Thanks everyone!

Either test or re-design is required.


I appreciate the input.


John


________________________________
From: Doug Powell <doug...@gmail.com>
Sent: Tuesday, November 28, 2017 2:07 PM
To: John Allen
Cc: EMC-PSTC
Subject: Re: [PSES] Pickle

John,

UL 991 is a test method for qualifying solid-state circuits for safety 
function.  It is generally referenced by another standard and is not used as a 
primary certification standard as such.  Additionally, semiconductors are not 
certified individually to UL 991 as this is not a component standard.  It is 
very important that the circuits where the semiconductors are used be 
evaluated.  If you are familiar with the EMC immunity testing of IEC/CISPR 
standards, it is very much like this.  Radiated immunity, EFT, surge, ESD,  etc.

-Doug


Douglas E Powell
Laporte, Colorado USA
http://www.linkedin.com/in/dougp01
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On Tue, Nov 28, 2017 at 11:44 AM, John Allen 
<jral...@productsafetyinc.com<mailto:jral...@productsafetyinc.com>> wrote:

Hi,


We have a pickle of a situation and wondering if anyone knows a simple 
fix.........


We have a moving wall that complies with the maximum force limits of UL962.

An IC measures the voltage of a resistor and if appropriate, allows the correct 
current to be sent to a motor that moves the wall.

If too much current is allowed to the motor, the force created is greater than 
the limit.

We have a fuse, but it won't open before the force is created.


A UL991 investigation on the IC and Resistor circuit is necessary.  I agree 
with that.  That said -


  1.  I could not find any UL Recognized Component circuits that comply with UL 
991.  Is there such a category??  I searched UL's database for anything UL 991 
and came up with a few categories.  FSPC2 is a likely candidate, but the few 
Listings that are in there are heavy duty motor controllers or position sensing 
devices, etc.
  2.  If we redesign to not use the IC, won't we still be subjected to UL 991?  
If we use discrete components (resistors and capacitors vs ICs) does that get 
us out of UL 991?


Any insight would be appreciated.


Best Regards,


John


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