[Boatanchors] MOV Choice for 120 VAC and 230 VAC

[Carl]

A problem with MOV's is that they have a finite life and can only handle xx 
# of spikes. Ive built them into several fused or breaker controlled outlet 
strips over the years and every one has eventually shorted.

Perhaps using ones meant for 240V in the strips and followed by 120V 
versions in the equipment after a fuse would give long term service??

I dont know as Ive since gone over to a couple of  1 kva CVT's found at 
fleamarkets for the various radio benches which each have their own on/off 
breaker controls. The CVT's have also resulted in quieter radios.

Carl
KM1H


>
>
> There is no 'right' answer. On the one hand, you don't want
> the voltage rating of the MOV to be too high so it won't
> provide real protection. OTOH, you don't want it too low,
> so a single spike will blow the MOV.
>
> My personal rule of thumb is to use 300V MOVs across the
> power line. By extension, I'd use 600V MOVs across 230V
> power lines. (MOV voltage rating above refers to peak
> voltage. Line voltage is in RMS).
>
> As to the energy rating, the higher the better. The rating,
> stated in Joules, refers to maximum energy the MOV may
> dissipate each time it 'fires'. In addition, MOVs do not live
> forever. Their life is a complex function of their past --
> number of times and amount of energy dissipated each time.
>
> BTW, paralling MOVs provides increased energy rating -- 
> in the ideal case, the sum of the energy ratings. In real life,
> rather less.
>
> - Ron
>
>
>
>
> ________________________________
> From: LEE BAHR <pulsarxp at embarqmail.com>
> To: boatanchors at mailman.qth.net
> Sent: Tue, March 16, 2010 2:10:01 AM
> Subject: Re: [Boatanchors] MOV Choice for 120 VAC and 230 VAC
>
> Is it wise to install a modern MOV across the primary of a boatanchor's
> power transformer input coil?  If so, which ones should I buy at Mouser 
> out
> of the zillion of them for sale there.  (I'd be interested in both those
> used on 120 volts AC well as 230 volts AC).
>
> I can't figure out which to buy.  Thanks for any input.  (I need to place 
> an
> order at Mouser for some other stuff and will ad MOVs at the same time).
>
> Lee, w0vt
>
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