Go to Post Too many hours of robotics and too little sleep causes me to forget things.... - AdamHeard [more]
Home
Go Back   Chief Delphi > Technical > Electrical
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 17-07-2006, 01:47
sciguy125 sciguy125 is offline
Electrical Engineer
AKA: Phil Baltar
FRC #1351
Team Role: College Student
 
Join Date: Jan 2005
Rookie Year: 2004
Location: Sunnyvale, CA
Posts: 519
sciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond repute
Send a message via AIM to sciguy125 Send a message via MSN to sciguy125 Send a message via Yahoo to sciguy125
victor mosfets

Does anyone know what transistors are in the Victors? I was thinking of possible reasons that one of ours failed, but I need to look up some specs on the transistors.

I'd open one up, but I don't have access to any at the moment.
__________________

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GE/S/P a-- e y-- r-- s:++ d+ h! X+++
t++ C+ P+ L++ E W++ w M-- V? PS+ PE+
5- R-- tv+ b+ DI+++ D- G
------END GEEK CODE BLOCK------
  #2   Spotlight this post!  
Unread 17-07-2006, 08:03
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 8,904
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: victor mosfets

The FETs used are IRL3103 (International Rectifier) or an equivalent like FDB6035AL (Fairchild Semiconductor) for our competition victors.

http://www.irf.com/product-info/data...ta/irl3103.pdf

Digi-Key or Mouser have them.

This old thread discusses the victor's pretty in depth.
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle

Last edited by Mark McLeod : 17-07-2006 at 08:52. Reason: Added victor thread link
  #3   Spotlight this post!  
Unread 17-07-2006, 08:29
Gdeaver Gdeaver is offline
Registered User
FRC #1640
Team Role: Mentor
 
Join Date: Mar 2004
Rookie Year: 2001
Location: West Chester, Pa.
Posts: 1,370
Gdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond reputeGdeaver has a reputation beyond repute
Re: victor mosfets

Go to the IRC website. Lookup the data sheet on the IRL3103 and then go to the automotive applications and look up thru the hole automotive rated FETS. As you'll see there maybe some better choices for fets. The fets rated for automotive applications are designed to take more abuse that is found in cars. Would a fet swap in the victors be legal? Adding better heat sinking?
  #4   Spotlight this post!  
Unread 17-07-2006, 08:57
Joe Johnson's Avatar Unsung FIRST Hero
Joe Johnson Joe Johnson is offline
Engineer at Medrobotics
AKA: Dr. Joe
FRC #0088 (TJ2)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 1996
Location: Raynham, MA
Posts: 2,648
Joe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by Gdeaver
Would a fet swap in the victors be legal? Adding better heat sinking?
As to swapping fets, I can't see how the rules could be interpreted as allowing this.

As to adding heat sinks, I am not so sure. It may be legal, but why would you? I don't think the current ratings of the circuit breaker give much of a workout to the fets.

I say this, but I have never actually touched a fet after a match. Does anyone have any data how hot the fets run?

Joe J.
__________________
Joseph M. Johnson, Ph.D., P.E.
Mentor
Team #88, TJ2
  #5   Spotlight this post!  
Unread 17-07-2006, 09:08
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 3,674
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by Gdeaver
Would a fet swap in the victors be legal? Adding better heat sinking?
<R27> and <R59>, read together, appear to preclude using any controller other than a Victor 884 and any custom circuit component that directly alters the electric power pathway. A FET different than the ones originally provided in the Victor 884 would not comply.

I haven't found a rule against a custom cooling device; however, keep in mind that the tabs on a TO-220 package FET are common to the Drain terminal (middle pin), so some tabs are common to a motor output and others are common to the +12V power input. This means that heatsinks attached directly to FET tabs could become electrical fault hazards. I would not want to have to inspect Victors that had been modified by adding heatsinks directly to the FET tabs.

