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Author Topic: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?  (Read 3401 times)

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Offline iamdarkyoshi

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #50 on: September 22, 2017, 01:01:32 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?

-snip-

Probably not a bad idea, I've got enough computer heatsinks to easily dissipate like 5KW.
 

Offline iamdarkyoshi

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #51 on: September 23, 2017, 10:32:16 AM »
Well guys, I tried a set of two parallelled mosfets, and I got nowhere. The unit started to draw crazy currents at like 16V and higher. I switched it back to a single mosfet and it works fine. Any ideas? I'd really like to go over 100W on this thing.
 

Offline Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #52 on: September 23, 2017, 07:19:03 PM »
That sounds like parasitic oscillation. I'm not sure how long and tidy your wiring is but try a series 100R resistor right at the gate pin of each mosfet.
Chris

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Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #53 on: September 23, 2017, 09:26:14 PM »
Such a massive heatsink on a single package just looks 'wrong'.

probably can't find anything of interest in the last page or so!  :palm:

That sounds like parasitic oscillation. I'm not sure how long and tidy your wiring is but try a series 100R resistor right at the gate pin of each mosfet.

Getting interesting.     :popcorn:
 

Offline Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #54 on: September 23, 2017, 09:57:08 PM »
Can't say it's that interesting.  :-\   It would be nice if the OP can achieve his 200W goal though.
« Last Edit: September 23, 2017, 10:05:10 PM by Gyro »
Chris

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Offline Simon

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #55 on: September 24, 2017, 02:54:21 AM »
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.


And what is the speed of flow? would this make a difference to the type of construction like how many FPI?
The µCurrent has landed in Europe and now also selling Probe Master probes: http://www.simonselectronics.co.uk New stock now in.
 

Offline iamdarkyoshi

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #56 on: September 24, 2017, 11:04:26 AM »
That sounds like parasitic oscillation. I'm not sure how long and tidy your wiring is but try a series 100R resistor right at the gate pin of each mosfet.

I had the mosfets sitting right where the old one was, and some clever lead bending to get everything but the gate connected without extending them. The gate had probably about 1cm of extra wire.
 

Offline Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #57 on: September 24, 2017, 07:07:07 PM »
The extra gate capacitance of 2 mosfets causing the opamp(?) that's driving them to go unstable? The gate resistors would help there too btw.

It's really hard to say without some sort of schematic.
« Last Edit: September 24, 2017, 07:08:54 PM by Gyro »
Chris

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Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #58 on: September 24, 2017, 07:53:52 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.

This is a true high performance cooler with thermal heat resistance published. 
Caught your bullshits right there. Innocent members should know the truths.





 

Offline Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #59 on: September 24, 2017, 09:38:46 PM »
Curious that they describe a heatsink which is specified for 10-50CFM airflow as "Passive".

Presumable mainstream servers have big active fans.

My normal understanding of Passive is free-air.
Chris

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Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #60 on: September 24, 2017, 09:51:16 PM »
Curious that they describe a heatsink which is specified for 10-50CFM airflow as "Passive".

Presumable mainstream servers have big active fans.

My normal understanding of Passive is free-air.

Probably at this low and quite airflow is classified as passive.
As a comparison, the 4'X2' ceiling diffuser in a library would be about 500 cfm.
While the Noctua NHD14 is doing around 55cfm to 65cfm.

Edit: it would be interesting to know how Noctua performs in terms of Thermal heat Resistance.
« Last Edit: September 24, 2017, 10:10:38 PM by Armadillo »
 

Offline Simon

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #61 on: September 24, 2017, 09:55:06 PM »
Active versus passive us about method not quantity.
The µCurrent has landed in Europe and now also selling Probe Master probes: http://www.simonselectronics.co.uk New stock now in.
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #62 on: September 24, 2017, 10:05:18 PM »
Active versus passive us about method not quantity.

From the commercial world, apparently judging from the graph of quantified airflow, their definition is not the same as pure English....
 

