back to normal I will be picking it up again. I still have at least 125 more power supplies to sell. If I can find a supplier of inventory to get more used DPS-600PBs in bulk (they seem to have dried up on eBay), or find a different power supply I can buy in bulk then I will likely be selling more than just the 125 I have left...so I definatley will be needing a dummy load to test them.
Seems like this thread has gone quiet so I'm not sure anyone is still working on this project but I've come across a FET that may be worth looking at. It doesn't have a logic level gate but everything else about it very good. If you want to drive them hard you might get by with as few as two, although I'd probably go with three or four to be safe.
https://www.fairchildsemi.com/ds/FD/FDL100N50F.pdf
A 2500 watt fet! unbelievable. Wait till Mr. RB sees this one. ...
2500W?? Bah! That's IF it is submerged in liquid nitrogen.
I'm beginning to think the cheaper manufacturers are starting to rate their parts in "whats?" instead of "watts" and it's going the way of the audio amplifier industry.
Jeremy is using water cooling at about 20C. I can't find where he did the measurements but as I recall he only had a case temperature rise of about 4C on the last FET in line so it is almost an infinite heat sink. He also measured the top of the TO220 and got a number very close to the calculated junction temperature so I almost belive it.
() The big difference in this FET is the thermal resistance junction to case for this guy is only 0.05C per watt whereas a TO3 like the 3055 has a junction to case of 1.5C/watt. So it is 30 times better getting the heat from the die to the case.
I'm not sure how they do that...
There's a heat sink calculator here: https://www.daycounter.com/Calculators/Heat-Sink-Temperature-Calculator.phtml where you can play around with the values and see what affect they have.
Here's an example (see attachment) where Thermal Resistance 1 is the stated case to sink resistance and Thermal Resistance 2 is the sink resistance.
View attachment 71443
JJ, If you still have 1 running would it be possible for you to measure the hottest spot on the plastic (opposite the metal tab)? I think we can get a good idea of the junction temperature from this and maybe refine Jeremy's or ()blivions data.
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