Author Topic: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?  (Read 11710 times)

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Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #25 on: September 19, 2017, 06:26:39 pm »
Please can you calm down Armadillo!

AC heat exchangers are likely different from CPU coolers as gas is pumped through them. I don't see any circulation in CPU coolers, just conduction.
 
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Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #26 on: September 19, 2017, 06:37:48 pm »
By the look of it, the plates look very thin,
All CPU coolers with heat pipes have thin plates, show at least one with thick plates to prove opposite.
Quote
And the region where the tube connects to the plates [compression flare] looks ..... ehm... not too promising.
All coolers with aluminium plates are made like this.
Quote
Then you wonder whether it is a genuine Heat Pipe technology, and the preferred orientation of the installation for the migration and return of the flow of the refrigerant inside the tube.
So, I would say you firstly need to calculate the required thermal resistance performance of the heat-sink before you buy one.
There are no non genuine heat pipes, it simply won't work at all. Such cooler won't be able to dissipate any significant heat.
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #27 on: September 19, 2017, 06:42:52 pm »
Hahahah, looks like the manifold disappeared.

 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #28 on: September 19, 2017, 06:46:55 pm »
LOL, you compare photos taken from different angle. It would be really surprising if aluminium plates became transparent.
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #29 on: September 19, 2017, 06:55:41 pm »
By the look of it, the plates look very thin,
All CPU coolers with heat pipes have thin plates, show at least one with thick plates to prove opposite.
Quote
And the region where the tube connects to the plates [compression flare] looks ..... ehm... not too promising.
All coolers with aluminium plates are made like this.
Quote
Then you wonder whether it is a genuine Heat Pipe technology, and the preferred orientation of the installation for the migration and return of the flow of the refrigerant inside the tube.
So, I would say you firstly need to calculate the required thermal resistance performance of the heat-sink before you buy one.
There are no non genuine heat pipes, it simply won't work at all. Such cooler won't be able to dissipate any significant heat.

The context was for the 200W DC load mosfet and NOT CPU, the fins look thin in terms of thin and fews for the load in question. It meant, If the fins is so widely spaced, it should be thicker for the loads.

@All coolers with aluminium plates are made like this. - hahahahahahah a piece of joke. So we should trust and buy without a doubt based on your assertion?

@There are no non genuine heat pipes, it simply won't work at all. Such cooler won't be able to dissipate any significant heat. - That may be why the mosfet blew in the first place. Hahahah LOL.  :-DD





 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #30 on: September 19, 2017, 06:57:19 pm »
LOL, you compare photos taken from different angle. It would be really surprising if aluminium plates became transparent.

LOL ok you had your point.
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #31 on: September 19, 2017, 07:13:48 pm »
Please can you calm down Armadillo!

AC heat exchangers are likely different from CPU coolers as gas is pumped through them. I don't see any circulation in CPU coolers, just conduction.




Then you wonder whether it is a genuine Heat Pipe technology, and the preferred orientation of the installation for the migration and return of the flow of the refrigerant inside the tube.

