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Anonymous Poster

UPS Output Voltage

06/18/2010 12:21 PM

We are having a problem with the UPS output voltage which will be used for the instrument cabinets. The cabinets require 240 V (Line to Grounded Neutral). The UPS output voltage is 240 V (Line – Line) and the UPS vendor mentioned that none of the line can be grounded. The UPS has voltage system 120 V (Line 1) – 0 (Neutral) – 120 V (Line 2) and the central neutral point is grounded.

Any suggestion to resolve this problem?

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#1

Re: UPS Output Voltage

06/18/2010 1:05 PM

How about one transformer to step it up ?

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#2

Re: UPS Output Voltage

06/18/2010 2:26 PM

Use an isolation transformer (no need to step up). Commonly made to use with variable speed drives. They can be bought with 1:1 ratio, and connect per your line & neutral arrangement.

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#3

Re: UPS Output Voltage

06/18/2010 9:25 PM

If you find 240 between 2 wires of the different outlets use these. Dont use the neutral provided in the UPS. Make one yourself on the massa point. If no 240 available - as posted - extra transformer or new UPS.

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#4
In reply to #3

Re: UPS Output Voltage

06/19/2010 12:22 AM

massa point?

Please elaborate...

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#6
In reply to #4

Re: UPS Output Voltage

06/19/2010 1:08 AM

I will try not to make that mistake anymore: Europe uses Massa- Mass- Masse to specify the metal parts that are eventually touchable and need to be brought to "earth" level. Here known as "ground". In a double isolated (or insulated?- help) fixture that massa is floating - because touching is impossible. (e.g. Bosch electric tools). Where found we use 220- 240 and also live long. It is the same with Gas, Gasoil, Gasoline. The Honda motorcycles in Europe have "only gasoline" stamped on their Gas Cap. Sorry D

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#5

Re: UPS Output Voltage

06/19/2010 12:52 AM

GA peterT,

an isolation transformer is the only safe solution

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#9
In reply to #5

Re: UPS Output Voltage

06/19/2010 6:37 AM

Agree...

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#7

Re: UPS Output Voltage

06/19/2010 1:15 AM

That is possible when the ups has a isolated supply and inverter. Germany makes no difference between Neutral and line in their plugs.

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#14
In reply to #7

Re: UPS Output Voltage

06/19/2010 2:55 PM

That is perfectly true but reads a bit "odd".......

Would you like to expand on that info a little or should I?

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#19
In reply to #14

Re: UPS Output Voltage

06/20/2010 5:33 PM

You are the German, go on. Thanks. D

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#25
In reply to #19

Re: UPS Output Voltage

06/21/2010 8:17 AM

What you wrote is perfectly true, but misleading for some.

The European plugs used in Germany (there are several types, the French version is NOT like this!) are not polarised in any way, so line can come in on either pin to the device, which means that all "ON/OFF" switches MUST be double pole for full safety.

A device sold for the UK market, may only have a single pole switch, designed to remove the line/phase from the device. This could be dangerous if the plug is changed so that it can be used in Germany....

I personally find the German system appallingly dangerous, until I hear about other areas where things are even MORE dangerous.....the best and safest system to my mind remains the UK's ring main system of plugs and sockets......

Each plug being polarised so that it can ONLY be inserted in one way. Also the line/phase is fused in each plug, a fuse suitable for the load needed SHOULD be used, but many Brits only use 13 amp fuses for EVERYTHING, sadly!! This safeguards the house system. Most other systems that I have seen, do not have fused plugs, so a short circuit will usually remove one of the main breakers, taking lighting and power away from an area in a building....

A German (Euro) Schuko plug & socket can be read about here:-

http://en.wikipedia.org/wiki/Schuko

It looks like this:-

and this:-

A UK Mains socket showing the safety shutters can be seen below:-

and a fused plug here:_

The excellent web site for the above is here:-

http://en.wikipedia.org/wiki/BS_1363

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#8

Re: UPS Output Voltage

06/19/2010 2:14 AM

Normally in UPS System, since it is phased in its inversion and conversion, you will get such divided voltage in Phase and neutral. Its better you try grounding the 1st neutral and check the voltage in the output. If you See a UPS diagram only phases are taken by the AC/DC Converter, and pure sine wave is produced in the output.

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#10

Re: UPS Output Voltage

06/19/2010 8:53 AM

If the UPS output is from the secondary of a transformer, which secondary winding is isotated from the primary, then remove the central OV connection to ground. You can then use one of the 120V output as ground and the 2nd output as 240V.

To check, put the UPS OFF from mains (isolate) and remove the ground link from the 0V central pole. Check continuity between any of the output 120V poles and the Inputs of the UPS (Mains connecting cable L & N & Ground wire): there should be no continuity. Then the above should be possible since the output is isolated from the input (electrically).

