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3rd LCD monitor broken, UPS without ground?!

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August 16, 2009 7:06:12 PM

I currently live in Thailand. My first PC died in one weak without a UPS.

Now I have a new PC with a UPS and it has been working for 5 months without problems.

However my LCD screen started giving me troubles and after 2 months I bought a new one. The new one died in 1 day. I got a replacement the next day and this one is also breaking down on me already.

the PC and monitor are both connected to a UPS but this UPS is connected to the electra without a third ground pole.

The power supply is Thailand is very bad. It isn't stable like it is in Holland where I come from. However everything here works on it, sure internet cafe's do have a third wire for the ground but everybody watches his TV without one.

Could it be this causes my LCD monitors to break down? Why can a TV run without a ground and a LCD monitor not?

Also as soon as I connect my monitor cable to my videocard there is a high amount of static electricity in my pc, is this normal? It occurs when nothing else is connected to my pc like the power cable or mouse etc, just the vga cable. I put it in and I start getting little shocks when I touch my cooler or harddrives. Is this normal or has it to do with there not being a ground connection for the UPS?
a b B Homebuilt system
August 16, 2009 8:47:56 PM

Quote:
Also as soon as I connect my monitor cable to my videocard there is a high amount of static electricity in my pc, is this normal? It occurs when nothing else is connected to my pc like the power cable or mouse etc, just the vga cable. I put it in and I start getting little shocks when I touch my cooler or harddrives. Is this normal or has it to do with there not being a ground connection for the UPS?
You shouldn't get shocks when touching components in your PC, but while it isn't desirable, it also isn't abnormal when there's no ground. Unfortunately it can cause component failures. What monitor do you have? Have you checked locally if there are monitors that work better under those conditions? You can't be the only one having that issue in Thailand if grounds are not used.

Is the TV connected to a cable that's grounded? If so, then you may be able to ground the UPS through that cable.
August 16, 2009 8:59:07 PM

If you have some wire, you can make your own ground by attaching your UPS's ground cable to a water pipe that goes down underground.
Related resources
a b B Homebuilt system
August 16, 2009 11:33:36 PM

frozenlead said:
If you have some wire, you can make your own ground by attaching your UPS's ground cable to a water pipe that goes down underground.
Good recommendation, unless they use plastic tubing. Regardless, the OP needs to figure out a way of grounding the UPS.
August 17, 2009 5:17:25 AM

Well first of all everybody sais you don't need a UPS or a ground cable over here. But when you go look around every computer store, internet cafe or business does have them.

I have found noone who has had the same problem with his screen, like I said everybody does run a TV here without a ground wire.

So I can probably get another new screen at the PC store and I am ashamed to death but what are the odds?!

I'm going to have a technician make a ground for me today, all I need to know is what you peeps think about it....

Is it likely that the 3 LCD screens I had went broken because the UPS isn't connected to a ground pole?

I mean it is so weird to me since my PC is running fine and my microwave is as well...

What makes LCD screens in particular so sensitive to this?
a b B Homebuilt system
August 17, 2009 5:33:47 AM

Your PC has power correction built into the PSU and large capacitors to help dissipate spikes, your power supply along with the power control circuitry on the motherboard is very capable of maintaining even power even with bad supply, the LCD screen does not have space for large capacitors or power control circuitry so it is more succiptable to having spikes that its caps cant absorb. For optimal power cleanness you need one of the AC-DC-AC UPS's that produces a true sine wave as its output.

For ideas of how to ground your setup take a look at the massive post by paperdoc
http://www.tomshardware.com/forum/268662-31-plugged-out...

Optimally it would be best if you could get a hard wired ground but jerry rigged grounds are better than no grounds at all.
August 17, 2009 6:45:08 AM

Technically you don't need a ground. In the US, all standard ground lines from an outlet are connected to the neutral line anyway - there's no main ground that any commercial power company has. It is nice to have, though, as it puts less strain on your hardware. Sure, PSUs are built with caps to correct the kind of interference that can occur with no ground, but capacitors aren't the most reliable of electrical components, and it's best not to test them.

The particular LCD you have must have a cheap (or bad) power supply integrated into it. LCDs run on DC power, so a ground is not necessary (the negative line replaces it - that's called a chassis ground) past the AC/DC converter (AKA the power supply).

