Re: MOV & Surge Protection Questions
- From: "rayjking" <rayjking@xxxxxxxxxxxxx>
- Date: Sat, 13 Aug 2005 18:20:41 -0400
Robert,
The ac outlets in your house have millinery's worth of inductance back to
the pole transformer. When a high dv/dt rise in voltage occurs at the pole
transformer the large capacitance of the mov as well as its energy clamping
ability limit the voltage at the mov. every inch closer to the pole
transformer from the mov sees more voltage.
Ray
"Robert11" <rgsros@xxxxxxxxx> wrote in message
news:Stmdnc-8Fqg4gmjfRVn-ug@xxxxxxxxxxxxxx
> Hello:
>
> Have been thinking about this a bit, and realize I'm probably looking at
it
> the wrong way.
>
> The other night we had a moderate lighning storm come thru.
> Momentary loss of power; perhaps a few seconds.
>
> The only damage was to a newly installed furnace's circuit board which got
> fried. It obtains it power in the normal way, via a hard wired,
dedicated,
> 110 V
> branch back to a dedicated circuit breaker on the main panel.
>
> The surprising thing is that nothing else was damaged; even the PC worked
> fine afterwards.
>
> So, my questions are -
>
> Let's assume that there is only only one cheap extension cord outlet strip
> in the house that has MOV's for protection, and that the PC was plugged
into
> it.
>
> Let's also assume that it was connected to the L1 side of the 110V coming
> from the Service Box , as well as perhaps a dozen or so other circuit
> breakers and branch circuits.
> (the 220 V service coming in being split into two 110 V sections, L1 &
L2)
>
> It would seem to me that the MOV's in this strip, assuming they work(ed)
> really well would
> protect anything upstream just as well as anything plugged in downstream
> (like the PC's) as all they do is clamp the line to gnd. Upstream or
> downstream should make no difference.
> Is this correct ?
>
> By the same reasoning, I could argue that All the branches on L1 would be
> equally protected by this single MOV strip, as all of L1 would get
clamped.
> I guess there would by a few nsec difference in propagation times for the
> surge of the different branches, but it's hard to believe this would
effect
> anything.
>
> Are all branches coming off L1 equally protected by a single strip on just
> one of the branch circuits, do you think.
>
> Obviously the MOV strip it didn't protect the furnace circuit which was on
> L1, so I am probably wrong about this.
>
> Any thoughts on this would be most appreciated.
>
> Thanks,
> Bob
>
>
>
.
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