You should check with the vendor or someone maintaining these equipment before executing this change. (If the grounding of the cabinet instrumentations is really required...) Propose this change and see if acceptable by the vendor in case of warranty validation.

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#11

Re: UPS Output Voltage

06/19/2010 11:06 AM

Insulation transformer is the best solution.

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#13
In reply to #11

Re: UPS Output Voltage

06/19/2010 12:56 PM

ISOLATION = Isolate, Separate

INSULATION = Insulate, protect, put in an island

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#12

Re: UPS Output Voltage

06/19/2010 11:38 AM

Are you absolutely sure your equipment requires a neutral to line voltage of 240? What kind of equipment is this. It seems a bit strange to have such an unusual requirement.

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#15
In reply to #12

Re: UPS Output Voltage

06/19/2010 3:05 PM

I believe all of europe and many other countries (Russia, China, India, Pakisrtan, Malaya, Singapore, Australia and New Zealand - to name but a few....) use this standard......220 - 240 VAC 50 HZ.

You might say that probably 240 VAC 50 HZ is used in more countries by more people than 110-120VAC.... therefore 240VAC is really the world "Norm".

110-120VAC is mostly N.America /Canada/and about half of S.America.....

Look here:-

http://en.wikipedia.org/wiki/Mains_power_around_the_world

You might get a shock!! (Pun intended!)

So why is this thought to be unusual?

Are you on that "unusual" 110 - 120 VAC 60HZ system?

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#17
In reply to #15

Re: UPS Output Voltage

06/20/2010 2:44 PM

No, no, you misunderstood me. I'm fully aware of the 240V 50Hz world but what I didn't know was that one leg is at neutral (or ground potential) and the other at 240. I thought you had 240 between each leg of the feed but not one at 240 and the other at zero. Excuse me for any confusion. We all use 240 over here but from L1 to L2 and 120 from L1 or L2 to ground or neutral.

Sorry. I've installed and currently maintain dozens of medium to large UPS's so thats where the question came from.

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#18
In reply to #17

Re: UPS Output Voltage

06/20/2010 4:20 PM

I may make a slightly too sweeping statement, but it should be correct for 99% of the world I think:-

Nominal 230 VAC (are usually) 50HZ systems have usually 3 wire, earth, neutral and line or phase.

In 115 V countries, you get also a possibility for two phases, which gives around 220 volts as well, but line to line, with a central neutral and an earth.....usually at 60HZ...

The safety methods vary slightly, but a good point is that with the US system, a short to earth (via a human for example) is only around 115Volts and not 230!!! Still bad enough!!

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#21
In reply to #18

Re: UPS Output Voltage

06/20/2010 8:37 PM

I have been careless enough to have been shocked quite a few times by 120V60Hz here in the US, and a few times by 240V50Hz abroad. I was surprised to find that the sensation felt was MUCH more dependent on the conditions, than on the voltage. I was once knocked across a small room by 120V in damp conditions, while all the times I got shocked by 240V were in dry conditions, and there was no obvious increase in pain from those 240V shocks over those from 120V shocks in dry conditions.

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#16

Re: UPS Output Voltage

06/20/2010 12:32 PM

A 1:1 isolating transformer is Ur best bet as it provide the needed safety isolation and a grounding option. It can be a 110volt center tap or a 220 volt isolation transformer.PeterT is wright.

Dickson.

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#20

Re: UPS Output Voltage

06/20/2010 5:42 PM

Hi Guys, Isolation transformers can make you die too. No more, no less than with your UPS isolated. Want to buy a transformer? Go for it. I feel confident without. If your day and destination is set for electrocution by that UPS, you will die 4 microseconds earlier from 240 than from 120.

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#22
In reply to #20

Re: UPS Output Voltage

06/20/2010 11:50 PM

Isolation transformer suggested here is not to prevent electrocution,

all this debate in not responding to the original post....

the poster has a cabinet, whatever it is, supplied by 240V single phase, one wire of this supply input is wired to ground.

His ups is 240 V with center tap, (120-0-120) the center tap is grounded , result, none of the 120V lines could be grounded so he can not use the 240 V, because one line will be shorted to the center tap by the ground wire of the cabinet

the solution is, per my humble opinion, an isolation transformer; or to remove the ground wire from the cabinet or the UPS, as LAA_Lucke suggested in post # 10, which is less safe

Regards to all

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#26
In reply to #22

Re: UPS Output Voltage

06/21/2010 8:19 AM

GA from me and I agree completely with your comments.

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#28
In reply to #26

Re: UPS Output Voltage

06/21/2010 9:45 AM

THANKS !!!! I always wait for your comments

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#30
In reply to #28

Re: UPS Output Voltage

06/21/2010 10:07 AM

You wrote:-

I always wait for your comments

Is that good or bad? Now I am completely unsure......

Have a great day in spite of me!!

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#31
In reply to #30

Re: UPS Output Voltage

06/21/2010 10:50 AM

Andy,

I am saying good about your comments, I like your posts and in any thread I search for your replies. Why it should be bad?

Have a great day in spite of YOU!!

Greetings

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#32
In reply to #31

Re: UPS Output Voltage

06/21/2010 12:00 PM

Cheers Buddy!

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#27
In reply to #22

Re: UPS Output Voltage

06/21/2010 8:29 AM

Le Noble,

My suggestion was: to check the UPS output. It usually has a transformer with a secondary isolated from the primary. If this is the case, the central tapping to the ground can be removed and one end of the 120V can be put to ground, therefore providing a return for whatever is protecting the cabinet wiring. This will be as safe as the central tapping on the 0V. The neutral / Ground is only a relative concept to return the flow.

Safety: The above must be checked. Guarantee from supplier dictates that any modification should be agreed otherwise voids the guaratee on the equipment for what ever fault might develop, not necessarily due to this modification.

I hope this was clear from me.

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#29
In reply to #27

Re: UPS Output Voltage

06/21/2010 10:00 AM

LUCKE

I refered to your comments as a good alternative to transformer solution, what I meant by (not safe) is excactly what you explained in this post about guarantee, and also, doing modification by not-qualified person may lead to do unwanted modifications, excuse my english not to elaborate my idea correctly...

I noticed the complete absence of the poster from this debate, I hope he find the good solution .

Greetings

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#35
In reply to #29

Re: UPS Output Voltage

06/21/2010 3:02 PM

Cheers.

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#23

Re: UPS Output Voltage

06/21/2010 4:40 AM

Can you check in the circuit diagram of the UPS whether there is a centre tap single phase transformer between the inverter circuit and the load terminals?

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#24

Re: UPS Output Voltage

06/21/2010 7:12 AM

As already described, you should remove the ground from center tap internally in the UPS or use an isolation tranformer.

So, you can use 240V line to line with one of them line ground without problems.

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#33

Re: UPS Output Voltage

06/21/2010 12:44 PM

Removing the center ground point on the secondary side of the transformer may give the required output voltage with one leg grounded, but it would change all of the output receptacles on the back of the UPS to 240vac wich could be a safety issue for someone unaware of the internal change. I think it would be wiser to use an isolation transformer dedicated to that specific load that requires 240vac. This would leave the receptacles on the back of the original UPS available for other 120vac uses if required.

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#34
In reply to #33

Re: UPS Output Voltage

06/21/2010 12:58 PM

I agree with Elroy

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#36

Re: UPS Output Voltage

06/21/2010 4:26 PM

I think you will need either an expensive isolation transformer with a center tap or buy from a vendor who has a center-tap output transformer in the UPS. ( We can help)

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#37
In reply to #36

Re: UPS Output Voltage

06/21/2010 7:15 PM

Thanks everybody for the valuable comments and suggestions. I am so grateful to you all.

From all the above discussions, I understood there are two solutions:

  1. Use an isolation 1:1 ratio transformer and ground one of the terminal of the secondary side of the isolation transformer and consider it as neutral.
  2. Remove the grounding from the center 0 point and ground one of the line to make it neutral.

We will discuss both of the options and discuss with the UPS vendor and see which one is good for this particular case.

(Just to reply to one of the participants: The instrument panel requires neutral terminal to comply with the standard for using the filter. With live voltage terminals, the panel vendor indicated that the filter may not work properly).

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#38
In reply to #37

Re: UPS Output Voltage

06/21/2010 7:39 PM

Thanks for getting back to us with your summary! Please let us know you final results...

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#39
In reply to #37

Re: UPS Output Voltage

06/22/2010 11:13 AM

You might be interested that we can provide an inverter with split phase output (no isolation transformer needed):

Also a similar model is available if there are 240 loads. The above is to supply power to a split phase panel with 120 v loads only.

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#40
In reply to #39

Re: UPS Output Voltage

06/23/2010 10:28 AM

Any one can inform me about the difference between "AC HOT 1 IN" and "AC HOT 2" IN in the schematic attached.

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#41
In reply to #40

Re: UPS Output Voltage

06/23/2010 11:19 AM

You cannot attach schematics in the way you tried.....

You need to send them via normal email to people who send you their normal email address.

You can post pictures, but pictures of schematics can seldom be read here.

I would send you my email address, but you are logged on as a guest........so its not possible!!

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#42
In reply to #41

Re: UPS Output Voltage

06/23/2010 1:41 PM

The schematic is very clear by post#39.

I can read it with no problem.

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#44
In reply to #42

Re: UPS Output Voltage

06/24/2010 6:59 AM

Not all are so simple.....but you are right, a very simple schematic can be read OK....