Just out of curiosity, does your LCD have an integrated or external power supply? If it's external, is the DC line (the cable you connect to the LCD) have a choke (or two) on it?
a b B Homebuilt system
August 17, 2009 3:00:46 PM

Ground is NOT your only issue. From what you describe, your problem may be that different electrical outlets have different versions of "Neutral".

In North America (and, I suspect, in Holland) we use a household power supply system called "Grounded Neutral", in which power is supplied to a house on two "Hot" lines nominally at +120 and - 120 VAC, plus the Neutral line to return current. You can think of these this way: the two "Hot" leads are from opposite ends of the power supply transformer's secondary winding, and the Neutral is from the winding's center tap. (It may not actually be that way, but the simple view will suffice.) In Europe the supply is 220 to 240 VAC on the "Hot" lines, but I'm not sure whether they use a Grounded Neutral between two "Hots". Anyway, in North America the Neutral line is connected to a good earth Ground both at the transformer and at the household breaker box. In this way we establish a firm reference point of zero volts (compared to earth ground) for the Neutral line throughout the entire house.

I do not know the system in Thailand, but if they do not use this Grounded Neutral system it's possible to get into some weird voltages that change randomly over time. From what you write, I suspect that your computer is plugged into your UPS, and your monitor is plugged in somewhere else (not into the UPS). Thus each has its own separate power connection and it appears likely that there is no connection between the two. The result is the the "Neutral" lines of the two devices are free to "float" in terms of voltage independently of each other. This means that the two different "Neutral" lines may have significant voltages between them. Now, it is common in computers, amplifiers, monitors, etc. to use the metal chassis of the unit as BOTH the 0 volt reference for the circuit and the Ground. When you have a true Ground connection through the third wire to a good earth connection this is no problem. But when you have no external true Ground, this means the unit's chassis is actually at whatever voltage the Neutral line has, because it is often connected to the chassis. Then we take this unit (your monitor, say) and plug it into another unit (your computer) which has a similar wiring system but is connected to a different supply source. This can produce two problems. One is a situation you already experience: the computer exterior case suddenly is not at zero volts like it was before, because it is now connected to the Neutral of the monitor, and its Neutral supply was not grounded. You start getting shocks off the exposed metal cases of both units. This is a symptom of what can cause the other problem you are seeing. Because the two chassis are no longer at some well-established reference voltage (0 for Ground), the voltages on the "High" (signal) side in each device may get to be much higher than they were designed for, resulting in damage to the circuits. These excess voltages often vary randomly, but it only takes a very brief high voltage surge to damage a solid state circuit.

In house wiring systems with no third Ground wire there is another "worst case" possibility, and this is seen in lots of older homes in North America. In those systems the wires going out to each wall outlet are Hot and Neutral, of course, but there was no standard way to connect those two to the slots of the outlet. Moreover, the plugs on the end of cords had two blades exactly the same, so you can plug it in "right side up" or "upside down" because there is NO "right side". When you plug in any one device you have a 50% chance that the wall "Hot" will end up being the device's "Neutral". For this reason manufacturers cannot expose the internal metal chassis to the person on the outside if there is no Ground. But suppose you plug in two devices like this to different outlets. You can see that it would be easy to end up with the chassis of one connected differently from the chassis of the second, with a big voltage difference. To prevent that a design change to plugs and outlets was made decades ago. Even 2-prong fittings (without Ground) have blades of different sizes so that you cannot plug something in "upside down", and there is a standard that ALL outlets will be wired the same way (in North America, the wider blade is always Neutral).

So how to fix? Establishing your own good Ground by a rod properly installed deeply into the earth can help if ALL of your devices have 3-prong electrical cords with the Ground line attached to the units' chassis. This has limits, though. One is that this really only works to get every device in your system at the same "Neutral" voltage if they all have both Ground and Neutral connected to their respective metal chassis. The other is that you may be trying to establish with your computer wiring a Ground connection for many Neutral lines in your area, and that MIGHT be a big load on the wires you install. The surest way to avoid problem voltages caused by "floating" power sources is to power ALL of the devices in one system from the same source. So, for example, without a UPS you should make sure that all of your computer system is powered by ONE outlet from the wall, by using a multi-outlet power bar or two. Since you have a UPS whose output may be isolated from the wall power, you should be running ALL (or as much as possible) of your computer system from the UPS outlet, and very little directly from the wall. Things you don't have to run off this common UPS supply: anything that is powered by a little power "brick" with only two wires feeding to the device. These mini power supplies almost always have an isolation transformer in them to reduce the voltage; their output is completely independent of the wall supply, and the device they supply is designed to establish its "Neutral" side reference by its connection to the rest of your system.

