Help with PSU (Temp control fan, load bank, & PWM circuit)

[Doctore]

Hi, I want to build this, but my electronic skills and englisch are not the best and I have few questions.
1 I can use this for ps's what have regulated voltage(0-25V, how many volts I can?)?
2 Anyone have complete schematic of dl1 for eagle in .sch ?
3 How many amps, If i have very good cooling system?
4 What other mosfect I can use?(because STP80NF12 are expensive in my country[PL])

Thanks.

 

[ronv]

Take a look at the end of this thread for the new version. If I remember right it is now 50 volts and 60 amps.

What FETs can you get locally with a high power rating?

1-Yes
2- No just LTSpice
3- Maybe 90 amps
4- It needs to be high power.

 

[Doctore]

Hi, thanks for fast reply.
I saw DL2, but DL2 is more expensiv.
Here are shops where i can buy parts:
Category with few mosfets https://www.lispol.com/index.php?a=product&b=list&str=mosfet&x=0&y=0
You can search mosfets here https://www.tme.eu/en/
and here https://allegro.pl/

 

[Doctore]

I find in tme.eu IRF2805PBF and IRF1407PBF, they will be ok?

EDIT: Some people on my polish electronic forum think this dl1 can work up to 100W, and themperature sensor will doesyn't work from this circuit:
https://obrazki.elektroda.pl/2524962100_1376343240.jpg
This is actual schematic of working DL1??

 

[ronv]

I find in tme.eu IRF2805PBF and IRF1407PBF, they will be ok?

Either one of those would work.

EDIT: Some people on my polish electronic forum think this dl1 can work up to 100W, and themperature sensor will doesyn't work from this circuit:
https://obrazki.elektroda.pl/2524962100_1376343240.jpg
This is actual schematic of working DL1??

The DL1 is running at 1200 watts. There are 10 FETs in total each one at about 120 watts.
The temperature sensor does not show the +12 connected.

 

[Doctore]

Jocanon have video on YT with this DL1 and this vid is named dummy load 1500+, so you tell DL1 is 1200W max?

 

[ronv]

It's difficult to say for sure how high it can go. The original design goal was 24 volts and 50 amps. A lot depends on the interface between the FETs and the copper cooling pipe and we could not calculate that exactly. I will probably do 2000 watts maximum but with no safety margin. We would need to recalculate with your FETs.
What are your requirements?

 

[Doctore]

Requirements are like actual DL1, 1500W and 50V are good.
What you suggest, solder mosfets to copper pipe(I would rather not), use silicone paste, or better paste with copper?
What must be themperature of cooling liquid?

 

[()blivion]

The cooling is 90% of the project. It is the reason for the projects prolonged success. The more cooling, the more watts it can take. Plain, simple, and straightforward.

That being said...

Using anything other than a soldered connection from the hot parts to the cooling pipe would be woefully inadequate. It simply will not transfer heat fast enough to keep the chips from dieing.




Edit: The cooling fluid can be room temperature, nothing special is required for that. The parts should never be allowed to exceed 100C during operation in my opinion.

 

[Doctore]

On what I have to be careful when soldering a mosfets to copper pipe?
This don't destroy them?
I have soldering skills but I never do this.
My boys thinks, max. temperature on mosfets must be >25C...

 

[ronv]

We should probably start a new thread for this..... I kind of worried about soldering the transistors to the pipe as well, but..... Somewhere in this thread there are some measurements of the case temperature, They are not exact, but very low (2 or 3C above the pipe as I recall). That is the unknown of the whole thing. If the boys are looking for something to do get them to check it. A single transistor would do. I for one would love to know a more accurate figure.

 

[jocanon]

...What must be themperature of cooling liquid?

I just want to back up ()blivion's response to the above. When I moved to Gilbert, Arizona where the temperature of the water is much warmer in the summer than it is in Buffalo, NY I was worried about the cooling properties at first. But from experience I can tell you that the mosfets hardly raise the water temperature at all. So as long as the water is at least around 20-30c you should be perfectly fine (30c water is not cold at all - but it still keeps the mosfets well below 50c).

Also, on a separate note, I was worried as well about destroying the mosfets when I soldered them to the copper pipe because at first I tried using my normal soldering station which was NOT cutting it. I had to get a full on torch and really heat that thing up since the whole copper pipe is like one big heat sink. Like ()blivion stated you have to solder the fets to the copper pipe to really get the heat transfer we need to cool the mosfets and you don't want a cold solder joint so you have to heat it up enough when soldering to get that bond. So what I did was first I pre-tinned both the mosfets and the copper pipe. Then I set up the copper pipe with clamps to hold it in place so that I could set the mosfets on it and gravity would hold them in place. Then I applied the torch to the bottom of the copper pipe (opposite side of the mosfets) until the heat was just enough to melt the solder and the mosfets fell down onto the pipe (the bulge from the solder held them up until the heat was enough to melt it). Then I also added a more solder, then I quickly moved the torch onto the next mosfet and took the heat off as soon as possible. I am not holding out as an expert on soldering, but this is what I did and the dummy load is still working today (except for the mosfets that I shorted out of course...but that's not related).

 

[()blivion]

Hi, thanks for your backup on the matter.

Yeah, when it comes to part temperatures, most electronic parts are made such that they will survive being soldered... for obvious reasons. And in this age of surface mount technology, most parts need to survive the entire full board soldering process. As far as I know, so long as the part is not powered and running when you get it that hot, they will perfectly well survive the process at least a few times over. It would be very difficult to use them in consumer electronics if they couldn't at least do this.

 

[Doctore]

Thanks guys.
Now I draw schematic on eagle.
I don't use water from tap, but I want to use 12pcs of 120mm PC fan, car radiator and of course good pump.
What temperature I will get with this cooling system?
Meybe 5°C lower than room temperature? Or lower?

 

[Doctore]

Ok, here is schematic:

It's correct?

 

[ronv]

Looks okay. Please add a 75 ohm between the output of each Op amp and the FETs. We had some oscillation that I think can be fixed with this resistor.

I would guess only a few C over room temperature.

 

[Doctore]

Like this?

 

[()blivion]

I agree with ronv, starting a new thread would be best. PM me the title and I may join in and help.