For my pole transformer power cabinet I have used 2 MOVs in series across the 240 volt hot leads just after the 240 volt circuit breaker input to my power cabinet. Each of these MOVs is rated at 250 volt so the 2 in series should have a 500 volt breakdown voltage. I am going to change the topology so that each 120 volt leg of the 240 volt line has a 250 volt MOV connected between the hot wire and ground. These MOVs are heavy duty industrial units about the size of 2 decks of playing cards capable of withstanding 60,000 amp surges. I also have the other usual protection features in place such as line filters and a safety gap. I see the MOVs as a last resort if everything else fails.
The original configuration has been working for me for the last 6 months but lately I am questioning the use of MOVs at all. MOVs are made for infrequent surges and have a limited lifetime of surges they can absorb before failing, sometimes catastrophically. My SRSG has 4 flying electrodes yielding 240 breaks per second. To me this provides 240 opportunities per second to have an over-voltage event that can trigger the MOVs. This seems to me that the MOVs can be quickly worn out under this scenario.
Does anyone have an opinion on the use of MOVs on the 240 volt power line input? Does 250 volts sound too low for each 120 volt leg? I get different recommendations from different MOV application notes.
Steve
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxxxxxx
https://www.pupman.com/mailman/listinfo/tesla