Unfortunately, this advice means that your UPS needs to be big enough to supply power to several devices, and it will keep those devices powered (in a supply failure event) for a shorter time than if it were used solely to power the computer itself. However, it seems you are using the UPS not for sustained performance in a power failure, but for protection against transient power surges.

By the way, most UPS units actually do have a voltage surge (spike) protection circuit at their input side to protect themselves and, consequently, the connected load. But some do not. Does yours? These spike protection systems can actually be destroyed by bad voltage spikes but leave the UPS still supplying power. For that reason, many have some indicator to tell you whether the protection system is working or not. Does yours give you this sort of indication?
a b B Homebuilt system
August 17, 2009 3:16:01 PM

But if both the PC and the monitor are connected to the UPS, then they share a common neutral.
a b B Homebuilt system
August 17, 2009 3:22:03 PM

GhislainG said:
But if both the PC and the monitor are connected to the UPS, then they share a common neutral.


Exactly right, which is why I advised plugging those two (and maybe a few other components) into the UPS outlet. That would eliminate the danger of excessive voltages from unrelated floating neutrals. A true Ground is useful for other reasons like noise elimination, but that's a different discussion.

You were quite right earlier to point our that plastic water piping eliminates those pipes from use for a Ground. OP said he's having a technician install a Ground for him -hope the tech knows about your water pipe caution, and how to install a reliable Ground rod system if necessary.
a b B Homebuilt system
August 17, 2009 3:36:34 PM

Wow, nice job paperdoc! Are you an electrician or something?

What specific UPS do you have? Some of them run power straight through them and trickle charge the battery on the side, if you have one like that its not going to be absorbing spikes as well. Unfortunately from what i have seen in the US the price difference between one of those and one that runs AC-DC-AC and runs all the power through the battery is huge.
a b B Homebuilt system
August 18, 2009 2:37:05 PM

I'm actually an Industrial Chemist now working in product development and economic development. I learned house wiring years ago for my own home and small business, and I've worked on an amateur level with audio and video systems and broadcasting. In graduate school training 'way back I worked with lab electronic equipment which often was very sensitive to noise and stray voltages, so the role of power supply and grounding always was in the background.
November 2, 2009 6:06:28 AM

Hi paperdoc, I know this is an old thread, but actually i have a similar problem and i hope you can help.

I Live in Lebanon, and here we get TV Chanels through a central cable company delivered to every house using coaxial cables.
Recently I bought an LCD TV with PC Input, and here starts my problem, the LCD TV was connected to the TV Cable and working fine for almost 15 days when I decided to connect my Laptop to the LCD TV. I got a VGA cable and after connecting the cable to the LCD TV and when connecting the other side to the Laptop I git a "power sparkle" and then the LCD TV turned off and a bad smell came of it and it didn't work after.
I sent it for repair and replaced it with a samsung LCD TV. this time and without connecting the Laptop, after connecting the TV Cable to the LCD TV, the splitter installed in the house broke and we called the Cable TV Technician who suggested that the LCD TV has a problem and is giving more powerto the cable than it should and that's what caused the Splitter to burn out. and that it's better to replace the TV. so we did that and got a Panasonic instead. The TV worked fine when connected to the TV Cable but when connected (at the same time) to the laptop it smelled burn and the TV Cable (the coax cable) went on fire. now the TV is still working but i can't connect it at the same time to the Cable and to the Laptop. it works well separately (i.e either connected to TV Cable to watch tv or if i want to connect the Laptop I have to disconnect the cable first otherwise it will burn the coax cable).
Any clues why is this happening???
Thanks in advance
a b B Homebuilt system
November 2, 2009 6:11:12 AM

New. Thread.
a b B Homebuilt system
November 2, 2009 11:51:46 AM

As jbakerlent said, it should be a new thread.

