[TechAssist] Re: Question - internal 120V AC line varistors- surge suppressors
- From: Al Gutz <alg@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 10 Dec 2003 22:21:43 -0500
MOV works like your avalanche diode protect in a DC supply.
When it incoming AC voltage exceeds the rated operating voltage the MOV
shorts it to ground and opens the line fuse and in most cases dies in
the process. For 110V AC normally use 130V MOV with enough current
rating to open the fuse in unit.
Al G
"Phillip R. Hull" wrote:
>
> I was told there are different values of MOV depending on the current of the
> unit. For example a line MOV for a microwave oven that draws 15 amps,
> probably would not protect a TV set, because it would surge thru the unit
> before the MOV would short and blow the fuse.
> Phillip R Hull STET
> phil245@xxxxxxxxxxxxx
> FAX 517--569-3075
> Professional Technicians only
> ----- Original Message -----
> From: "Gary McCartney" <gary@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Tuesday, December 09, 2003 7:24 PM
> Subject: [TechAssist] Question - internal 120V AC line varistors- surge
> suppressors
>
> > In general, what is a good quality and rating of a varistor to use at
> > the 120V ac input of equipment where the varistor (surge suppressor) has
> > been blown up by a power surge?
> >
> >
> > Example, I have a Brother Intellifax 1270 fax machine that came in , hit
> > by a power surge. I found the varistor at the 120V AC power input (Z1 on
> > the power supply board) blowed up real good, along with the fuse which
> > was black as coal. These were the only faults as the fax machine works
> > now, however I don't know what varistor to use in place of the original.
> > Whatever the part was, it did a great job at protecting the power
> > supply. I will let the machine run awhile after repair in case the
> > mosfet switcher transistor was stressed in the action.
> >
> > What would be the recommended voltage and amperage surge rating to
> > replace the original with, perhaps purchased from Digikey or other
> > similar generic parts supplier?
> > --
> >
> > BTW, I titled the message the way I did because I thought I'd get more
> > responses than if I titled it, "brother fax machine....etc, etc.......)
> >
> >
> > Thanks for any help.
> >
> >
> > Gary McCartney
> >
> > McCartney Electronics
> > Guelph Ontario Canada
> > Est. 1984
> > email: gary (at) number63.ca
> >
> >
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