What's inside overvoltage protectors?

[Behemot]

I am thinking about making custom OVP. The question is, what's inside the OVP (I mean the pricier extension cord with switch) you can usually buy?

I did not look into any yet, but I'd expect a few varistors in parallel, probably fuse an maybe some caps (also good for high frequency noise filtration).

I was thinking about giving it also few coils in parallel in adition to some X and Y caps. Also would a transil in series with the fuse be good idea? It could save some miliseconds before the fuse blows up. Of course this is just for really high overvoltage (like when lightning hits distribution network).

[Th3_uN1Qu3]

Re: What's inside overvoltage protectors?

They contain a few MOVs (or transils however you want to call them), some X caps, and not much else. The MOVs are placed in parallel with the outputs not in series, their job is to eat any high spikes. Since overvoltage spikes are typically short in duration, they don't get hot. And if they do, they're designed to fail short so they blow the fuse.

[Behemot]

Re: What's inside overvoltage protectors?

OK, I see now…

Thanks, I'll try it in next months.

Wow, I see they now have superfast (FF) fuses in local shop…I'll take the 20A one since the extension cord I use is made for 16 A.

[goodpsusearch]

Re: What's inside overvoltage protectors?

http://www.hardwaresecrets.com/artic...uppressors/483

This may help

[delaware74b]

Re: What's inside overvoltage protectors?

A good power strip, etc usually has 3 MOVs or banks of 3 MOVs. Simply, Line-to-Neutral, Line-to-Ground, and Neutral-to-Ground.
I've installed panel surge protectors which help protect all circuits in the house. Those models have 5-way protection: Line1-to-Neutral, Line2-to-Neutral, Line1-to-Ground, Line2-to-Ground, and Neutral-to-Ground.
On a side-note, I've seen the damage from a bad neutral connection compounded by a bad ground. I found voltages over 170 volt to ground. Obviously, all the electronics and appliances in the house were toast.

[Toasty]

Re: What's inside overvoltage protectors?

Also note that these "wear out" over time. Their effectiveness (ability to "consume" spikes) falls off depending on their age and the number of spikes and volume of joules they have sustained.


Toast

[Behemot]

Re: What's inside overvoltage protectors?

Yeah I know about that…for that reason I'll probably also change all MOV's in protectors I already have at home when I'll be doing this one.

[delaware74b]

Re: What's inside overvoltage protectors?

Also note that these "wear out" over time. Their effectiveness (ability to "consume" spikes) falls off depending on their age and the number of spikes and volume of joules they have sustained.


Toast

True, they do wear out from absorbing the surges. Well-made surge protectors do have fuses and status indicators to show when they have expired.

[Behemot]

Re: What's inside overvoltage protectors?

Well, IIRC, I have one APC SurgeArrest and two Belkins, both has some diodes. APC says the diodes won't be on when it's damaged, does this also mean the MOV's are still good, or it's jsut for serious damage (when half of it is burned).

Anyway, as I see, at least the APC works only for surges greater than 0,9 kV so it probably is not so much weared out. The electrical grid is sometimes hit by lightning, but I'd say most of the times it hits the huge transforming station few kilometeres away where they should handle it. So we see lights blink during storms few times a year, but nothing terrible. Most of the time, it probably just does nothing.

[Wizard]

Re: What's inside overvoltage protectors?

Other types is spark gap used in various applications. One was to limit voltage on the start up of HID lamp for rear projection TVs and in other uses replacement in place of MOVs. Either a cylindrical look or a neon-like bulb design. Much more reliable than MOV.

Cheers, Wizard

[Behemot]

Re: What's inside overvoltage protectors?

Isn't it only for high voltage? If there is a gap, I can image only that can go across it…

[Behemot]

Re: What's inside overvoltage protectors?

I was thinking about this one http://www.ges.cz/-siov-s20k175-ges05313492.html

It has pretty low voltage when it starts absorbing so it will filter out lower spikes protecting even the input capacitor. The question is how quickly it will wear out than? I have no doubts about "quality" of the grid.

[Slakky]

Re: What's inside overvoltage protectors?

Isn't it only for high voltage? If there is a gap, I can image only that can go across it…

Yeah, spark gap devices have a much longer response time. They're only useful in conjunction with MOVs or transorbs for sensitive equipment.

