Understanding Surge Protector Specs: A Guide for the Computer Age

[Tom.G]

the MCOV voltage would add up becoming 320V+320V=640 V (and clamping voltage would further increase).

Yes, that would be the case; you could get twice the expected voltage line-to-line if the SPDs were rated at the line-to-line voltage and were connected line-to-ground. Also, your earlier posts seemed to indicate that the 240V 3-phase was not referenced to ground (which I found rather strange at the time and was cleared up in your post #61.) Since in reality you have 120V 2-phase, 120V SPD on each line would work. There are also 120v/240v SPDs for exactly that situation. But that would exceed the 300V limitation on the power supply input voltage. The only way to address the 300V limitation is to supply 120V to the power supply.

But why haven't you considered this?

Because that was not the question you asked. You asked in post #63 "computer is connected to Phase A and Phase B and the SPD is intended for Phase A and Ground."

As a side comment, I am not at all surprised that your attempt to return the already installed SPDs was rejected. The vendor has no way of knowing or testing if the have been damaged by a surge. Would you willingly buy a used protective device at full price knowing that it is in unknown condition? At least here in the USA, electrical and electronic components that have been installed are not returnable, for not only that reason but the vendor could be liable for any subsequent damage.

Cheers,
Tom

 

[kiki_danc]

Yes, that would be the case; you could get twice the expected voltage line-to-line if the SPDs were rated at the line-to-line voltage and were connected line-to-ground. Also, your earlier posts seemed to indicate that the 240V 3-phase was not referenced to ground (which I found rather strange at the time and was cleared up in your post #61.) Since in reality you have 120V 2-phase, 120V SPD on each line would work. There are also 120v/240v SPDs for exactly that situation. But that would exceed the 300V limitation on the power supply input voltage. The only way to address the 300V limitation is to supply 120V to the power supply.

Because that was not the question you asked. You asked in post #63 "computer is connected to Phase A and Phase B and the SPD is intended for Phase A and Ground."

As a side comment, I am not at all surprised that your attempt to return the already installed SPDs was rejected. The vendor has no way of knowing or testing if the have been damaged by a surge. Would you willingly buy a used protective device at full price knowing that it is in unknown condition? At least here in the USA, electrical and electronic components that have been installed are not returnable, for not only that reason but the vendor could be liable for any subsequent damage.

Cheers,
Tom

Oh I haven't thought of it that supplier won't accept the product for return because it may suffer a bit of surge damage already.

Anyway you haven't answered this question:

So the above will work only at increased clamping voltage. Ok. But I was asking if the surge would be dissipated by the current going to the ground or the MOV element just heating up... what do you think?

 

[kiki_danc]

Here's an interesting experiment in the paper at http://www.surgesuppression.com/ima...licationofSurgeSuppressionRevDate10202005.pdf

Power was applied to Phase A and B and thermometer was used to measure the temperature of the MOV when surge was introduced (details in the paper above).

Based on the much higher temperature rise in the discrete line-to-line MOV, the discrete line-to-line MOV absorbs a much larger portion of the surge current and energy than the combination of the two line-to-neutral paths.

In the experiment, why did the MOVs heat up in the 2 element Phase A to ground & Phase B to ground MOVs (instead of just the 1 discrete line to line MOV).. is the current of the 2 element series not shunted to neutral? I assume neutral is same as ground.

If the neutral were made ground.. would the results be the same?

And lastly if there was no discrete line to line MOV used.. what would be the behavior of the 2 elements MOV in series (the Phase A to ground and Phase B to ground MOV).. would it behave less than discrete line to line or similar in shunting the current? What do you think?

Knowing the answers above would wrap up my questions about SPD and end up this thread once and for all. Lol.

 

[kiki_danc]

Here's an interesting experiment in the paper at http://www.surgesuppression.com/images/DotNetSite/TechPapers/ModesofProtectionwithinElectricalSystemsforApplicationofSurgeSuppressionRevDate10202005.pdf

View attachment 231382

View attachment 231383Power was applied to Phase A and B and thermometer was used to measure the temperature of the MOV when surge was introduced (details in the paper above).

Based on the much higher temperature rise in the discrete line-to-line MOV, the discrete line-to-line MOV absorbs a much larger portion of the surge current and energy than the combination of the two line-to-neutral paths.

In the experiment, why did the MOVs heat up in the 2 element Phase A to ground & Phase B to ground MOVs (instead of just the 1 discrete line to line MOV).. is the current of the 2 element series not shunted to neutral? I assume neutral is same as ground.

If the neutral were made ground.. would the results be the same?

And lastly if there was no discrete line to line MOV used.. what would be the behavior of the 2 elements MOV in series (the Phase A to ground and Phase B to ground MOV).. would it behave less than discrete line to line or similar in shunting the current? What do you think?

Knowing the answers above would wrap up my questions about SPD and end up this thread once and for all. Lol.