 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #32 on: September 19, 2017, 07:15:15 pm »
The context was for the 200W DC load mosfet and NOT CPU, the fins look thin in terms of thin and fews for the load in question. It meant, If the fins is so widely spaced, it should be thicker for the loads.
It would not help, thickness won't improve heat dissipation significantly, more dissipation area is needed for that. Fins are spaced normally. Closely spaced fins obstruct airflow and collect a lot of dust very fast. I did not say this heatsink is adequate for 200W heat dissipation, most likely it isn't.
Quote
Such cooler won't be able to dissipate any significant heat. - That may be why the mosfet blew in the first place.
MOSFET was stressed a lot beyond absolute max spec regardless if cooler was good or bad. And by significant heat I mean that if heat pipes were fake, such cooler won't be able to dissipate even 20W.
Quote
@All coolers with aluminium plates are made like this. - hahahahahahah a piece of joke. So we should trust and buy without a doubt based on your assertion?
Try soldering aluminium. Copper plates can be either compressed or soldered.
« Last Edit: September 19, 2017, 07:24:14 pm by wraper »
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #33 on: September 19, 2017, 07:40:31 pm »
The context was for the 200W DC load mosfet and NOT CPU, the fins look thin in terms of thin and fews for the load in question. It meant, If the fins is so widely spaced, it should be thicker for the loads.
It would not help, thickness won't improve heat dissipation significantly, more dissipation area is needed for that. Fins are spaced normally. Closely spaced fins obstruct airflow and collect a lot of dust very fast. I did not say this heatsink is adequate for 200W heat dissipation, most likely it isn't.
Quote
Such cooler won't be able to dissipate any significant heat. - That may be why the mosfet blew in the first place.
MOSFET was stressed a lot beyond absolute max spec regardless if cooler was good or bad. And by significant heat I mean that if heat pipes were fake, such cooler won't be able to dissipate even 20W.
Quote
@All coolers with aluminium plates are made like this. - hahahahahahah a piece of joke. So we should trust and buy without a doubt based on your assertion?
Try soldering aluminium. Copper plates can be either compressed or soldered.

Wraper to cut the story short - I was asking for the certified published thermal resistance value for this cooler. Do you  think is necessary to calculate it first before buying or using the cooler? Bear in mind, if you have not read it all, that the cooler is not the original cooler for the DC load.
« Last Edit: September 19, 2017, 07:42:06 pm by Armadillo »
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #34 on: September 19, 2017, 08:04:16 pm »

It would not help, thickness won't improve heat dissipation significantly, more dissipation area is needed for that. Fins are spaced normally. Closely spaced fins obstruct airflow and collect a lot of dust very fast.

Curious, Have you open up a proper DC load instrument before and appreciate the heatsink inside.?


MOSFET was stressed a lot beyond absolute max spec regardless if cooler was good or bad. And by significant heat I mean that if heat pipes were fake, such cooler won't be able to dissipate even 20W.

You calculated? can it be 20.1W .... hahahahah LOL.



 

Online Monkeh

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #35 on: September 19, 2017, 08:13:53 pm »
Wraper to cut the story short - I was asking for the certified published thermal resistance value for this cooler.

And just where do you think you'll find that for an aftermarket PC heatsink?
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #36 on: September 19, 2017, 09:17:49 pm »
Wraper to cut the story short - I was asking for the certified published thermal resistance value for this cooler.

And just where do you think you'll find that for an aftermarket PC heatsink?

You should answer the question if its important to know the value prior to the application in the first place and not a matter of excusing where to find it. That should beget the subject matter in question, don't you think so?
 

Online Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #37 on: September 19, 2017, 09:22:25 pm »
I see the OP hasn't bothered to come back - probably can't find anything of interest in the last page or so!  :palm:
Chris

"Victor Meldrew, the Crimson Avenger!"
 
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Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #38 on: September 19, 2017, 09:26:33 pm »
Hahahah, looks like the manifold disappeared.

This mounting somehow don't look right. Has the cooler been modified?
 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #39 on: September 19, 2017, 09:56:49 pm »

It would not help, thickness won't improve heat dissipation significantly, more dissipation area is needed for that. Fins are spaced normally. Closely spaced fins obstruct airflow and collect a lot of dust very fast.

Curious, Have you open up a proper DC load instrument before and appreciate the heatsink inside.?
Big aluminium heatsink(s) with a lot of mosfets mounted on it(them). No heatpipes because generally this is not needed as heat is evenly distribuited across the heatatsink by many mosfets. Fins are significantly thicker as distance heat needs to travel within fin is much longer. Do you even understand why thin plates are used in heatsink with heatpipes. Heat is delivered directly to the place where it is dissipated. If thicker fins will will be used, it will result in lower count of them in the same volume thus reducing performance. Can you explain by your wonderful theory why best CPU heatsinks like $90 Noctua NH D14 still use the same thin fins compressed onto the heatpipes? Also don't forget that CPU heatsinks are optimized for slow low noise fans, thus a lot of surface area is more important than thermal conductivity of the fins. Too low distance between fins besides dust accumulation cannot be used because fan at slow speeds don't produce high static pressure required to push air through.