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#43
In reply to #40

Re: UPS Output Voltage

06/23/2010 4:41 PM

Since J.Lyons has not responded, I'll try:

As Andy indicated, I hardly consider the image of post #39 as 'clear', but it is (barely) readable.

I don't know why he indicated 'split phase' 120V. To me, 'split phase' refers to the standard Household wiring in the USA, where a 240V transformer (supply to the house) has a grounded center tap. Thus there is available 120V between either 'Hot' line and ground, and there is 240V between the 2 'Hots'. The two 'Hot' lines can never be connected to each other.

Notice that at the output of the Inverter, it specifies zero Volts between 'AC HOT 1 OUT' and 'AC HOT 2 OUT', and if you follow the circuit through the 'AC HOT Transfer Relay', you will see that the same transformer winding supplies both 'AC HOT 1 OUT' and 'AC HOT 2 OUT'. So this is NOT a split phase output; it is two single phase outputs having the same phase, or more accurately, a single output with two connections.

Thus 'AC HOT 1 IN' and 'AC HOT 2 IN' MUST both be 120V of the same phase. I see no reason for the two inputs, except that when the inverter is not acting as a 120V supply, 'AC HOT 1 IN' remains connected to the inverter transformer, so it could presumably act as a part of a battery charger (not detailed in this diagram), whereas 'AC HOT 2 IN' is totally separated from the inverter. I'd call this a 'Block Diagram', not a 'Circuit Diagram'.

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#46
In reply to #40

Re: UPS Output Voltage

06/25/2010 9:57 AM

This arrangment makes it easy to power up what is normally a 240 vac panel with a 120 vac inverter. you do without the 240 loads during the outage.

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#47
In reply to #46

Re: UPS Output Voltage

06/25/2010 10:09 AM

I think this arrangement outputs 120vac only not 240vac.

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#48
In reply to #46

Re: UPS Output Voltage

06/25/2010 10:59 AM

OK, now I think I understand.

The diagram IS labeled 'Inverter Mode'. In inverter mode, it applies 120V of the same phase to both hot lines (NOT split phase), so 120V devices on both of those lines will work, but there is no voltage difference between the two hot lines, so 240V devices will see no power.

In "Power Line Mode", the split phase 240V (2-120V sources of opposite phase) is carried through the relay, so everything works.

There must be a short time,while the relay is switching, that the AC OUT 2 has no power and then suddenly reverses phase (or comes back on with the opposite phase). I would not want sensitive equipment powered from AC OUT 2.

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#49
In reply to #48

Re: UPS Output Voltage

06/25/2010 11:32 AM

Thanks dkwaner for your explanation, so we can say that that the the control panel is connected between "AC HOT 1 OUT" and "AC NEUTRAL OUT" which in 120vac all the time ?

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#50
In reply to #49

Re: UPS Output Voltage

06/25/2010 12:15 PM

Not Quite. There will also be a short delay between when the normal power goes out, the UPS detects and responds to the outage, and switches the 'Hot Transfer Relay' on 'AC HOT 1 OUT'.

I don't know if you are the OP, but the bottom line is that this device will NOT work for the OP's project, because that is 240V.

J.Lyons says there is also a 240V unit - we need to see it's diagram to see whether it is appropriate.

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#45
In reply to #39

Re: UPS Output Voltage

06/25/2010 8:54 AM

Hello Lyons

We are UPS manufacturer in India , regarding to DC/AC inverter section of Figure 3-1 you provided, is it "full bridge" inverter ?

Thanks for help

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#51
In reply to #45

Re: UPS Output Voltage

06/25/2010 7:56 PM

This type of DC/AC inverter should be true sine wave inverter.

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Anonymous Poster
#52

Re: UPS Output Voltage

06/25/2010 10:19 PM

Hello Lyons

Could you please inform me :

What is the maximum KVA which can be obtained from such DC/AC FET inverter ?

Thanks for help in advance.

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#53
In reply to #52

Re: UPS Output Voltage

08/16/2010 8:54 AM

sorry to have been out of touch...............

I think the answers are 'full bridge': yes;

and i don't know the max KVA possible. I see new products available at 6000, and 8000 watts. I think economics is the limitation. After all there's a lot of high quality Iron and copper involved............and in order to make use of that high watt capability you need a lot of lead or whatever your battery choice is. at some point you will be comparing energy storage in batteries vs fuel and the pros and cons of each

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Anonymous Poster
#54

Re: UPS Output Voltage

02/13/2011 6:24 PM

Hello,

i request for UPS 3KVA -5KVA.

pls ,kind send your quote and the specifications, if possible advise on functions

thanks

christian

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#55
In reply to #54

Re: UPS Output Voltage

02/23/2011 10:02 AM
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