​

Since MOV can be used between line to line as indicated in the paper above.. I wonder what would happen in the following if one of my 320 Vac MCOVs (instead of two) were put between the 120 volts line:

Of course I won't try it (I'm not crazy to experiment). Just want to know what theoretically would happen.. would it explode? Or work in a while then shuts down? etc.

 

[Tom.G]

This is in response to your post #72. I must have forgotten to click the POST REPLY button before I went off-line for a while.

Another case of insufficient information or under specified condition. You show a 3-phase transformer without a Ground or Common connection, in an earlier post you specified 3-phase 240V with 120V to a Common. Here the 3 lines are labeled 120Vac but your earlier posts stated the transformer windings as 240V. When measuring 120Vac on this diagram where is the other voltmeter lead placed?

 

[kiki_danc]

The other voltmeter lead is placed in the ground lugs of the panel which is simply connected to the Earth or soil. Our power company doesn't have separate ground or neutral. My service entrance has only 3 wires (3 phase) coming to the building.. we provide our own ground by sticking it to earth. I'm sure of this because I inquired from the power company years ago.

Anyway, the 120 volt thing has opened the floodgates in that I can now access all of amazon products which are based on 120 volts. Before I had difficulty finding supplier.. and only found one prosurge distributor locally. Now I can buy for example $69 Prosurge at amazon like https://www.amazon.com/dp/B012IR9Q2K/?tag=pfamazon01-20

My supplier sold the 240 volts version at more than $100. At amazon the 120 volts same specs is only $69. Now I am curious about something. In the United States.. you have Line to Neutral of 120 volts.. and you use it to power your appliances.. if you have 3 phase there.. is it also 120 volts per phase.. meaning if you connect phase to phase.. then it's also 240 volts? I wonder if the US and my place has same power transformers and only the tapping differs. And does it matter if the ground is provided in the transformer or in the soil. Our power company simply doing cutting costs by saving the ground in the transformer and we need to provide ourselves.

I'm asking you this since you can describe it from the perspective of what I mentioned in this thread. Also I think I'd better get a line to line SPD. I saw this at amazon. https://www.amazon.com/dp/B0052NKYC4/?tag=pfamazon01-20
Siemens TPS3A03050 120/240 Type 1 Split Phase Surge Protective Device Lightning Arrester Replacement

In the US. Is there a 120/240 split phase power system? Is it the same as the Delta with 120 volts per phase in my place (and 240 volts line to line)?

I promise this is the last level of inquiry as I don't want to get so much of your time. And as a way of saying thanks.. I can give you my 240 volts prosurge if you need it.. lol
​

 

[Tom.G]

Reference your post #73.

In the experiment, why did the MOVs heat up in the 2 element Phase A to ground & Phase B to ground

Remember that the MOV's act like a resistor when they conduct, their voltages rise as their current increases. The 300V sum of the 2 MOV voltages is close to the 320V of the line-to-line MOV. With the voltages being so close they are sharing the current.

is the current of the 2 element series not shunted to neutral?

The current DIFFERENCE between the 2 elements would typically be shunted to Neutral (which is usually Ground). For instance if one of the MOV's conducted 100A and the other 120A, then 20A would typically flow thru the Neutral lead. There is not enough detail of the test setup nor is it known to me if your Neutral/Common is indeed connected to Ground, and if so what the current capability is of that connection.

If the neutral were made ground.. would the results be the same?

Similiar, see previous comment.

if there was no discrete line to line MOV used.. what would be the behavior of the 2 elements MOV in series (the Phase A to ground and Phase B to ground MOV).. would it behave less than discrete line to line or similar in shunting the current? What do you think?

Similiar... but then you have the situation of when one fails you have no protection on that line.

Cheers,
Tom

 

[Tom.G]

EDITS in Blue. (Must remember, not after midnite!)

In the United States.. you have Line to Neutral of 120 volts.. and you use it to power your appliances.. if you have 3 phase there.. is it also 120 volts per phase.. meaning if you connect phase to phase.. then it's also 240 volts?

For single family and most multi-family residential the service 120/240V split phase; that is the transformer secondary on the power pole is 240V center-tapped, with the center tap (CT) conneced to Earth at the transformer and also brought to the building with the two 120V wires, where the CT is called Neutral. This Neutral is also grounded at the circuit breaker box with a large wire connected to a long metal rod driven into the Earth. Large appliances, such as an electric stove, are connected to all three wires, making both 120V and 240V available.

In the US. Is there a 120/240 split phase power system? Is it the same as the Delta with 120 volts per phase in my place (and 240 volts line to line)?

Yes, it is available. It is usually used for larger buildings as a way to balance the load across the 3 phases that the power company supplies. At the point of use it is treated as 3 separate supplies, sometimes with a separate electric meter for each.

