universal uninterruptible power supply

A fixed frequency design for either 50 or 60 Hz would be pretty standard. I haven't seen many (any?) UPS with a frequency switch or auto frequency setting - they all tend to be for a single fixed frequency.

My first thought would be for either a ferro-resonant or a double conversion "online" type - without any bypass mode.

Of course it could be done without transformers in a number of ways - an mg set springs to mind. And the transformers themselves, if used, need not be at mains frequency. But why would you want to avoid transformers?

-- Sue

** The above question simply does not make any sense.

Reversal of the active and neutral conductors is of no consequence in the vast majority of AC powered devices.

The range of AC input voltage and frequency you mention is within the capability of most UPS on the market.

Now, what is you actual question ??

..... Phil

On Sat, 07 Feb 2009 01:27:44 GMT Palindrome wrote: | snipped-for-privacy@ipal.net wrote: |> What would it take in the design of a UPS to make it work correctly and safely |> under conditions where the incoming power could have either wire grounded or |> neither wire grounded (but there will always be a separate equipment grounding |> conductor), and will operate over the nominal voltage range of 200 to 240 with |> either 50 or 60 Hz input? | | A fixed frequency design for either 50 or 60 Hz would be pretty | standard. I haven't seen many (any?) UPS with a frequency switch or auto | frequency setting - they all tend to be for a single fixed frequency.

A great many I have seen do have 50/60 Hz frequency agility. There are countries with 220-240 volt (L-N) systems at 60 Hz. Brazil is one of them (for the portion of the country running on 60 Hz).

However, I would consider it more interesting to see how the engineers deal with the grounding aspect.

|> A big question might be what kind of output power it would have, such as if |> either wire can be grounded, a specific wire would be grounded, or neither |> wire would be grounded. Would the output always be a specific design, or |> could it follow what the input is. Would it be able to safely have a bypass |> mode, or would that have to be omitted? | | My first thought would be for either a ferro-resonant or a double | conversion "online" type - without any bypass mode.

So just eliminate the bypass mode, and provide some kind of switch to select whether the ground is connected between the two 100-120 volt output inverters (for a system like in the USA) or on one end (for a system like in UK).

I'll assume "double conversion online" type.

| Of course it could be done without transformers in a number of ways - an | mg set springs to mind. And the transformers themselves, if used, need | not be at mains frequency. But why would you want to avoid transformers?

Why spend the extra cost and suffer the electrical waste if it's possible to do without them (either the transformer or the motor-generator set)?

I would envision a UPS with 2 inverters in the 100-120 agile voltage range which could be connected in series, with the ground switchable between the middle between them, or on one end. With a bit more in the switching, the

2 inverters could even be wired in parallel to get 100-120 volts out instead of 200-240. No transformer needed. No mg set needed.

How complex would that switching have to be? What would be involved in making it safe enough to get it listed by various listing entities (UL, TUV, etc). Would latching relays be good enough?

On Sat, 7 Feb 2009 14:22:31 +1100 Phil Allison wrote: | | | |> What would it take in the design of a UPS to make it work correctly and |> safely |> under conditions where the incoming power could have either wire grounded |> or |> neither wire grounded (but there will always be a separate equipment |> grounding |> conductor), and will operate over the nominal voltage range of 200 to 240 |> with |> either 50 or 60 Hz input? | | | ** The above question simply does not make any sense. | | Reversal of the active and neutral conductors is of no consequence in the | vast majority of AC powered devices.

What about "grounded center", where 2 inverters working in sync in the range of 100-120 volts are wired in series, and the grounding connection can be switched between the center and one end?

| The range of AC input voltage and frequency you mention is within the | capability of most UPS on the market.

But what about the ability to safely operate in all electrical systems in the world (at the 200-240 volt configuration in countries like USA and Japan that operate on 100-120 volts L-N with 2 opposiing phase lines which may be

180 degrees apart, or may be 120 degrees apart).

| Now, what is you actual question ??

Same as before: "What would it take ...". I'll refine and specify that the cost, engineering complexity, and safety, would be the focus of that question (which is generally what engineering addresses).

| ** A centre grounded ( ie split 120v -0- 120v ) supply poses no problems either.

Sometimes called a "balanced supply" and sold openly to the public.

You are completely clueless.

** Totally NEW question.

(at the 200-240 volt configuration in countries like USA and Japan

** A centre grounded ( ie split 120v -0- 120v ) supply poses no problems either.

You are completely clueless.

** Then yours is STILL an utterly silly question.

For Christ's sake - TELL US what YOU think the safety problem is ??

