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John Fields wrote:
> >>>Nobody has yet answered my question: what are typical one-shot versus
> >>>lifetime joule ratings for MOVs?
> >>
> >>---
> >>I don't think there _is_ a one-shot rating after which the device
> >>has to be replaced.
> >
> >So any MOV can absorb a megajoule?
>
> ---
> I don't think so, and I don't think that's what can be inferred from
> what I said.
>
> John Popelish posted something interesting relating to your query.
> Did you read it?
>
One of the parameters of a MOV is the Maximum Continuous Operating
Voltage which is the voltage at which a MOV starts to conduct,
specifically the voltage (on average - lot of individual variation) at
which the current is 1ma. The MOV Joule rating is the single shot
energy absorption that shifts the MCOV by 10% (lower) which can be
considered a performance limit. At lower (but still relatively high)
energy hits, the MOV can progressively degrade.
With lower (but still relatively high) energy hits the MOV can have a
much longer life. See w_'s post:
http://www.littelfuse.com/data/en/Data_Sheets/CA.pdf
Fig 7-11 which gives the number of pulses that can be absorbed (1 to 1
million) at different surge current vs duration combinations - from
which surge energy can be calculated..
bud--
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