In my experience (and opinion), only slightly more than 15 watts is necessary
to raise plastic material to ignition temperature.
If a MOV is used as a SPD, then it should only operate (be conductive) in the
event of a transient over-voltage. If the transient event is the 1.2x50
waveform, the MOV should conduct for about 100-500 usecs. How long before the
MOV returns to quiescent resistance? I ask this question because the recovery
time will determine the heating power dissipation (from the mains voltage).
From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com]
Sent: Friday, November 17, 2017 10:05 AM
Subject: Re: [PSES] Regulatory requirements for MOVs placed line-to-ground on
AC mains ports?
I wonder if a 1A fuse would protect against MOV flameout just as well as a
100mA, if these MOV fail as an avalanche. (get hotter = more leakage) I've
seen some standards use 240VA (assume 240W) as a power limit for protection
against fire. However, I wonder if a MOV could burn nicely at say 0.5A without
further increase in current.
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