[severach]

Re: What's inside overvoltage protectors?

I was thinking about giving it also few coils in parallel in adition to some X and Y caps. Also would a transil in series with the fuse be good idea? It could save some miliseconds before the fuse blows up. Of course this is just for really high overvoltage (like when lightning hits distribution network).

Fuses and breakers cannot protect connected equipment from lightning. To blow the fuse the entire circuit must be carrying enough current to burn the fuse. Lightning has already beat its way through every available transistor before the fuse begins to heat.

Where are you going to find 15 amp coils?

Sounds to me you want to place your custom OVP next to your computer which will make it not work no matter how well it is made.

Install a surge suppressor and surge capacitor from DeltaLA into your grounded breaker box and be done with it. Anywhere other than the breaker box will not work.

[Behemot]

Re: What's inside overvoltage protectors?

Who said it will be dimensed for 15 A? I am not insane Anyway even in 1kW PSU's are filtering coils with still pretty thin wires, why do you think there would be a problem? I can still use more coils in paralel

Again I did not talked about lightning hitting the house, I said lightning hitting the power grid. There are breakers but still you can even see it on light bulbs when light hits high voltage power grid. So I can imagine what it makes to switching power supplies.

[delaware74b]

Re: What's inside overvoltage protectors?

FYI - most devices (outlets, switches, etc) will 'flash over' around 6KV. In theory, you 'only' need to protect from normal line voltage (120 in US) to the 6KV level.
The flip side of the 6KV is there really nothing that will absolutely protect you from lightning strikes, including the power grid. It can be 'directed' toward ground but goes wherever the path of least resistance.
I've seen the destruction when lighting hit the cable tv cable, went in the house through the cable modem/dv box, blow up the 'surge protector' back through the house wiring. It also followed the coax around the house to the cable company's excuse for a grounding point (bar clamp on the meter pan because they were too lazy or didn't have the split-bolt connector for the building ground which was less the 3 feet from the meter pan). Luckily, no fire, but lost all the electronics in the house and half the light bulbs were blown apart. They also had to replace bottom 3 courses of vinyl siding because the cable company tucked it under the siding and fire company ripped it all off to check to fire. The siding was burnt anyway....

[severach]

Re: What's inside overvoltage protectors?

Lighting on the grid. Same problem, same solution, in the breaker box only.

Lightning can be protected 100%. Radio, phone, and power companies do it all the time. There's just nothing that will protect 100% on a home budget. However if you do it right you can get 99% and that's a lot better than the negative % you get with a plug in surge suppressor. That's right! A plug in surge suppressor is worse than no suppressor at all. I cut all the MOVs out of my surge strips.

Diverting lightning strikes to ground away from protected equipment is easy when you know how. It requires two elements. The first is a short path to ground. The surge suppressors must be placed in the breaker box because that is the shortest possible distance to ground. Just a few feet of wire has so much impedance to a surge that other paths near your computer become almost as as desirable so a substantial portion goes through the computer. With the suppressor in the box as a short path to ground, the computer on the end of the long path to ground does not look very desirable to the surge. Almost all of it goes through the suppressor and almost none of it goes through the computer. While electricity does indeed take all paths, it takes all paths proportional to the difficulty of each one. Provide a hard and easy path and it will mostly take the easy path every time.

The arrangement can be beefed up with coils, longer wires, isolation transformers, isolated grounds, and bigger surge suppressors. But it's not really necessary because so much can be accomplished with what you already have just by adding a few low cost components at the right place. An isolation transformer is not necessary since to a surge it is no different than a very long wire. Just roll up a low cost extension cord if you want coils or a longer wire. The coil will have no effect on 50/60Hz power but will stop lightening surges dead so long as there is another path.

[Behemot]

Re: What's inside overvoltage protectors?

Interesting but I've bever said I want protections against light. I said I want protection against voltage spikes which appeares when lightning hits high-voltage distribution grid which happens sometimes since there is one of the greatest distributing stations in our country few clicks from our house.

This power grid is much better target for lightning and of course the distributing company has lightning arresters installed. So there is no 500 kV at our 230 V grid than but still something happens for short periods of time (in terms of ms). For blackouts there are input capacitors in PSU's, for high voltage spikes (kV) there will be my surge protector. Both this situations appear from time to time during storms.

I hope now it's clear what I'd like to do :-)