IMO the fan provided with each Victor is the most effective and safest way to cool it.
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
  #6   Spotlight this post!  
Unread 17-07-2006, 11:08
sciguy125 sciguy125 is offline
Electrical Engineer
AKA: Phil Baltar
FRC #1351
Team Role: College Student
 
Join Date: Jan 2005
Rookie Year: 2004
Location: Sunnyvale, CA
Posts: 519
sciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond repute
Send a message via AIM to sciguy125 Send a message via MSN to sciguy125 Send a message via Yahoo to sciguy125
Re: victor mosfets

Let's say that we backdrive a motor clockwise. Would the back EMF be the same polarity as that which we would need to apply to the motor leads to make the motor turn clockwise? Or does backdriving it reverse the polarity? I want to cite Lens' Law, but I'm not sure if it completely applies here.

On a side note, I noticed that the MOSFETs are rated for 64A. Where does the Victor's 40A limit come from? It's not the power limit because at 40A, it's only 19.2W and it's rated for 94W.
__________________

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GE/S/P a-- e y-- r-- s:++ d+ h! X+++
t++ C+ P+ L++ E W++ w M-- V? PS+ PE+
5- R-- tv+ b+ DI+++ D- G
------END GEEK CODE BLOCK------
  #7   Spotlight this post!  
Unread 17-07-2006, 11:25
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 8,904
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: victor mosfets

I pulled this note off a document somewhere, but don't ask me where.

"Typically the FET case's ability to dissipate heat limits this number(64A) to around 40 A per FET."
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle
  #8   Spotlight this post!  
Unread 17-07-2006, 12:05
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 3,674
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by sciguy125
Let's say that we backdrive a motor clockwise. Would the back EMF be the same polarity as that which we would need to apply to the motor leads to make the motor turn clockwise? Or does backdriving it reverse the polarity? I want to cite Lens' Law, but I'm not sure if it completely applies here.
Lenz's Law does apply here. A motor that develop's positive back-EMF when backdriven clockwise will also spin clockwise when positive voltage is applied at its terminals, assuming the mechanical load allows it to spin.

Quote:
Originally Posted by sciguy125
On a side note, I noticed that the MOSFETs are rated for 64A. Where does the Victor's 40A limit come from? It's not the power limit because at 40A, it's only 19.2W and it's rated for 94W.
Check out Fig. 9 on page 5 of the IRF3103 datasheet; it shows maximum drain current vs. case temperature. If your cooling system can hold the case temperature at 25 degrees Celsius then you can operate the FET at 64 Amperes drain current. At higher case temperatures, the maximum drain current decreases; e.g., at about 115 degrees Celsius case temperature the maximum drain current is 40 Amperes. Thermal analysis of FET installations can get complicated; however, in general the datasheet current rating is going to be higher than the current at which you can really operate the FET in a cost-effective system.
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
  #9   Spotlight this post!  
Unread 17-07-2006, 14:36
Joe Johnson's Avatar Unsung FIRST Hero
Joe Johnson Joe Johnson is offline
Engineer at Medrobotics
AKA: Dr. Joe
FRC #0088 (TJ2)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 1996
Location: Raynham, MA
Posts: 2,648
Joe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond repute
Re: victor mosfets

Don't forget that each leg of the h-bridge is really 3 fets. So, 40A per fet means 120A for the h-bridge total.

Lots of good things happen with parallel paths for the current.

Joe J
__________________
Joseph M. Johnson, Ph.D., P.E.
Mentor
Team #88, TJ2
  #10   Spotlight this post!  
Unread 17-07-2006, 15:29
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 3,674
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by Joe Johnson
Don't forget that each leg of the h-bridge is really 3 fets. So, 40A per fet means 120A for the h-bridge total.
As I said above, thermal analysis of FET installations can get complicated. To see how, let's use the Victor as an example:

As an extreme case, let's consider operating the FETs in free air with no convection. For this case, the data sheet provides a figure of 62 Kelvins (Celsius degrees) junction temperature rise (over ambient) for each Watt dissipated in the FET junction. A reasonable maximum for usable junction temperature might be 150 C, and ambient temperature on the FRC field might be 30 C, so the rise would be 120 Kelvins and the maximum dissipation would be 120/62 = 1.94 Watt. At 150 C junction temperature the FET's on-state resistance is Rds(on) = 0.02 Ohm [this was obtained by multiplying the nominal value 0.012 Ohm by 1.7, taken from Fig. 4 on the data sheet] so the maximum current in the FET is sqrt(1.94/0.02) = 9.7 Amperes. There are three FETs per leg, so the maximum leg current is about 29 Amperes. We can improve on this by running the cooling fan, which will reduce the thermal resistance from junction to ambient by a considerable factor, probably at least two. Using 31 Kelvins per Watt of dissipation and repeating the calculations above gives 3.87 Watts maximum dissipation for each FET and therefore 13.9 Amperes per FET and 41.7 Amperes per leg.

Of course this analysis predicts far less than the maximum 120 Amperes arrived at in the earlier posts; to get there, we would need to improve the thermal resistance from junction to ambient still further. A practical lower limit might be about three times the thermal resistance from junction to case (given as 1.6 degrees K/W by the data sheet) or 4.8 Kelvins per Watt. Using this figure, the maximum dissipation per FET is 25 Watts, the maximum FET current is 35 Amperes, and the maximum leg current is 105 Amperes. Based on the Victor's 40 Ampere rating, I'd guess that this level of FET cooling is probably beyond the capability of the Victor design. For reason's I gave earlier, it is probably not a good idea to try to retrofit the Victor with home-made heatsinks in an attempt to improve its thermal performance.
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
  #11   Spotlight this post!  
Unread 17-07-2006, 16:37
Joe Johnson's Avatar Unsung FIRST Hero
Joe Johnson Joe Johnson is offline
Engineer at Medrobotics
AKA: Dr. Joe
FRC #0088 (TJ2)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 1996
Location: Raynham, MA
Posts: 2,648
Joe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond reputeJoe Johnson has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by Richard
As I said above, thermal analysis of FET installations can get complicated. To see how, let's use the Victor as an example:

As an extreme case, let's consider operating the FETs in free air with no convection. For this case, the data sheet provides a figure of 62 Kelvins (Celsius degrees) junction temperature rise (over ambient) for each Watt dissipated in the FET junction. A reasonable maximum for usable junction temperature might be 150 C, and ambient temperature on the FRC field might be 30 C, so the rise would be 120 Kelvins and the maximum dissipation would be 120/62 = 1.94 Watt. At 150 C junction temperature the FET's on-state resistance is Rds(on) = 0.02 Ohm [this was obtained by multiplying the nominal value 0.012 Ohm by 1.7, taken from Fig. 4 on the data sheet] so the maximum current in the FET is sqrt(1.94/0.02) = 9.7 Amperes. There are three FETs per leg, so the maximum leg current is about 29 Amperes. We can improve on this by running the cooling fan, which will reduce the thermal resistance from junction to ambient by a considerable factor, probably at least two. Using 31 Kelvins per Watt of dissipation and repeating the calculations above gives 3.87 Watts maximum dissipation for each FET and therefore 13.9 Amperes per FET and 41.7 Amperes per leg.

Of course this analysis predicts far less than the maximum 120 Amperes arrived at in the earlier posts; to get there, we would need to improve the thermal resistance from junction to ambient still further. A practical lower limit might be about three times the thermal resistance from junction to case (given as 1.6 degrees K/W by the data sheet) or 4.8 Kelvins per Watt. Using this figure, the maximum dissipation per FET is 25 Watts, the maximum FET current is 35 Amperes, and the maximum leg current is 105 Amperes. Based on the Victor's 40 Ampere rating, I'd guess that this level of FET cooling is probably beyond the capability of the Victor design. For reason's I gave earlier, it is probably not a good idea to try to retrofit the Victor with home-made heatsinks in an attempt to improve its thermal performance.
I am not arguing that the heat analysis was simple, I am just reminding folks that there were 3 fets per leg.