Check if there's voltage between the splitter and the TV outlet ground. If there's voltage, then expect something to burn. There should be no or very low voltage between grounds.
a b B Homebuilt system
November 2, 2009 2:00:58 PM

I suspect strongly that you have the TV and the laptop plugged into different outlets. There may also be an issue with the cable signal system. From what you describe, this is not a simple matter of minor differences between Neutral and Ground, etc. You have very large voltages causing big currents that burn out components immediately.

I don't know the power system standards where you are, or even whether your particular location follows any standard design. So let's not assume anything and check several items.

1. Do you have a reliable Ground anywhere? The ideal is a long solid metal rod placed deeply into the earth, with a clean connection to a wire into the house that can be used as you "Ground Bus". In North America and elsewhere, many homes simply use the metal water supply pipe entering the house and clamp onto it just inside the floor where it first enters. It is a solid metal piece well buried in lots of length of earth for good contact. You just have to be sure there is no plastic pipe between the real earth outside and the connection point you establish. Where you are, that may or may not be available.

2. There is a real possibility you may have different devices plugged in "backwards". Many electronic devices are designed so that the Neutral line of the power supply cord actually is connected to the internal chassis and becomes the circuit zero volt reference point, aka "Ground" of the circuit. The potential danger comes if it is possible to plug the cord into the wall so that this "Neutral" wire is actually connected to the "Hot" side of the supply. In North America we've gone to a design of outlet and plug that prevents this. Most plugs now (but NOT ALL plugs on electronic devices) have two power blades of different widths. One is wider, and that must be the Neutral line. The outlet likewise has different slot sizes. The whole thing is set up so that the narrow (Hot) blade and slot is the same size as the older system for both slots. So if you have a modern plug with different blades and try to plug it into an older outlet with only smaller slots, it won't work. This prevents you from plugging in "backwards" by mistake. (There's also the problem in the older system that less attention was paid at the time of installation to which slot was which, and there are many older homes with no "standard" way of wiring the same-size slots in outlets.) So if you have plugs with different blades in some manner that are intended to connect only one way and you try to defeat that design, you can get it backwards. There is also the real possibility that the outlets where you are may have been wired wrong and the outlet itself is "backwards".

3. In that different-blade design system there are some variations that still preserve the safety of the design. A three-prong plug and outlet (two flat parallel blades and a round Ground prong) is hard to defeat. There really is only one way to plug that into the outlet. Even they use a wider blade for Neutral and a narrower blade for Hot. On devices that do not use a Ground connection and provide only two blades on the plug, we still have the Wide-for Neutral, Narrow-for-Hot system, so you still should only be able to plug in one way. You will, however, find 2-blade plugs with both in the Narrow size. Those are supposed to be used ONLY on devices that do NOT have any connection of either power cord lead directly to the device circuits. Typically these are systems that have a voltage-changing transformer as the first element in the internal power system so that the actual circuit is completely isolated from the power supply from the wall. An easy example to see is a printer that has a separate "power supply" box in the middle of the cord from wall to printer - its cord probably has only two identical blades that plug into the wall outlet.

4. Given all these design points to prevent mis-connection, there is still the possibility that the intent could be destroyed if the outlets are installed wrong. So let's do some testing. You will need a voltmeter that covers the power system you have - maybe 120 volts AC, or 240 volts AC - and it MAY have a resistance measurement capability, too. Then you'll need a long-ish extension cord. The plan is to choose one outlet as a reference point and call it the "correct" one as far a wiring is concerned, and then check whether other outlets in your place agree with it. At that one outlet, the voltage between the two power slots will be your system supply voltage, usually 120 VAC or 240 VAC, or slightly lower. Even if there's no third Ground hole in the outlet, the metal box itself in the wall will be Grounded only IF your system actually provides a true Ground connection at the outlet box. Measure the voltages separately from each outlet slot to the box and note what they are. In North America now we have a system called Grounded Neutral in which, at the breaker panel that supplies the house, the Neutral bus also is connected directly to the Ground. So at every outlet you can measure 120 VAC from Hot to Neutral slots, 120 VAC from Hot slot to Ground hole and metal box, and 0 VAC from Neutral slot to Ground hole and metal box. Where you are may well be different. With a "Floating Neutral" (i.e., not Grounded) voltages measured from either slot to metal box will be small and somewhat variable because there really is not complete circuit. You also will need some reference Ground connection, with a long-ish wire from it to where you are measuring.