There is also 120/277V 120/208V 3 phase available for larger multi-family residential and medium industrial. These transformers have 120V secondaries connected in the Wye (or Star) configuration, making a 4 wire supply. The common point (Neutral) of the three secondaries is connected to Earth, brought to the building, and Earthed at the breaker box. 120V is available from any phase to Neutral, and 277V 208V is across any two phases. The 120V is used for the usual wall outlets, etc. The lighting is often 277V single phase fluorescent fixtures, and the 277V 208V 3 phase is for large motors, etc.

Larger industrial typically is supplied with 480V 3 phase, but I don't now the details of that configuration. either Delta or Wye connected. The Wye connected supplies 277V phase to Neutral and 480V across phases. The lighting is often 277V single phase fluorescent fixtures. There would be an on-site transformer to supply 120/240V split phase for wall outlets, etc. (Must have a coffee maker, you understand!)

Thanks for the Prosurge offer, but I have a 120/277V 120/208V service here so it wouldn't be a good fit. Keep it around you may have a use for it, (maybe even next month. who knows!)

Cheers,
Tom

p.s. What is that 24VDC power supply supplying power to?
p.p.s The breaker box photo with the 3 phase breakers must be connected to three split phase transformers somehow.

 

[kiki_danc]

p.s. What is that 24VDC power supply supplying power to?
p.p.s The breaker box photo with the 3 phase breakers must be connected to three split phase transformers somehow.

​

The 24v dc is connected to a very sophisticated security system with cctc, motion detectors, fire panels, gsm dialers etc

Yes the 3 breakers are connected to each of the 3 phase wire entering the buildings.

So if i buy the siemens 120/240 split phase spd with discrete line to line protection. It should be compatible to my delta 3 phase with 120v each phase?

Reference your post #73.
View attachment 231389Remember that the MOV's act like a resistor when they conduct, their voltages rise as their current increases. The 300V sum of the 2 MOV voltages is close to the 320V of the line-to-line MOV. With the voltages being so close they are sharing the current.The current DIFFERENCE between the 2 elements would typically be shunted to Neutral (which is usually Ground). For instance if one of the MOV's conducted 100A and the other 120A, then 20A would typically flow thru the Neutral lead. There is not enough detail of the test setup nor is it known to me if your Neutral/Common is indeed connected to Ground, and if so what the current capability is of that connection.

In normal power system like in US single phase supply.. when the SPD short circuits to ground.. I thought all the current would go to ground.. isn't it this is the purpose of SPD being connected to ground... where all current would go. In the above experiment, let's say the neutral is connected to ground and have enough wire size.. isn't it the 100A conducted in one would go to the ground? Why did you say only 20A goes to the ground? Also the 2 phase is 120 degree out of phase like in the following:

so when one is conducting.. the other may not.. or you mean they conduct at same time? But why the 20A difference?

Similiar, see previous comment.Similiar... but then you have the situation of when one fails you have no protection on that line.

Cheers,
Tom

The experiment seems to be saying that discrete line to line SPD protection is more effective.. why do you say it's the same? The paper comments on the paragraph about it that:

"In contrast, if an SPD with only seven modes of protection is utilized for the same system and the line-to-line protection mode is proteced by the series combination of the line-to-neutral and neutral-to-line modes or the line-to-ground and ground-to-line modes, then those modes (line-to-neutral or line-to-ground) are intentionally exposed to unnecessary and undesired transient voltages. In essence, the SPD is sharing the line-to-line transient with the line-to-neutral and line-to-ground modes and creating voltages on those modes that would not be present with the use of a discrete all mode protection SPD."

​

What would happen if the ground to neutral is intentionally exposed to unnecessary and undesired transient voltages?

For general line to line protection.. do they use dedicated line to line SPD (without ground but heating the element) or do they use line-to-ground and ground-to-line like in my setup? I want to know if my existing setup is common or not.

 

[Tom.G]

See corrections to my post #78 https://www.physicsforums.com/threads/surge-protector-specs.955697/page-4#post-6064607

(Amazing the things you think of while falling asleep.)

 

[kiki_danc]

Tom. Thanks to you the supplier and distributor have decided to send me a 150Vac SPD for free (after they realized we are right the clamping voltage can increase).. but then I'm having second thought.. I plan to get the Siemens 120/240V split phase at amazon with protection mode that includes L-L. As detailed in my last message, Protection mode that include L-L is more superior than the series connections of two spds, right?

And before I order. I'm verifying if my transformers are really Delta or Wye. Looking at file photos. I found out there was a neutral or ground entering the busbar (white wire among the 3 big black).

This is my actual transformers (some details faded for security).

The two transformers tap to only 2 high tension wires above it, the 3 phase wire entering my service entrance is from the A, B and C terminals. The right transformers has label "x1", "x2", and "x3". So it comes from "x1" and "x3" while on the other side, the terminal C is from "x1".

Do you recognize the transformers as Wye or Delta?