As to the heat analysis, I would suppose that 31 Deg K per Watt is too high for forced air convection. This relatively small, clip on heatsink has rise of less than that based on natural (unforced) convection. A little bit of wind goes a long long way with respect to cooling.

Unless something happened that I am not aware of, Victors were not dropping left and right due to fet failure. Based on the years of service we have had with the Victor, I would guess that the 40A breaker is not allowing the fets to get anywhere near their temp limit. Based on that and assuming the math above is correct, I would estimate the effectiveness of the cooling to be higher than the 31 Deg K per Watt.

For Watt it's worth... ...;-)

Joe J.
__________________
Joseph M. Johnson, Ph.D., P.E.
Mentor
Team #88, TJ2

Last edited by Joe Johnson : 17-07-2006 at 20:34.
  #12   Spotlight this post!  
Unread 17-07-2006, 17:04
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 3,674
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by Joe Johnson
..., I would estimate the effectiveness of the cooling to be higher than the 31 Deg K per Watt.

For Watt it's worth... ...;-)

Joe J.
I agree, 31 K/W is a very conservative figure; IFI's 40A rating probably includes significant safety margin -- which I think is appropriate given their customer base!
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
  #13   Spotlight this post!  
Unread 18-07-2006, 23:28
sciguy125 sciguy125 is offline
Electrical Engineer
AKA: Phil Baltar
FRC #1351
Team Role: College Student
 
Join Date: Jan 2005
Rookie Year: 2004
Location: Sunnyvale, CA
Posts: 519
sciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond reputesciguy125 has a reputation beyond repute
Send a message via AIM to sciguy125 Send a message via MSN to sciguy125 Send a message via Yahoo to sciguy125
Re: victor mosfets

Alright, now just for a sanity check, MOSFETs short when they fail from too much current, right? I've seen several failed Victors and I'm reasonably sure that's what they do, but I can't remember.

Also, I have an internship this summer and I'm running tests on various devices and it seems that MOS shorts when it fails(unless of course you attack the gate). I'm working at the wafer level, but I don't see why things would change for a power transistor.
__________________

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GE/S/P a-- e y-- r-- s:++ d+ h! X+++
t++ C+ P+ L++ E W++ w M-- V? PS+ PE+
5- R-- tv+ b+ DI+++ D- G
------END GEEK CODE BLOCK------
  #14   Spotlight this post!  
Unread 19-07-2006, 09:15
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 3,674
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: victor mosfets

Quote:
Originally Posted by sciguy125
Alright, now just for a sanity check, MOSFETs short when they fail from too much current, right? I've seen several failed Victors and I'm reasonably sure that's what they do, but I can't remember.

Also, I have an internship this summer and I'm running tests on various devices and it seems that MOS shorts when it fails(unless of course you attack the gate). I'm working at the wafer level, but I don't see why things would change for a power transistor.
Short-circuit failure is typical on the wafer level. When large die are mounted and bonded to a single-device leadframe (e.g., TO-220) the weak link after such a failure is usually the source bonding filaments (for an n-channel device). Assuming sufficient fault current is available, these will burn open fairly quickly after the die has failed short. The result is that most discrete package power MOSFET failures are open-circuit by the time things cool off and you get to inspect the damage.
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
Closed Thread


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Victor on fire P1h3r1e3d13 Control System 6 21-02-2006 23:31
Inventor Victor punisher68 Inventor 5 14-03-2005 14:18
Victor qeustion sburro Electrical 13 23-04-2004 09:55
Victor 884's not behaving the same as Victor 883's programmer1 Programming 13 10-03-2004 21:51
Victor problem Andy Baker Electrical 15 24-06-2003 09:49


All times are GMT -5. The time now is 19:09.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi