| Products > Test Equipment |
| New DL24EW and DL150W load testers from Atorch. |
| << < (4/5) > >> |
| SpottedDick:
--- Quote from: Filippo52 on February 03, 2023, 11:10:57 pm ---Thanks SpottedDick, but the problem is not the calibration but rather getting the maximum power dissipation. You can get this maximum only if the 4 mosfets work at the same temperatures otherwise the hottest ones will be the first to die followed by the others. By changing the heatsink with something much more robust, even keeping its fan at 150 W, you can get there. Currently I have arrived at 80 W with 40 °C with those ridiculous heatsinks that they put in and therefore even if it is not the temperature of the mosfet I think it is still a safety temperature. I have had it for a long time without any problems. By placing a 400 gr heat sink (8cmx8cmx 5cm heigth), a 50-55°C could be obtained with 130-150 W dissipated. I test these days and then I come here to report --- End quote --- I'm not sure that a 10% difference is going to let a MOSFET run away in thermal runaway. I'm also not convinced this wasn't intentional due to you and another user here getting the same value... Are you sure that isn't to cope with track resistance or something? 10% is that small in the grand scheme of things, that it does sound like track resistance. Remember you're talking to a seller here, and not the engineer. The engineer probably has 0 English and the seller hasn't a clue what you're talking about. The only way you'd know for sure would be to take off a MOSFET leg and do two opposite ones and see if it makes sense. Also, I have my original DL24 up to 350W with a water cooler and better MOSFET. Can you get me the model number they've used on the 150W version so I can check the COA curve and see where it should land, even with a 10% difference? |
| SpottedDick:
Just a note on the new unit, I can't really speculate on this until you send the model number, but the delta between temperatures matters a lot, something like this could make a massive difference, but obviously mounting is a problem. https://www.aliexpress.com/item/1005002971155868.html You would just need a €3 temperature sensor to control the Peltier device and turn them on/off at a certain temperature to get the delta up when you need it. |
| SpottedDick:
--- Quote from: SpottedDick on February 03, 2023, 11:21:16 pm ---# The only way you'd know for sure would be to take off a MOSFET leg and do two opposite ones and see if it makes sense. Also, I have my original DL24 up to 350W with a water cooler and better MOSFET. Can you get me the model number they've used on the 150W version so I can check the COA curve and see where it should land, even with a 10% difference? --- End quote --- I had a few beers last night before posting this! I meant test the actual current through each mosfet with a meter. I also meant SOA curve, not COA :D |
| Filippo52:
Spotted Dick, Measuring current doesn't seem difficult to me; the 0.22 and 0.25 ohm resistors are in series with the Mosfet so just measure the voltage across them to know the currents. It is exactly in this way that I have seen that they are unbalanced and that by reporting the equal value on all 4 mosfets the currents tend to be the same. For the mosfet model, both in the DL24 pcb and in the 4-mosfet DL24MP there are IRFP264 a greeting |
| SpottedDick:
Sorry, I'm bad at explaining things. I don't think you said which side are which, but I'll guess the 0.25 Ohms are on the left and 0.22 Ohms are on the right? If so it's probably to compensate for the additional track resistance to better balance the circuit. 0.03 ohms would make sense in that case. Measure the voltage from the green connector at the bottom left to the resistor on the MOSFET input side and see if that gives a better reading. On the IRFP264, that's great news. Once the heatsinks can keep up, that is certainly capable of 150W. Having a quick look at the data sheet and assuming my math is correct, running at 100°C, each of them can still do 50W, so 200W total. The junction temperature would be 137°C, so still a bit of headroom. Just a quick note before someone comes in, I know technically those MOSFETs are technically not rated for DC. |
| Navigation |
| Message Index |
| Next page |
| Previous page |