And if I order the Siemens 120/240v split phase at amazon.. it should be compatible by only tapping to the 2 phase of the 3 right? (since I'd just use the admin breaker for the surge protectors and not the full 3 phase breakers).

https://www.amazon.com/Siemens-TPS3A03050-Protective-Lightning-Replacement/dp/B0052NKYC4/ref=sr_1_1?ie=UTF8&qid=1538355017&sr=8-1&keywords=siemens+120/240v+split+phase

Hope to order it soon and done with all this so we can focus back on string theory... lol.. my electrician will install the Siemens don't worry. Thank you.

 

[Tom.G]

Protection mode that include L-L is more superior than the series connections of two spds, right?

Right.

The two transformers tap to only 2 high tension wires above it

With only 2 high tension wires and 2 transformers I fail to see how there can be 3 phases. At a minimum you need a wire and transformer for each phase. Can you supply a sketch of the the wiring for both the primary and secondary of the transformers? For instance there has to be at least 2 terminals wired for both the primary and secondary of each transformer.

I found out there was a neutral or ground entering the busbar (white wire among the 3 big black).

Yes, it looks like the busbar box in the photo already has 120V going thru it. That's the Blk, Wht, Grn trio in the lower right. Wht = Neutral, Blk = Hot, Grn = Earth Ground. Why are you resisting using the existing 120V for the 24VDC power supply? Or even a control transformer to step the 240V down to 120V? After all, the time spent so far already exceeds the cost of a control transformer by a big margin.

 

[kiki_danc]

Right.

With only 2 high tension wires and 2 transformers I fail to see how there can be 3 phases. At a minimum you need a wire and transformer for each phase. Can you supply a sketch of the the wiring for both the primary and secondary of the transformers? For instance there has to be at least 2 terminals wired for both the primary and secondary of each transformer.

Yes, it looks like the busbar box in the photo already has 120V going thru it. That's the Blk, Wht, Grn trio in the lower right. Wht = Neutral, Blk = Hot, Grn = Earth Ground. Why are you resisting using the existing 120V for the 24VDC power supply? Or even a control transformer to step the 240V down to 120V? After all, the time spent so far already exceeds the cost of a control transformer by a big margin.

No. The Green black, white wires in the lower right are connected to another breakers below. I bought green wires 5 years ago because there was no other colors on stock. During installation, the electrician said green is for Earth ground but I already bought 30 meters and it's already cut. So they are not separate power from outside.. but just half meter wires to be connected to a meter below it and breaker and to another room.

Well. In my place all most use line to line of 240 volts. It's rare to use 120 volts. So our neutral or ground is virgin. If I connect the line to ground (of course after asking permission from city hall). And in other floors my hands touch the ground, won't I be jolted by electricity?

My solution is to add a type 3 to the equipments so the 1200 volts or so VPR in the type 1 or 2 would be lowered to 220 volts. This is better solution because remember I have 6 meters wire connecting from type 1 or 2 to equipments.. those can increase the voltage beyond 300 volts..

I'll find the explanation of how they can make 3 phase from 2 wires from high tension wires and 2 transformers and post it later.

 

[kiki_danc]

No. The Green black, white wires in the lower right are connected to another breakers below. I bought green wires 5 years ago because there was no other colors on stock. During installation, the electrician said green is for Earth ground but I already bought 30 meters and it's already cut. So they are not separate power from outside.. but just half meter wires to be connected to a meter below it and breaker and to another room.

Well. In my place all most use line to line of 240 volts. It's rare to use 120 volts. So our neutral or ground is virgin. If I connect the line to ground (of course after asking permission from city hall). And in other floors my hands touch the ground, won't I be jolted by electricity?

My solution is to add a type 3 to the equipments so the 1200 volts or so VPR in the type 1 or 2 would be lowered to 220 volts. This is better solution because remember I have 6 meters wire connecting from type 1 or 2 to equipments.. those can increase the voltage beyond 300 volts..

I'll find the explanation of how they can make 3 phase from 2 wires from high tension wires and 2 transformers and post it later.

I'm sure it's 3 phase from 2 transformers. I used binocular to look at the wires. The wires are tangled so I can't tell the details. But the following is one explanation of how to get 3 phase from 2 transformers.

http://forums.mikeholt.com/showthread.php?t=144067 (better source.. )

https://www.diy-forums.com/threads/three-phase-from-2-transformers.279495/

 

[kiki_danc]

I'm sure it's 3 phase from 2 transformers. I used binocular to look at the wires. The wires are tangled so I can't tell the details. But the following is one explanation of how to get 3 phase from 2 transformers. https://www.diy-forums.com/threads/three-phase-from-2-transformers.279495/

If you will google "3 phase from 2 transformers".. many explanations would come out.. for example:

http://forums.mikeholt.com/showthread.php?t=144067

best explanation in the following from above.. "It's called "open delta". If you Google this term, you will get all kinds of info.

"Picture three transformers providing 240/120V 3� 4W service that you mention. Now remove one not center-tapped. The voltage and phase across the terminals where the removed transformer was formerly connected is still the same.

