LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #1   Report Post  
Old January 15th 08, 12:05 PM posted to rec.radio.shortwave
external usenet poster
 
First recorded activity by RadioBanter: Dec 2007
Posts: 57
Default A rant against MOV's.

I have an intense dislike for MOV (Metal Oxide Varistors). 99% of all
the "transient protection" devices
available to the public are based on these devices.

While they work, they are prone to an almost certain dangerous
failure mode.

MOVs can only dissipate "X" amount of energy, after that amount of
energy has been "clamped",
MOV will start leaking current even when there is no over voltage
condition. This leads to thermal
"run away" and unless the MOV has a thermal cutout adjacent to it, can
result in fire. I several units
that are failing after surviving a close lightning strike. When
connected to the AC mains they all start
conducting several 199uA that rapidly ramps up to 30mA. I have never
allowed them to stay connected
to the AC mains because I really do not want to deal with a fire.
Another concern for me is that MOVs
that are failing often produce intense Radio Frequency Interference.

There is at least one company that produces a MOV with an internal
thermal cut out.

http://www.littelfuse.com/data/en/Articles/TMOVPCIMPaper.pdf.

This is not an idle threat. I have seen three house fires started by
MOVs and several electricians
I know have seen many such fires. Fortunately most fires are self
limiting and only the plastic case
chars and the fire putters out. But under the wrong conditions the
fire can spread to the structure.


Terry
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
your rant Christopher Cox Antenna 1 August 4th 07 01:28 PM
your rant Christopher Cox Shortwave 0 August 4th 07 12:42 PM
So Much For THAT Rant.... Steve Robeson K4CAP Policy 74 June 15th 04 05:40 AM
Theological Rant [email protected] Antenna 0 November 27th 03 05:58 PM
Rant Michael A. Terrell Homebrew 17 October 24th 03 04:42 AM


All times are GMT +1. The time now is 12:06 PM.

Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004-2025 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017