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Protection from overvoltage

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whiz115

Member
Hi

is it true that there is no way to get protection from a UPS in a bad whather conditions with lightnings?

though i don't have often lightnings in my area sometimes we get voltage spikes from the mains...so instead of spending money on a UPS (which i don't need...) or a multiple socket outlet with protections on it which usualy their prices are unreasonable high, i intent to build my own overvoltage protection using TVS and varistors.

i believe TVS are more effective than varistors but i got both of them.. the varistors are rated at 250V and the TVS at 128V and i'm going to use two TVS in series each one rated at 128V/1500W AC on 230V mains..


so i need some advices :)
 

BrownOut

Banned
Use both in parallel. The TVS will safely pass fast transients and the varistors will pass high current.
 

dknguyen

Well-Known Member
Most Helpful Member
Obviously, lightning is not the same as voltage spikesfrom the mains. Only gas discharge tubes will protect against lightening. You also have to check TVS diodes to make sure they are still working. Because they can fail open (like after supressing a bunch of spikes) and then they are no longer protecting but show no indication of it because normal operation is not affected.
 

Sydney

New Member
I live in the bush (country) in Australia. Here we suffer from supply fluctuations an severe lighning strikes, I find a good UPS where the device (TV or Comp) is supplied only from the battery is the best thing.

Think outside the square then square it.
 

whiz115

Member
thanks all of you for the replies!

Use both in parallel. The TVS will safely pass fast transients and the varistors will pass high current.
yes! that's exactly what i was thinking to do! two TVS (128VAC/1500W) in series one varistor and all in parallel


i also would like to know what does 16J and 50J means on the varistors, is it Joule? indicating max energy? and also i want to make sure that TVS can be connected both ways or if they behave as diodes...
 

kpatz

New Member
J = Joules, representing the maximum amount of energy the device can absorb.

TVSs come in unidirectional and bidirectional types. Use a bidirectional one for AC.
 
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