5. OK, first test is the one GhislainG suggested. You can only do this if you have a Ground wire to use, because we're looking for voltages compared to a known Ground. Disconnect the cable from your TV and measure the voltage from its outer sheath to Ground. It REALLY should be zero. Now, measure voltage from the inner wire (with the signal) of the cable to Ground. It also should be VERY near zero - within a couple of volts. If either of these is NOT zero or close, the cable system has a problem.

6. Now, another version of GhislainG's test - this one for voltage from cable system to TV. This is in case the TV has no real Ground connection so that Item #5 is kind of a meaningless test. Disconnect the cable from the TV and stick a small short bare wire into the center hole of the TV's input connector. Measure the 4 voltages: from cable sheath to TV input connector outer threaded piece, and also to the middle point (the little bare wire you installed). Then measure also voltages from the cable's center wire to those same points. These all should be within a couple volts of zero. Anything more and the cable system has a problem, OR the TV power supply has a problem.

7. OK, lets pursue the possibility that the problem is supply to the TV. Two things to check if possible. First one is to check voltages from the TV "Ground" assumed to be the outer threaded part of the antenna input connector, and the real Ground if you have it. Without a real Ground for reference, you can't do this test. But if you can, the result should definitely be zero volts. Now, whether you can do this or not, IF you got a non-zero reading here, or IF you got a non-zero voltage from TV to cable in item 6 above, let's see if we can change that. Can you unplug the TV and turn its plug over to re-connect, thus reversing the TV's connection to the wall? Do that if you can and then re-do all those voltage measurements between the TV, the cable, and true Ground. If doing this removed any high voltage readings and got you to zero volts on all those places, you've found a big solution. If this worked, then either your TV was plugged in "backwards" or its outlet was wired "backwards".

8. Now, let's start checking outlets. You have chosen one outlet to be the reference one that is "correct". Plug your long extension cord into it and check the voltages at its end, compared to the outlet, so you know which slot on the end of the cord is supposed to be Hot, and which is Neutral. Go to the outlet that the TV was plugged into and compare its slots to the slots on the cord. You should get zero VAC from Hot to Hot, and from Neutral to Neutral. If your supply voltage system is 120 VAC, then you should see that from any Hot to any Neutral. If you see 240 VAC on a system that supplies 120 VAC, then you have connections to opposite sides of a 120 / 240 VAC dual voltage supply system. That is not supposed to be a problem, but it can be.

9. OK, let us suppose that so far we have no big voltages indicating trouble. The search proceeds. Now we need to check the power supply to the laptop machine. Do tests on its wall outlet similar to those done for the TV's outlet. Is it showing exactly the same voltages as the TV's outlet? If yes, just to be sure, try to make readings directly from one outlet to the other to be sure they are the same. But if not, you've found a source of trouble to work on.

10. Now, with the laptop disconnected from the TV, measure the voltage from the VGA cable's outer shell to the TV's "Ground" point - either the outer shell of the VGA input connector, or the outer threaded part of the cable input connector. This should also be zero volts. Anything more is a problem.

10. Solutions? There are basically two possible routes. One is to isolate one or more things from the house power supply via an isolation transformer, and this may be a practical solution for a few lower-power devices so that you can actually get such a device and afford it. The other is to find a way to power ALL the devices you are connecting together from ONE outlet, and then make sure every one of them is plugged in the "right" way so all those voltages that SHOULD be zero actually are. One way to do this is to plug everything into the output of ONE UPS unit, but that might require a large and expensive UPS. If you don't need to guarantee smooth uninterrupted power but just want to ensure all devices come off ONE common outlet, as multi-outlet "power bar", with or without a surge protector, will do that. (Oh, I suppose we should also recognize the third option: IF your tests tell you that one or more outlets are mis-wired "backwards" compared to the others, maybe the solution is to have those wiring errors fixed.) By the way, I forgot to ask: does your cable system include an amplifier box in the house? If so, consider it one of the may devices that need to come off the same power supply.
November 2, 2009 4:48:04 PM

I already opened a new thread, I am not sure whether I should pass there or continue here, for now I will answer here and in case i need to go there please let me know.

Back to the issue : Waw, that's too much to compile :)  Thanks a lot for analysis but before I try all these things, I would like to point you to some important things in case it changes the analysis.

