Relay will not open (but will close)

John Speth <johnspeth@yahoo.com> Wrote in message:
> I humbly thank all respondents for their help.  There is certainly a 
> wealth of hard-earned knowledge here considering how small the news 
> group has gotten.
> 
> In a nutshell, I think the contacts are welding shut due to arcing. 
> That's because we have little engineering information about the load 
> that's being switched.  We will characterize the power supply and take 
> steps to cor3ect deficiencies.
> 
> JJS
> 

Did you ever figure this out? I've got an index card in my head
 with the "answer" section blank
-- 
www.wescottdesign.com


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On 10/4/2016 6:24 PM, Tim Wescott wrote:
> John Speth <johnspeth@yahoo.com> Wrote in message:
>> I humbly thank all respondents for their help.  There is certainly a
>> wealth of hard-earned knowledge here considering how small the news
>> group has gotten.
>>
>> In a nutshell, I think the contacts are welding shut due to arcing.
>> That's because we have little engineering information about the load
>> that's being switched.  We will characterize the power supply and take
>> steps to cor3ect deficiencies.
>>
>> JJS
>>
>
> Did you ever figure this out? I've got an index card in my head
>  with the "answer" section blank
>

We have no root cause and we have no budget to get it.  A circuit 
workaround was implemented instead.

We wrecked three relays to various degrees.  Each was opened.  Slight 
contact debris was noted.  Since it's destructive to get a view of the 
contacts, we can't say if the debris is significant or not.

We think the load is capacitive enough to weld the contact when it 
closes.  Then it's stays welded until something jars it loose.  The load 
is a 500V power supply.  The power supply manufacturer was not helpful 
in providing any information other than what's in the data sheet.

JJS