« Last Edit: September 19, 2017, 10:04:37 pm by wraper »
 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #40 on: September 19, 2017, 10:24:15 pm »
BTW surprise, surprise. This is a heatsink which was cooling pentium 4 in old Dell PC, turned out I had one lying around. And fins are actually soldered to heatpipes. Also I stand corrected, this is the first time I see manufacturer bothered with trouble soldering aluminium to the heatpipes.

« Last Edit: September 19, 2017, 10:25:48 pm by wraper »
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #41 on: September 20, 2017, 03:23:02 am »
Here is the List of CPU thermal designed power from https://en.wikipedia.org/wiki/List_of_CPU_power_dissipation_figures

If the cooler was designed for it, would it be safe to assume those figures relatively speaking?

The next interesting things to know would be;

Do the heatpipe CPU coolers fail? How long will it last.?

How to test it?     http://www.dansdata.com/coolercomp.htm

 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #42 on: September 20, 2017, 06:53:24 am »
Big aluminium heatsink(s) with a lot of mosfets mounted on it(them). No heatpipes because generally this is not needed as heat is evenly distribuited across the heatatsink by many mosfets. Fins are significantly thicker as distance heat needs to travel within fin is much longer. Do you even understand why thin plates are used in heatsink with heatpipes. Heat is delivered directly to the place where it is dissipated. If thicker fins will will be used, it will result in lower count of them in the same volume thus reducing performance. Can you explain by your wonderful theory why best CPU heatsinks like $90 Noctua NH D14 still use the same thin fins compressed onto the heatpipes? Also don't forget that CPU heatsinks are optimized for slow low noise fans, thus a lot of surface area is more important than thermal conductivity of the fins. Too low distance between fins besides dust accumulation cannot be used because fan at slow speeds don't produce high static pressure required to push air through.



Elementary maths question?.

I think - The rate of heat input governs the thickness of the heat sink core and fins. Attached calculator for your learning.

The thicker the fins, the better the thermal heat resistance.

http://www.myheatsinks.com/calculate/thermal-resistance-plate-fin/

To understand the problems involved in higher load cpu cooler, read this; http://www.powerelectronics.com/content/heat-pipe-reliability-high-power-applications

For DC Load Bank use custom heatsink, period.

« Last Edit: September 20, 2017, 06:55:07 am by Armadillo »
 

Offline NANDBlog

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #43 on: September 20, 2017, 09:07:57 am »
Here is the List of CPU thermal designed power from https://en.wikipedia.org/wiki/List_of_CPU_power_dissipation_figures

If the cooler was designed for it, would it be safe to assume those figures relatively speaking?
These are the ghetto pentium 4 CPUs for poor people. Pentium 4 went up to some 130W, and they were easily dissipating above their TDP limit.
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #44 on: September 20, 2017, 09:25:30 am »
Here is the List of CPU thermal designed power from https://en.wikipedia.org/wiki/List_of_CPU_power_dissipation_figures

If the cooler was designed for it, would it be safe to assume those figures relatively speaking?
These are the ghetto pentium 4 CPUs for poor people. Pentium 4 went up to some 130W, and they were easily dissipating above their TDP limit.

Ghetto Cooler for Ghetto CPU, the subject in question.
« Last Edit: September 20, 2017, 09:51:14 am by Armadillo »
 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #45 on: September 20, 2017, 11:12:32 am »
Elementary maths question?.

I think - The rate of heat input governs the thickness of the heat sink core and fins. Attached calculator for your learning.

