Re: home surge protection
An MOV is a variable resistor that changes resistance with voltage. Another type of varistor's change resistance with temperature. In almost all surge suppressors they are rated at 130vac so their resistance changes to maintain a differential of no more that 130vac. The big problem with MOV's is that their switch time is about 10ms and a lighting strike is about 10ns much to fast for the MOV to even react.
The TVSS's clamp at + or - 15% nominal line voltage, that would be + or - 18vac for a 120volt unit and + or - 36vac for a 240vac unit. Switch time is 5ns
UPS's (uninterpretable power supplies) come in two types one the load runs off the line until power is lost and then the inverter converts the batteries output to ac the second type the load is always running off the inverter and batteries the line only furnishes power to keep the batteries charged. The first can cause problems due to the switch time and because you are running off the line is only as good as the filters that are also in the unit. The second has 0 switch time and does the best job of filtering the power but are more expensive.
There is absolutely nothing made that can guarantee protection from lightening. Lightening can jump across open switches and damage equipment that is not even on. Lightening is unique in that it can even come in on the ground line. The second UPS and possible the TVSS can only minimize chances.
Last edited by JLMCDANIEL; 10-18-2007 at 12:21 AM.
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