BTW, POCO's still do this. "

here it says "open delta".. so I guess it answered what kind of transformers I have.. an open delta.. btw.. are you an electrical engineer?

 

[Tom.G]

Yes, I looked at the link you first posted and the links in it. They are all talking about using 2 transformers fed from a 3 phase generator and 3 phase distribution system. That's 3 phases with a 120° phase shift between them on three wires. You stated there are 2 wires in the high tension distribution side, not 3. Even the wikipedia diagram about half way down the page shows a 3 phase supply. How can you receive three different phases on 2 wires? There is only on way to connect a meter or transformer to them

 

[kiki_danc]

Yes, I looked at the link you first posted and the links in it. They are all talking about using 2 transformers fed from a 3 phase generator and 3 phase distribution system. That's 3 phases with a 120° phase shift between them on three wires. You stated there are 2 wires in the high tension distribution side, not 3. Even the wikipedia diagram about half way down the page shows a 3 phase supply. How can you receive three different phases on 2 wires? There is only on way to connect a meter or transformer to them

There are 3 high tension wires above it.. but there is only one terminal per transformer.. I can't see where the third one taps to... where should it be theoretically? Maybe you can find the third wire?

 

[kiki_danc]

There are 3 high tension wires above it.. but there is only one terminal per transformer.. I can't see where the third one taps to... where should it be theoretically? Maybe you can find the third wire?

View attachment 231459

I think I found the third wire.. it's tapped to small terminal (shown in red lines) at left transformer (connecting to the front most high tension wire)… the 2nd is hidden.. the rear high tension wire is connected to the terminal at right transformer

Whatever. It's an Open Delta Transformer.. so the Siemens 120/240V split phase is compatible by connecting to the 2 phases of 3? If yes. I'll order at amazon now and be done with all of this :)

 

[kiki_danc]

I think I found the third wire.. it's tapped to small terminal (shown in red lines) at left transformer (connecting to the front most high tension wire)… the 2nd is hidden.. the rear high tension wire is connected to the terminal at right transformer

View attachment 231460

Whatever. It's an Open Delta Transformer.. so the Siemens 120/240V split phase is compatible by connecting to the 2 phases of 3? If yes. I'll order at amazon now and be done with all of this :)

reviewing my electrical plans.. my wires in admin breaker is 8mm^2 and ground is just 3.5mm^2 to main circuit breaker... so I can't use line to ground because the ground wire size is made smaller because we always use line to line in my place. Anyway in the US.. when you connect line to neutral and get 120 volts.. and you touch the neutral wires in other places in the building or room. won't you get electrocuted? So I'm thinking if I really connect line to ground.. and touch other ground wires.. I may get electrical shock? no?

Whatever, the siemens 120/240V split phase is good to go.. isn't it.. when it's written protection mode includes L-L.. I assume it uses discrete MOV that heats up instead of moving the current to ground.. (?)

 

[Tom.G]

Yes, the Red looks to be the long-lost third wire. And the diagram in post #85 is similar to what I suspected when you said only 2 wires, I just wasn't familiar with the Open Delta configuration. (I learned something new. GREAT!)

But I still don't comprehend why you won't supply 120V thru a transformer to the 24VDC supply. The 240V SPDs won't keep the spikes below the 300V input rating of the supply. That was a limitation you stated earlier in the thread. Can you explain?

Cheers,
Tom

 

[kiki_danc]

Yes, the Red looks to be the long-lost third wire. And the diagram in post #85 is similar to what I suspected when you said only 2 wires, I just wasn't familiar with the Open Delta configuration. (I learned something new. GREAT!)

But I still don't comprehend why you won't supply 120V thru a transformer to the 24VDC supply. The 240V SPDs won't keep the spikes below the 300V input rating of the supply. That was a limitation you stated earlier in the thread. Can you explain?

Cheers,
Tom

I just talked to the power company electrical engineering team. They explained to me that it's government compliance.. back in the 1990s they received order from government never to use line to ground.. this is promote local manufacturers who produced 220 volts appliance.. because if we can use 120 volts.. we could order stuff from the US and our country would lose revenue..so they never allow any applications to be tapping from line to ground.. only line to line.. and if city hall inspect and saw our connection has line to ground.. we may be cited for violation. I guess this answered your question. But then you haven't answered.. if the US 120 volts line connect to ground.. and you touch the ground.. why don't you get electrocuted?

I also asked about the transformer. They confirmed it's Open Delta for 2 transformers of 75 Kva and below. When the usage increases above 150 Kva, then they change to 3 piece WYE transformers..

But if I'll have 220Vac SPD type 3 near equipment cascaded to the 220Vac SPD type 2 at breaker with 220 volts supply.. won't the voltage be below 300 volts? Well.. even if the residual VPR at type 2 is say 3000 volts.. won't it decrease down to 220 volts at the type 3 end?

 

[Tom.G]

That's an interesting explanation of 'No 120V'. It even sort of makes sense. What country are you in?