1- the TV and Laptop are plugged into the same power outlet. I tried reversing the plug of the tv but same result.
2- There is no ground cable installed and it's not that easy to do that as I live in an appartment on the 4th floor.
3- the Tv cable system has amplifiers installed on every building and TV Cables are used to pass power to these amplifiers ( I heard it's about 50 volts).
4- power system is 220 Volts and we have two lines coming into the houses, 1 hot (220 volts) and the other neutral.
5- I tried to check the power coming out from the tv system with a screw driver test and it does light.

Thanks again for your time.

a b B Homebuilt system
November 4, 2009 3:15:43 AM

Yes, your new info changes lots! You already have done many of the tests I recommended. I'm not sure exactly what item 5 means - what did you check for voltage when you say "the power coming out from the tv system"? The phrase "screw driver test and it does light" suggests to me your testing tool is a glow lamp mounted inside a screwdriver handle, and it glows when it has a significant voltage across it. If that's the case, you should know that it will glow with voltages over maybe 40 to 50 volts, but not much below that, so you cannot check for low voltages.

Important point is your item #3. This says the cable itself carries a very significant voltage (maybe 50 volts, by rumor) between center wire and outer shield, and it is used to power the distribution amplifier on the building. I would guess that is a DC voltage, not AC, but your glow tester won't tell you that. That certainly can cause the TV's input circuits to burn out in certain conditions. I'm kind of surprised it works at all! If it really is just a DC voltage, a small-value capacitor (but rated for over 50 VDC) in each of the center wire and shield connections to the TV's input connector would block that and still pass the high-frequency TV signals. Trying to rig that on your own and still keep a good signal (because you'd likely create a big impedance mismatch) might be hard to do, but you could try - small capacitors are cheap. Alternatively, ask the cable company if they supply a DC voltage blocker to fix this kind of problem.

I'm not impressed with your cable guy. You say, "we called the Cable TV Technician who suggested that the LCD TV has a problem and is giving more power to the cable than it should and that's what caused the Splitter to burn out". If the DC power on the cable story is true, then the trouble is not power FROM the TV, The problem is power TO the TV FROM the cable, and the TV allows so much current to flow that the cable's current-carrying capacity is exceeded. It could have damaged the TV badly, too. My North American experience says there should never be those voltages on a cable, but I don't really understand the system you have there. We do have a way to send DC power up an antenna line to an amplifier, but the system also includes a little box between the powered cable and the TV that has those capacitors built into it so what enters the TV is ONLY the low-voltage TV signal, and none of the power for the amplifier.
November 14, 2009 4:48:44 PM

Hi, my apologies if what I'm going to post is now in the correct section, as I'm not exactly sure where else to post. I find you guys here in this forum have very good knowledge of power, especially neutral and grounding. I have a problem which I hope you guys can help me out

While using a MGE Pulsar UPS to connect to our system, which uses a 3 phase 3 wire system, we get the "DC bus too high on rectifier" error msg. This subsequently leads to the breakdown and failure of the UPS later. Our configuration is a transformer which steps down incoming 380~500V to 220V/200V and the star point is used as the earth reference in order for the RCCB/ELCB to be effective for the protection requirement. Input to the UPS now currently is 2 phase input, i.e phase to phase 220V

I would like to ask for advice how we should hook up the UPS to the 3 phase 3 wire system, so the UPS will not fail prematurely always. The UPS technician had mentioned the earth reference was also a neutral point, and provided 110V when using this point with a phase.He suggested to use this earth reference with a phase (110V) and a step-up transformer (to step-up from 110 to 220V), which we felt was ridiculous.

Our UPS (MGE Pulsar M3000RT, i.e. rated 3KVA) topology is On-line double conversion with automatic by-pass and power factor correction

Any info or insight will be useful, thanks in advance
a b B Homebuilt system
November 14, 2009 5:47:09 PM

I don't know where you live as I've never heard of a country where the voltage is not 120V or 230V. Can't you get a certified electrician to hook it up properly or buy a UPS that will work with your input voltage without having to use a transformer? I wouldn't assume that the UPS technician is wrong.
November 14, 2009 6:54:08 PM

Hi sorry if I created some confusion...my problem is actually with regards to industrial UPS used in my company project, which is design used for vessel based (3 phase 3 wire system)

The connection schematic is in the link below for clearer reference:
a b B Homebuilt system
November 14, 2009 7:02:07 PM

