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Unread 19-03-2011, 16:57
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Mike Betts Mike Betts is offline
Electrical Engineer
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Team Role: Engineer
 
Join Date: Dec 2001
Rookie Year: 1995
Location: Homosassa, FL
Posts: 1,442
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Re: pic: Well there's your problem...

Jared,

Actually, what you see could very well be the result of the failure and not the root cause...

When a power semiconductor fails, it almost always causes a resultant short circuit. This has to do with the inner structure of the device. The actual cause of the failure could be a voltage spike, over-current, loss of cooling (over-temperature), et cetera.

As an example: An over-current condition can be the result of a logic failure upstream of the device causing a "shoot-through" condition (the upper and lower halves of a power pole turn on simultaneously shorting the 12V to ground). This logic failure could be caused by a piece of aluminum dust shorting out two pins on an IC chip elsewhere on the board.

So when you see power devices failed like this, think of it as an indicator that something else failed...

Of course, the failure could indicate a manufacturing defect or a design deficiency as well...

I hope this makes things a little more cloudy for you... Welcome my world...

Regards,

Mike
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Mike Betts

Alumnus, Team 3518, Panthrobots, 2011
Alumnus, Team 177, Bobcat Robotics, 1995 - 2010
LRI, Connecticut Regional, 2007-2010
LRI, WPI Regional, 2009 - 2010
RI, South Florida Regional, 2012 - 2013

As easy as 355/113...
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