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From: Hamid Wasti <hwasti@lm50.com>
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Subject: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully thinking through
 failures
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Correcting a typo in my previous e-mail. The changes in the new 
paragraph are highlighted.

Hamid Wasti wrote:
> Lets say you have a system where the "A Buss" and "B Buss" feed an 
> essential buss and the diode on the A Buss side has failed with high 
> resistance. If you do a system check at every startup where you 
> sequentially shut down both busses and make sure that the essential 
> buss can run from the remaining one, you are likely to find that the 
> essential buss works. The failed diode will be able to operate the 
> load for a little bit while it over-heats. During normal operation, 
> the diode on the A Buss will take all the load. But if you have a 
> failure of the A Buss and all the current starts going through this 
> high resistance diode, it is quickly going to fail and as Murphy's Law 
> states, there is 100% likelihood that this will be one of the 30% of 
> times where it fails open.
Lets say you have a system where the "A Buss" and "B Buss" feed an 
essential buss and the diode on the _*B Buss*_ side has failed with high 
resistance. If you do a system check at every startup where you 
sequentially shut down both busses and make sure that the essential buss 
can run from the remaining one, you are likely to find that the 
essential buss works. The failed diode will be able to operate the load 
for a little bit while it over-heats. During normal operation, the 
_*good*_ diode on the A Buss will take all the load. But if you have a 
failure of the A Buss and all the current starts going through this high 
resistance diode _*from the B Buss*_, it is quickly going to fail and as 
Murphy's Law states, there is 100% likelihood that this will be one of 
the 30% of times where it fails open.

Regards,

Hamid