That link doesn't work for us.
a b B Homebuilt system
November 16, 2009 1:02:56 PM

I am NOT an electrician, and this one probably needs a tech who really does know the equipment. I'll contribute some thoughts.
1. There is a distinction between the power supply system for your application, and the way that supply is connected to the device (in this case, your UPS). It appears the building supply is about 500 VAC, and then there is a dedicated transformer to convert that to 220 VAC for your application. This unit's output is connected as a 3-Phase "Y" system with Grounded central point (Neutral). This provides 110 VAC between the Neutral and any one Hot line, and 220 VAC between any two Hot lines. The central point Neutral is Grounded to establish a reference point and, more importantly, to enable important safety features for the feed to the UPS and its loads.
2. Supply to the UPS is supposed to be about 220 VAC. You say it "uses a 3 phase 3 wire system", but then you say "Input to the UPS now currently is 2 phase input, i.e phase to phase 220V." For 3 KVA I would not expect a full 3-phase power supply. I suspect instead that you have 3 wires into the UPS which really are simply two Hot lines (from to transformer output phase connections) and a Ground / Neutral. You're not really using a 3-Phase connection, just a 220 VAC connection.
3. I see no reason why you would need to take a 110 VAC connection, step it up to 220 VAC with an isolation transformer, and then connect one end of that to Ground again (to establish the Grounded Neutral for safety). You already have a transformer that isolates your UPS from the building supply and uses a Grounded Neutral.
4. Are there other loads on the 3-phase transformer that steps voltage down from 500 VAC to 220 VAC? Is it possible those loads are causing power surges in the supply to the UPS?
5. If the error message is that the DC bus voltage is too high internally, I would check that the supply line is connected correctly. I looked at some specs for these devices at an Eaton site, and I see that many MGE Pulsar UPS models have multiple input terminals (presumably a multi-tap primary winding on the input transformer) to adapt to the available power supply. So it is important to connect the input to the right terminals so that the UPS circuit gets the right voltage to start with. If, for example, your supply from the step-down transformer is 230 VAC, but it is connected to terminals on the UPS designed for 210 VAC input, the UPS would be experiencing an input that is 20% over voltage.
6. Note that some of these UPS's also have ways to adjust the output voltage for your system requirements, so it is possible for someone to over-volt the UPS input and then still make the output come out OK as far as your PC's are concerned. So, if an adjustment is made to the UPS's input connections, make sure that its resulting output also is checked and adjusted, if necessary, to supply the computers' requirements.
November 16, 2009 4:21:59 PM

Hi Paperdoc,

thanks for your info; its very valuable & I really appreciate it a lot

Please see below my answer to your points
Point 1: You are absolutely correct; I believe this best explains the setup

Point 2: Yes the UPS is accepting simply 2 hot lines (from 2 of the transformer output phase connection) and at the same time the UPS is grounded in the sense of being connected to the Ground/ Neutral

Point 3: Thanks, this has confirmed that the technician's theory is indeed flawed

Point 4: There are other loads connected to the step-down transformer; however I doubt they are causing the power surges. Please refer to the schematic where the entire setup of loads, ELCBs and MCBs are shown

Point 5: The UPS currently only has 1 IEC C20 (16A) input socket; however I will check with the technician again whether any pre-configuration has been tampered before

Point 6: I will also check on the output voltage side

Sorry to everyone for the non-working link; I have uploaded the schematic again. Please copy and paste the link as I don't have enough permission rights to insert URL hyperlink
http://www.flickr.com/photos/44719354@N06/4109903824/
February 14, 2012 6:29:52 AM

IT NOT NORMAL TO EXPERIENCE SHOCK FROM YOUR TV SCREEN AND YOUR PC MULFUNCTIONING BECAUSE OF POWER FRATUATIONS, I WILL SUGGEST FOU INSTALL UNINTERRUPTIBLE POWER SUPPLY UNIT WHICH WILL PROVIDE EMERGENCY POWER TO YOUR MACHINE AND ALSO WHEN THERE IS HIGH VOLTAGE IT WILL HELP TO PREVENT SHOCKS. HOWEVER YOU SHOULD ALSO INSTALL RESIDUAL CURRENT DEVICE TO YOUR ELECTRICAL CIRCUIT .
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