Fred, While MOVs tend to be messy and TSBs can short both of these devices can fail in an open state as well. Or, the device shorts and a protection fuse may open. At which time the transient device is open, protection it afforded is gone and the equipment continues to operate. This is the undetected fault I am referring to. Any experiences in this situation?
Doug Douglas E Powell Independent Compliance Consultant http://www.linkedin.com/in/dougp01 http://www.linkedin.com/in/dougp01 -----Original Message----- From: FRED TOWNSEND <[email protected]> Date: Sun, 23 Sep 2012 18:11:40 To: <[email protected]>; <[email protected]> Subject: Re: MOV failure detection Doug I think your assumptions are correct. It's pretty much physical inspection. Specifically MOVs may split open and smoke may escape. Gas protectors usually fall open. Zeners (most semiconductors and carbon protectors) fail short and their no guarantee they won't burn a trace so UL sometimes requires fuses on such devices. Regards, Fred Townsend ________________________________ From: "[email protected]" <[email protected]> To: [email protected] Sent: Sun, September 23, 2012 8:31:19 AM Subject: MOV failure detection Aside from all the regulatory issues of leakage current and nasty failure modes of MOVs. What methods have been used to detect a failed transient suppression device in equipment? Or, is there some expectation the devices will survive a warranty period and that alone is good enough? Seems like any detection schemes would also have a series of regulatory issues and be a significant cost adder to the product. Doug Douglas E Powell Independent Compliance Consultant http://www.linkedin.com/in/dougp01 http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