Offline Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #63 on: September 24, 2017, 10:26:02 PM »
Haha yes, they commercially ommitted the high volume, high static pressure fan that needs to be ducted into it. We understand commercial English, it's called Marketing speak, nothing 'pure' about that!  ;D
Chris

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Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #64 on: September 24, 2017, 10:36:25 PM »
Haha yes, they commercially ommitted the high volume, high static pressure fan that needs to be ducted into it. We understand commercial English, it's called Marketing speak, nothing 'pure' about that!  ;D

Hahahaha,
Unless you can show case of that "BIG HIGH STATIC PRESSURE FAN" hook up, otherwise I tends to think more likely is just "BIG TALK".
I understand static pressure is proportional to velocity square V2, with that low airflow requirements, apple to apple comparison of the thermal resistance performance would be a better judge of the case really. Otherwise would we say, empty talk, the big version type.   :D

Edit:  Hahahahahahaha
« Last Edit: September 24, 2017, 10:38:43 PM by Armadillo »
 

Offline Gyro

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #65 on: September 24, 2017, 11:11:00 PM »
Haha no, I wouldn't presume to claim to be an expert in fluid dynamics. I could easily pick up that it wouldn't work in 'pure Engish' free-air passive any better than the same outer outline of solid Aluminium though (probably worse because the heatpipes wouldn't be able to condense and would stall) but much beyond that and normal enclosure airflow design and optimization...

Just by looking at the picture though (and roughly estimating it's dimensions from the base footprint as no dimensions are given) I can only guess that it would take a fair amount of static pressure to force anything like 50CFM though that block of so many, tightly spaced, fins.

Just my thoughts.  ;)
« Last Edit: September 24, 2017, 11:14:38 PM by Gyro »
Chris

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Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #66 on: October 01, 2017, 05:17:32 PM »
Just curious with OP updates?.    :popcorn:

Oh BTW, the dP [differential pressure] is shown on the right side of the graph.!
 

Offline iamdarkyoshi

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #67 on: October 19, 2017, 05:20:14 AM »
Just curious with OP updates?.    :popcorn:

Oh BTW, the dP [differential pressure] is shown on the right side of the graph.!

Ah I've been working on other projects but figured I'd check back here.

I'm going with a 140mm fan and two 1st gen mac pro heatsinks. If they can each cool a 95w CPU at fuckall airflow, they should cool a couple mosfets with a bigass fan :P
 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #68 on: October 20, 2017, 12:08:54 AM »
This is a true high performance cooler with thermal heat resistance published. 
Caught your bullshits right there. Innocent members should know the truths
Please elaborate how those pictures "caught me on bullshits" in any way?
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #69 on: October 20, 2017, 02:32:57 AM »
This is a true high performance cooler with thermal heat resistance published. 
Caught your bullshits right there. Innocent members should know the truths
Please elaborate how those pictures "caught me on bullshits" in any way?
 

Offline wraper

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #70 on: October 20, 2017, 02:50:11 AM »
OK, heatsink on the picture has heatpipes and very thin plates. Where is debunking ?
 

Online Monkeh

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #71 on: October 20, 2017, 02:55:33 AM »
OK, heatsink on the picture has heatpipes and very thin plates. Where is debunking ?

Perhaps he's seriously confused and was originally referring to my comment about finding thermal resistance numbers for aftermarket PC heatsinks. Which.. still isn't debunked as of yet, because that's not a PC heatsink sold to consumers, it's a server heatsink for ducted systems sold to OEMs..
 

Offline Armadillo

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #72 on: October 20, 2017, 03:16:00 AM »
OK, heatsink on the picture has heatpipes and very thin plates. Where is debunking ?

Perhaps he's seriously confused and was originally referring to my comment about finding thermal resistance numbers for aftermarket PC heatsinks. Which.. still isn't debunked as of yet, because that's not a PC heatsink sold to consumers, it's a server heatsink for ducted systems sold to OEMs..

I didn't even read your previous posts, hence what are you referring  to I don't know. ?????

Now, such ways of arguments are providing no added values to other members and is totally meaningless and a waste of time especially in a repair forum like this one, hence I will not entertain to further response regarding this subject.  Keep the peace.  ;Ds
 

Online Monkeh

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #73 on: October 20, 2017, 03:20:38 AM »
OK, heatsink on the picture has heatpipes and very thin plates. Where is debunking ?

Perhaps he's seriously confused and was originally referring to my comment about finding thermal resistance numbers for aftermarket PC heatsinks. Which.. still isn't debunked as of yet, because that's not a PC heatsink sold to consumers, it's a server heatsink for ducted systems sold to OEMs..

I didn't even read your previous posts, hence what are you referring  to I don't know. ?????

Didn't read it? You replied to it. Please take your alternate fact elsewhere.
 

Offline Simon

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Re: Blew a MOSFET dissipating 200W.... Fake mosfet or bad circuit?
« Reply #74 on: October 20, 2017, 03:44:20 AM »
Can we calm it down please. This thread is becoming pointless and a candidate for locking.
The µCurrent has landed in Europe and now also selling Probe Master probes: http://www.simonselectronics.co.uk New stock now in.
 
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