The thicker the fins, the better the thermal heat resistance.

http://www.myheatsinks.com/calculate/thermal-resistance-plate-fin/
Educate yourself. Fin thickness of this heatsink is 0.4mm, fin pitch 2 mm, distance heatpipe-heatsink center 25mm. I used this calculator, using this heatsink dimensions 105x88x55 mm (WxHxL). increasing fin thickness in this calculator from 0.4mm to 0.8mm increases pressure drop by around 3 times but reduces thermal resistance by 20% at the same airflow. The issue is, because of the pressure drop you won't be able to push the same airflow through it. All of this calculated for usual heatsink with 20mm base thickness, and not considering heatpipes which would make thermal resistance difference even less.
EDIT: if calculation is modified to use 25mm fin length to take heatpipes into account, when going from 0.4mm fin thickness to 0.8mm, thermal resistance decreases by only around 3-5% depending on airflow, yet again with drastic 3x pressure drop increase.
« Last Edit: September 20, 2017, 11:41:27 am by wraper »
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #46 on: September 20, 2017, 01:04:58 pm »

Educate yourself. Fin thickness of this heatsink is 0.4mm, fin pitch 2 mm, distance heatpipe-heatsink center 25mm. I used this calculator, using this heatsink dimensions 105x88x55 mm (WxHxL). increasing fin thickness in this calculator from 0.4mm to 0.8mm increases pressure drop by around 3 times but reduces thermal resistance by 20% at the same airflow. The issue is, because of the pressure drop you won't be able to push the same airflow through it. All of this calculated for usual heatsink with 20mm base thickness, and not considering heatpipes which would make thermal resistance difference even less.
EDIT: if calculation is modified to use 25mm fin length to take heatpipes into account, when going from 0.4mm fin thickness to 0.8mm, thermal resistance decreases by only around 3-5% depending on airflow, yet again with drastic 3x pressure drop increase.

Wraper says and wraper thinks but not a pinch of technical reference to support your warp logics... hahahahaha LOL.
At least those references provided by me gave you an insight on how the thicknesses of the fins are selected, not just always thin, thin and thin. And when the next time you open up that commercial DC load banks, you can appreciate more on how designers do it the right way. In future, if your logic is too wayward, and out of context, I may not consider to reply.

To sum it, the cooler used may not be sufficient to run the mosfet at 200 watts. It may be over-drived but further detailed tests and calculation may need to be done to support this. Hence custom designed heatsink or the manufacturer recommended heatsink will be more appropriate to be used for DC load banks, safely. This does not exclude other possible causes for the blown mosfet.    ;D
« Last Edit: September 20, 2017, 01:15:23 pm by Armadillo »
 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #47 on: September 20, 2017, 01:35:34 pm »
Wraper says and wraper thinks but not a pinch of technical reference to support your warp logics... hahahahaha LOL.
LOL, you posted a link to calculator, I made calculations. You call it warping logic  :palm: There is a compromise between surface area / fin count and fin thickness to achieve least thermal resistance in particular volume. If you want to increase fin thickness, you must decrease fin count  :palm:. Less fin count, less dissipating area. As with heat pipes distance heat need to travel through the fin is low, low fin thickness is optimal. All heatsink manufacturers must be stupid, Armadillo is smarter than all of them. Also in electronic loads there in no such size, noise, small heat source constrain, therefore cheaper heatsinks with larger size, thicker fins and larger gaps are used. Also such heatsinks are usually extruded, and you cannot extrude 0.4mm fins even if you want.
« Last Edit: September 20, 2017, 02:02:38 pm by wraper »
 

Offline iamdarkyoshi

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #48 on: September 20, 2017, 10:33:18 pm »
Can the heatsink sit flush to the mosfet.

And also the current sense wire, is it the original wire material? What material wire is used if not.

Just curious.

Thanks.

Its the original shunt. Anyway, I've been away and this topic kinda exploded. As suggested earlier, I'm going to parallel mosfets for better heat dissipation. I can fit four on this particular cooler.
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #49 on: September 21, 2017, 08:58:20 am »

Its the original shunt. Anyway, I've been away and this topic kinda exploded. As suggested earlier, I'm going to parallel mosfets for better heat dissipation. I can fit four on this particular cooler.

I see that you like to experiment. So how about progress to 400Watts 1KW Peak?



 


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