| Electronics > Projects, Designs, and Technical Stuff |
| My constant current load - 90W , 3A 30V |
| << < (12/19) > >> |
| blackdog:
Hi SeanB, Uhm, the diode is only for reverse protection... It is Not Mounted on a heatsink, just my way to mount it. The diode has only to blow the fuse. Regarts, Blackdog |
| Spikee:
Leech , you were almost correct . Whit a 1 ohm resistor of 100w i will be able to pull 10A max. My mosfet and heatsink can only handle around 120W max. At 12 volt i can utilize the resistors rating fully at 10 A. In my application i dont need to test high currents at low voltage so the 1 ohm 100W resistor is perfect. Thanks for the info , tomorrow i will recieve my parts and i can start testing the pc heatsink. Gr. Spikee |
| Spikee:
So i just mounted the 100W resistor and the mosfet on the heatsink. I mixed the artic silver stuff , put the two TO247 package opposite side of each other (to utilize the heatpipes fully) . Then i clamped them on the heatsink and applied ~10W on the 1ohm resistor so the curing would go faster. it was ambient temperature of 18 deg C here and now the heatsink is stable at 39 deg. C (no fan , upside down ) . You immediately see the advantages of heatpipes. the whole heatsink is at the same temperature and the fins got hot before the mounting plate. After a few mins the mounting plate and the fins get around the same temperature. Pic: Whole assembly: https://www.dropbox.com/s/3dse7kpoq3tft5k/2012-12-09%2023.05.08.jpg Mosfet and power resistor: https://www.dropbox.com/s/v9hmkshzxbjd6d1/2012-12-09%2023.06.18.jpg |
| Spikee:
So i just picked up my components at college ;D . The 1ohm 100w resistors are huge , do i need to put them on an external heatsink ? or can they handle the 100W just mounted on the metal case. Item number: WH100-1R0JI maybe i can fit them on the top of the processor side. pic: 50K ohm 10 turn pot 2x 1ohm 100W resistors 10x 0.1 ohm resistor 3W |
| T4P:
Check the given thermal specs (Tj-a and Tj-c) of the resistors as well as calculate roughly how much temperature rise you can tolerate on a heatsink (I would recommend not going over 85C if possible so) Think of the voltage drop (1V in your case so if you're pulling a amp it's 1W but surely it can handle it right? Actually such a huge resistor is somewhat overkill) If you're just pulling 3A, seriously it's only 9W I recommend using a fan or a better fan because those heatsinks IMO optimum-ly can't do more than 115W at 80C (50C rise i think?) at least |
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