That's right, if any MOV fails, it fails by leaking more and more and more and more and then somebody is going to say aauauauauaua........................:<(((
No kidding, you may use MOV's for surge suppressing between phases, but not connect it to ground for the reasons above. You may use MOV's for surge suppressing between phases, but not connect it to ground for every MOV that fails slowly start leaking and leaking and finishes as a short circuit. In the philosophy of LVD a double protection of a Class 1 apparatus consists of: - Isolation + earth bounding ( 2 levels of protection agains electric shock) That would invalid one of the protection layers, as the MOV is no isolation , and not equivalent to an isolation layer. BTW Double Isolated apparatus Class II have two protection layers too, Isolation + extra isolation. ( 2 levels of protection agains electric shock) In both classes a single failure would not lead to catastrophy. I suppose the guys at UL started to learn something from their TUV german collegues ?! Regards Gert Gremmen , Ing. == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Member of NEC/IEC voting committee for EMC. Our Web presence: http://www.cetest.nl List of current harmonized standards http://www.cetest.nl/emc-harm.htm 15 great tips for the EMC-designer http://www.cetest.nl/features01.htm -----Oorspronkelijk bericht----- Van: [email protected] <[email protected]> Aan: [email protected] <[email protected]> Datum: dinsdag 21 april 1998 16:46 Onderwerp: Re: Use of MOV's ??? > > I recently received an e-mail from a colleague on the east coast > stating that UL has joined TUV Rheinland in NOT accepting the use > of MOV's in primary circuitry. > > The reasoning behind this is due to the unpredictable dielectric > break down of these components which can increase leakage current > beyond acceptable levels. > > > Has anyone heard any truth to these statements ? > If so, what other methods are being used to solve problems > without these devices? > > Your comments are appreciated, > > Jeff Collins EMC/Product Safety Engineer > Perkin-Elmer Applied Biosystems > [email protected] > > >