But then you haven't answered.. if the US 120 volts line connect to ground.. and you touch the ground.. why don't you get electrocuted?

Because the Neutral at the transformer is grounded, AND that Neutral is brought to the breaker box where it is also grounded, AND the Green Earth 'Ground' wire is also connect to Neutral at the breaker box. If the 120V shorts to Ground it is the same as shorting to Neutral, the short essentially short-circuits the transformer and the circuit breaker trips.

For supplying the 24VDC supply, if you use a transformer connected to 240V you are meeting the non-120V requirement and getting the opportunity of better protection for the 24VDC supply. If you have an electric doorbell, it likely runs on about 16VAC from a transformer, which makes it comply with the 240V requirement.

Cheers,
Tom

 

[Tom.G]

That's an interesting explanation of 'No 120V'. It even sort of makes sense. What country are you in?

But then you haven't answered.. if the US 120 volts line connect to ground.. and you touch the ground.. why don't you get electrocuted?

Because the Neutral at the transformer is grounded, AND that Neutral is brought to the breaker box where it is also grounded, AND the Green Earth 'Ground' wire is also connect to Neutral at the breaker box. If the 120V shorts to Ground it is the same as shorting to Neutral, the short essentially short-circuits the transformer and the circuit breaker trips.

For supplying the 24VDC supply, if you use a transformer connected to 240V you are meeting the non-120V requirement and getting the opportunity of better protection for the 24VDC supply. If you have an electric doorbell, it likely runs on about 16VAC from a transformer, which makes it comply with the 240V requirement.

Cheers,
Tom

 

[kiki_danc]

That's an interesting explanation of 'No 120V'. It even sort of makes sense. What country are you in?Because the Neutral at the transformer is grounded, AND that Neutral is brought to the breaker box where it is also grounded, AND the Green Earth 'Ground' wire is also connect to Neutral at the breaker box. If the 120V shorts to Ground it is the same as shorting to Neutral, the short essentially short-circuits the transformer and the circuit breaker trips.

For supplying the 24VDC supply, if you use a transformer connected to 240V you are meeting the non-120V requirement and getting the opportunity of better protection for the 24VDC supply. If you have an electric doorbell, it likely runs on about 16VAC from a transformer, which makes it comply with the 240V requirement.

Cheers,
Tom

You mean using the 150Vac SPD at the secondary end of a 220V primary & 120 volt secondary transformer? I haven't thought of that. But I guess the transformer may not fit inside the circuit panel. And you will have long lead wires enough to bring VPR up high back to 220 volt reference level. If you will put the transformer near the equipment.. you mean using 320 Vac SPD at breakers and 150 Vac SPD at equipment?

 

[Tom.G]

Yes, that's what I was trying to say in post #62 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-4#post-6064111).
320V SPD at transformer primary and 150V SPD at the equipment. Doesn't matter where the transformer is physically placed.

And you haven't answered... What country are you in?

 

[kiki_danc]

Yes, that's what I was trying to say in post #62 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-4#post-6064111).
320V SPD at transformer primary and 150V SPD at the equipment. Doesn't matter where the transformer is physically placed.

And you haven't answered... What country are you in?

By 320V Spd at transformer primary, you mean two 150Vac SPD in series (for phase a to ground and phase b to ground we discussed earlier) giving total of 300Vac.. or maybe you mean line to line 320V SPD. I'd prefer the latter because the former is artificial. In the US, you have hot wire to neutral so it's natural to put one SPD to ground. But for line to line... creating two SPDs in series with ground at middle is kinda artificial.. isn't it. So I need to buy a line to line SPD at breaker.

For the equipment. Since I'd cascade type 3 SPD to type 3 at breaker, voltage from type 3 would be further suppressed to 220 volts.. so why do I have to use transformers.. problem is.. if the transformer gets defective, the MOV element may end up in flame.. Also if you use transformers.. the 120 volts line to ground would become 60 volts.. and there is no 60 volts SPD.. if you use 150 volts SPD just one piece.. it won't work.. it must be two piece since you are protecting line to line... or the new illustration for the transformer secondary end...

I'd msg you in prv for the country for security reasons.

 

[kiki_danc]

By 320V Spd at transformer primary, you mean two 150Vac SPD in series (for phase a to ground and phase b to ground we discussed earlier) giving total of 300Vac.. or maybe you mean line to line 320V SPD. I'd prefer the latter because the former is artificial. In the US, you have hot wire to neutral so it's natural to put one SPD to ground. But for line to line... creating two SPDs in series with ground at middle is kinda artificial.. isn't it. So I need to buy a line to line SPD at breaker.

For the equipment. Since I'd cascade type 3 SPD to type 3 at breaker, voltage from type 3 would be further suppressed to 220 volts.. so why do I have to use transformers.. problem is.. if the transformer gets defective, the MOV element may end up in flame.. Also if you use transformers.. the 120 volts line to ground would become 60 volts.. and there is no 60 volts SPD.. if you use 150 volts SPD just one piece.. it won't work.. it must be two piece since you are protecting line to line... or the new illustration for the transformer secondary end...

