CWells wrote: >>>I understand your concern in regards to the clearing time. However the PTCs are basically thermally driven and the so is the MOV failure. I believe one could balance the two with the proper sizing of the MOV and the series impedance of the PTC.
Wrong! A careful analysis will show that for any series combination of MOV and PTC thermistor, there is a voltage just above the MOV threshold where the MOV is still in a fairly high resistance mode while the (unheated) thermistor is a low resistance. Since current is essentially equal through the pair, heating will be largely confined to the MOV. True, the thermistor will shut the circuit down, but not until the MOV is damaged. >>>I plan to talk to the various vendors of MOVs and PTCs. If anyone has more experience in this area I would appreciate your input. Chris, I have extensive experience, including one patent (#5.379.022) assigned to a previous employer. I'd love to hook up with someone interested in a solution to this problem. Interested parties should contact me by email ([email protected]) or at: Heber Farnsworth 8029 137th Ave. SE Snohomish, WA 98290
