>
>Careful, here.....MOV's shift characteristics with dosage, and
>may only be good for a few shots, depending on the charge it
>has to absorb, per shot.
>
? MOVs come in a wide range of repetitive peak-current abilities. The
little guys have thin wire leads and the biguns have strap leads.
Picking the right one for the job at hand is not difficult. When in
doubt, $pring for the next size up.
><snip>
>>a MOV across the contacts cures the problem better than a vacuum-
>>>relay since the reverse EMF still needs to be suppressed to prevent
>>>damage elsewhere.
>>
>>The problem is that because it's DC, even with no inductive load,
>
>? If wires are used to connect a (pretend) purely resistive load, the
>load always looks iinductive. And when the circuit opens, a reverse EMF
>at the opening contacts is guaranteed. Good engineering practice is to
>suppress reverse EMFs with a MOV or bi-lateral Si transient suppressor
>diode.
><snip>
>
>I did some work with MOV transient suppressors in a previous lifetime.
>If you zap them in opposite directions more or less equally, they can
>last a while. Zap them in one direction, like reverse EMF, and they
>will become increasingly less useful.
>
? When in doubt, read the fine print in the mfg specs.
>Jim N2EA
>
>PS: TWA's (retired) senior 747 check pilot at the time of the 'center
>fuel tank' explosion, still believes it was friendly fire that downed the
aircraft.
>
? As do many govamint conspiracy experts who have seen black helicopters
and Russky tanks in the corn fields of Kansas.
cheers, Jim
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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