View attachment 231462

I'd msg you in prv for the country for security reasons.

If I'm right above that there is no lower than 150 Vac MCOV SPD (the label at right must be 150 instead of 120) and it can't work. Then the only solution is to buy 2 Siemens 120/240V split phase type 1. However, I'd use it as type 2 and type 3. So I guess this will solve all.

Hope you can state now if you don't have adverse comment so I can proceed and finally leave this thread behind. I'm been occupied for this for a week and away from string theory and I feel guilty. Thanks so much Tom.

 

[Tom.G]

Since I'd put type 3, voltage from type 2 would be further suppressed to 220 volts

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

 

[kiki_danc]

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

What? You mean even if the output of type 2 from breaker is 1200 volts VPR.. when this inputs into the type 3, it won't get lowered down? Remember the 1200 volts is the voltage output from type 2.. meaning it's the residual voltage instead of 6000 Volts... so when you have voltage that low already.. a type 3 can suppress it down to 220 volts.. Or to make an easier example.. supposed you stand alone type 2 has only surge of 1300 volts.. won't that stand alone spd suppress it down to 220 volts??

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

View attachment 231464

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

 

[Tom.G]

won't that stand alone spd suppress it down to 220 volts??

What does the datasheet say about the type 3 you are proposing? I've lost track of all of the ones we've discussed.

 

[kiki_danc]

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

View attachment 231464

This is the part that I want to understand from the beginning. If your power supply is line to line and your equipment is line to line.. how can common mode occurs when your equipment is not grounded.. and even if there is surge at line to ground.. how can it damage the equipment?

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

So in the primary. I'd put 320 Vac MOV across the 220 volts line to line.. and 150 Vac MOV from line 1 to ground and line 2 to ground? meaning I'd be using 5 pieces of 150 Vac MOV and one 320 Vac MOV?

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

What does the datasheet say about the type 3 you are proposing? I've lost track of all of the ones we've discussed.

Let's take this 320Vac SPD...

If the surge is 6000 volts, 3000 ampere at 8/20 microsecond.. VPR is 1200 volts...
However if the surge is only say 1300 volts.. 500 ampere at 8/20 microsecond.. won't the VPR become say 100 volts only or so?

Edit: I mean won't the voltage becomes 100 volts only or so way below the VPR rating?

 

[kiki_danc]

This is the part that I want to understand from the beginning. If your power supply is line to line and your equipment is line to line.. how can common mode occurs when your equipment is not grounded.. and even if there is surge at line to ground.. how can it damage the equipment?So in the primary. I'd put 320 Vac MOV across the 220 volts line to line.. and 150 Vac MOV from line 1 to ground and line 2 to ground? meaning I'd be using 5 pieces of 150 Vac MOV and one 320 Vac MOV?

Let's take this 320Vac SPD...

View attachment 231466

If the surge is 6000 volts, 3000 ampere at 8/20 microsecond.. VPR is 1200 volts...
However if the surge is only say 1300 volts.. 500 ampere at 8/20 microsecond.. won't the VPR become say 100 volts only or so?

Edit: I mean won't the voltage becomes 100 volts only or so way below the VPR rating?

See this illustration for the above...

So type 3 would only have very low voltage way below the VPR.. why is this wrong?

(also note the 420 V you were mentioning were really DC in the specs)

 

[Tom.G]

This is the part that I want to understand from the beginning. If your power supply is line to line and your equipment is line to line.. how can common mode occurs when your equipment is not grounded.. and even if there is surge at line to ground.. how can it damage the equipment?

Consider a nearby lightning strike that puts 6000V on the power line to ground. Much equipment is rated perhaps 600V or so from line to chassis, the the chassis is now at 6000V, and so is everything in it and connected to it. Is there anything near enough to the equipment that a 6000V spark can jump to? For instance the insulation in a transformer would likely break down if anything on its secondary is grounded or near a ground or a large conducting surface. If the transformer is mounted in an electrical box, the box would likely be grounded and the an arc would jump to the transformer core, to the box, to ground. If a person happens to be in contact with the equipment, he/she is now at 6000V; is the floor wet, person touching another piece of equipment at the same time?

So in the primary. I'd put 320 Vac MOV across the 220 volts line to line.. and 150 Vac Move from line 1 to ground and line 2 to ground? meaning I'd be using 5 pieces of 150 Vac MOV and one 320 Vac MOV?

This one I will back off from a bit, I tend to think how the wiring HERE is done. The SPDs you had installed in the breaker box were a very good start, leave them in. Now add a line-to-line SPD at the transformer primary.

Let's take this 320Vac SPD...

In line 4 of the table see "MCOV (VAC/VDC)" it says (320/420). That is saying you can put 420VDC on the input continuously and the device will ignore it, that it will not conduct.

