Re: hexfet mosfet get hot too fast

"Joerg" <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:JQr8g.3564$fb2.87@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
After that it's on to the DC test. Add a 2nd winding and send DC through
it, then look where the inductance begins to drop. I usually do that
differently, applying a ramp and looking where the slope begins the shark
fin. Typically wearing eye protection in case I make a mistake and the FET
turns into a spacecraft.

I do both simultaneously, on a probably indestructible rig.
http://webpages.charter.net/dawill/tmoranwms/Elec_Inductor.html
The IRFZ34 in use seems to bottom out at 80A peak or so, minus DUT
resistance.. I haven't run it short circuited yet. The flyback/power
resistor dissipates more power (when biased to 15V), on account of running
the transistor at a duty cycle in the 5 or 10% range.

Tested a whole bunch of stuff lately, seems those yellow and white-one-side
toroids used in 200-300W computer PSU's are roughly 200nH/T^2, and have eddy
current loss on the order of 0.2 ohm (expressed as one turn shorted with
said resistance).

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


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