At 05:50 PM 8/6/2019, you wrote:
MOVs have tendancy to blow up. i wont use them. Russ wb3fau
I build in MOVs wherever I can into older electronic equipment that
does not have them, or home brew stuff, and never had any problems.
Without knowing more details about your particular situation, if your
MOVs keep blowing up it is because they are trying to do their job
protecting equipment absorbing overvoltage surges but you have not
provided a means of overload protection for them (fuse, circuit
breaker, etc) which in the case of big voltage spike or surge might
cause the MOV to go short circuit while trying to take the hit and if
there is no fuse it will blow itself apart trying to absorb the
additional inbound energy of the surge/spike.
In my experience 130V MOVs and the diameter of about a nickel to a
quarter are more than adequate to operate inside equipment that will
run off 120-125V AC mains, and will chug away quietly protecting
transformer primary windings, etc. Perhaps you have selected the
wrong MOV voltage specification for your particular area AC mains
voltage, or maybe you need a higher energy capacity device able to
withstand more surges.
BTW MOVs don't have an unlimited lifetime and will wear out over time
they clamp and dissipate incoming surges and spikes, but each event
will cause some cumulative wear and eventually will reach a point
where the MOV might either go completely short circuit and blow the
hopefully existing main AC input fuse and isolate the protected
equipment from any damage. Or go open circuit and blow up if no fuse
protection is in place between the mains input and the MOV. So never
install them without adequate overload protection in place, otherwise
you might get taken out with a nice bang during a heavy voltage surge
overload event, but your equipment might still get damaged all the same.
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