Now go to line 7, "Voltage protection rating" "VPR" this shows "<1.2kV" meaning that the maximum clamping voltage is not greater than 1200V.

However if the surge is only say 1300 volts.. 500 ampere at 8/20 microsecond.. won't the VPR become say 100 volts only or so?

So type 3 would only have very low voltage way below the VPR.. why is this wrong?

That is an ASSUMPTION on your part. The manufacturer is only guaranteeing that the output is less than 1.2kV. How much equipment do you want to gamble that your assumption is more accurate than the manufacturers explicit statement?

Cheers,
Tom

 

[kiki_danc]

Consider a nearby lightning strike that puts 6000V on the power line to ground. Much equipment is rated perhaps 600V or so from line to chassis, the the chassis is now at 6000V, and so is everything in it and connected to it. Is there anything near enough to the equipment that a 6000V spark can jump to? For instance the insulation in a transformer would likely break down if anything on its secondary is grounded or near a ground or a large conducting surface. If the transformer is mounted in an electrical box, the box would likely be grounded and the an arc would jump to the transformer core, to the box, to ground. If a person happens to be in contact with the equipment, he/she is now at 6000V; is the floor wet, person touching another piece of equipment at the same time?

Thanks for this info. In my country, most electrician never connect metallic chassic to ground. They just cut the ground wire.. and before this week I didn't know the purpose was to trip the breaker in case line touches metallic chassic and not electrocute the person (most electricians ignore this). From now on. I'll ensure all metallic chassic is grounded.. we never did it before. Even the refrigerator in my house and aircon are not grounded at present.

This one I will back off from a bit, I tend to think how the wiring HERE is done. The SPDs you had installed in the breaker box were a very good start, leave them in. Now add a line-to-line SPD at the transformer primary.

The prosurge local supplier was afraid the 320Vac SPD may explode if put line to line 240 volts.. do you have reference it can be put line to line? I thought only line to ground.

In line 4 of the table see "MCOV (VAC/VDC)" it says (320/420). That is saying you can put 420VDC on the input continuously and the device will ignore it, that it will not conduct.

Now go to line 7, "Voltage protection rating" "VPR" this shows "<1.2kV" meaning that the maximum clamping voltage is not greater than 1200V.
That is an ASSUMPTION on your part. The manufacturer is only guaranteeing that the output is less than 1.2kV. How much equipment do you want to gamble that your assumption is more accurate than the manufacturers explicit statement?

Cheers,
Tom

That's why I want to understand the microscopic physics of MOVs. If you pass 1300vac voltage to it.. would it suppress the 1300vac to become 100 volts or would it become 1200vac? Understanding the microphysics may give us a clue.. so far what have you read about this?

 

[kiki_danc]

Thanks for this info. In my country, most electrician never connect metallic chassic to ground. They just cut the ground wire.. and before this week I didn't know the purpose was to trip the breaker in case line touches metallic chassic and not electrocute the person (most electricians ignore this). From now on. I'll ensure all metallic chassic is grounded.. we never did it before. Even the refrigerator in my house and aircon are not grounded at present.
The prosurge local supplier was afraid the 320Vac SPD may explode if put line to line 240 volts.. do you have reference it can be put line to line? I thought only line to ground.
That's why I want to understand the microscopic physics of MOVs. If you pass 1300vac voltage to it.. would it suppress the 1300vac to become 100 volts or would it become 1200vac? Understanding the microphysics may give us a clue.. so far what have you read about this?

Btw.. I assume you understand the difference between VPR and SVR (Suppressed Voltage Rating). Here is a brief summary in my own words. VPR is a UL 1449 Third Edition term, UL 1449 Second edition uses SVR (Suppressed Voltage Rating).
SVR is measured using surge pulse of 6000 volts, 500 ampere and 8/20 microsecond. The SVR output is about 400 volts. In UL 1449 third edition, they use surge pulse of 6000 volts, higher 3000 ampere and 8/20 microsecond producing 1200 volts let-through. That is why in 3rd edition, the 400 became higher at 1200 Volts. This proves that 1200 volts is the not the average or ceiling but only if the input is 6000V, 3000A at 8/20 us. If the input is just 6000 volts, 500 ampere at similar 8/20 microsecond, SVR becomes mere 400 volts. So I'm assuming if the input pulse is just 1200 volts, 1000 ampere at 8/20 microsecond, the SVR/VPR would be 100 volts. This is reasonable but like you said the manufacturing didn't test it at 1200 volts, 500 ampere input. Hmm... Maybe to be safe, you have the point about using 120 volt AC.

About leaving the original as it is. Remember the 320Vac Mcov gets added twice to become 640 Vac (from 220 ac line to line).. so it starts to clamp at 640 Vac. Shouldn't I use 150 Vac Mcov instead? If it clamps at 640 Vac.. VPR or SVR would increase too... why do you say retain it... you are relying on the secondary 120 volts to lower it?