...... Phil

Thanks for that - only goes to show, I have never seen one with frequency agility, the ones I have seen have either been 50 or 60 Hz. Of course it would be easy enough to sample the incoming supply, on connection, store that value and use it to set the inverter output frequency. Plus, for a stepped output unit (not a "true" sine wave output unit) the frequency change within the inverter wouldn't have a great design implication.

A transformer operating at a frequency rather higher than mains is pretty cheap, small and efficient and, IME, very reliable..

But I would suggest a lot more expensive and larger and less reliable than one inverter plus 20+KHz transformer.

The switching itself would be pretty trivial - a little more complex would be the sensing to ensure fail-safe. Hence mostly down to relay design - eg extra contact sets that prevent the inverter(s) operating (or operating at significant power levels) if the required safe operating conditions hadn't been achieved during the initial phase of transfer.

-- Sue

With a transformer isolating the input side from the output side, all questions of grounding this side or that side, become non-issues. Transformer isolation can allow the output circuitry to be designed completely floating, allowing you to ground or not ground either leg without regard to incoming.

Running two inverters in series or parallel is almost *always* harder to do than running a single, larger one. Getting the triggering and output stages to 'play nice' and always work together reliably is harder then just getting larger power stage components.

daestrom

How in hell can "2 opposing phase lines"..."be 120 degrees apart"?

| A transformer operating at a frequency rather higher than mains is | pretty cheap, small and efficient and, IME, very reliable..

Of course a higher frequency means a smaller transformer. But then, you don't have 50/60 Hz output from that transformer.

|> I would envision a UPS with 2 inverters in the 100-120 agile voltage range |> which could be connected in series, with the ground switchable between the |> middle between them, or on one end. With a bit more in the switching, the |> 2 inverters could even be wired in parallel to get 100-120 volts out instead |> of 200-240. No transformer needed. No mg set needed. | | But I would suggest a lot more expensive and larger and less reliable | than one inverter plus 20+KHz transformer.

And I would suggest 20 kHz would have issues providing power for other devices, including computer PSUs.

If output needs to be 50 and/or 60 Hz, and sine wave, now what?

On Sat, 7 Feb 2009 08:08:28 -0500 daestrom wrote: | snipped-for-privacy@ipal.net wrote: |> On Sat, 07 Feb 2009 01:27:44 GMT Palindrome wrote: | |>> Of course it could be done without transformers in a number of ways |>> - an |>> mg set springs to mind. And the transformers themselves, if used, |>> need |>> not be at mains frequency. But why would you want to avoid |>> transformers? |>

|> Why spend the extra cost and suffer the electrical waste if it's |> possible |> to do without them (either the transformer or the motor-generator |> set)? |>

| | With a transformer isolating the input side from the output side, all | questions of grounding this side or that side, become non-issues. | Transformer isolation can allow the output circuitry to be designed | completely floating, allowing you to ground or not ground either leg without | regard to incoming.

True. But at 50/60 Hz, this is a big transformer. And I do not see a need to produce a system type different than what is coming in. If the derived system is made to match the supply system, then engaging the bypass would not change the nature of the system.

|> I would envision a UPS with 2 inverters in the 100-120 agile voltage |> range which could be connected in series, with the ground switchable |> between the middle between them, or on one end. With a bit more in |> the switching, the 2 inverters could even be wired in parallel to get |> 100-120 volts out instead of 200-240. No transformer needed. No mg |> set needed. |>

| | Running two inverters in series or parallel is almost *always* harder to do | than running a single, larger one. Getting the triggering and output stages | to 'play nice' and always work together reliably is harder then just getting | larger power stage components.

So how can you produce a "grounded center tap" system with a "single, larger" inverter?

If the derived system is _not_ a "grounded center tap" type system, then that would complicate the bypass switching, because that would mean a sudden shift in grounding relations when the bypass is engaged.

On Sat, 7 Feb 2009 17:29:57 +1100 Phil Allison wrote: | | | |> |> What would it take in the design of a UPS to make it work correctly and |> |> safely |> |> under conditions where the incoming power could have either wire |> grounded |> |> or |> |> neither wire grounded (but there will always be a separate equipment |> |> grounding |> |> conductor), and will operate over the nominal voltage range of 200 to |> 240 |> |> with |> |> either 50 or 60 Hz input? |> | |> | |> | ** The above question simply does not make any sense. |> | |> | Reversal of the active and neutral conductors is of no consequence in |> the |> | vast majority of AC powered devices. |>

|> What about "grounded center", where 2 inverters working in sync in the |> range of 100-120 volts are wired in series, | | | ** A centre grounded ( ie split 120v -0- 120v ) supply poses no problems | either. | | Sometimes called a "balanced supply" and sold openly to the public. | | You are completely clueless.

Before I put a the label on you that many other people already have, I will ask you to be specific. Let's see if you really understand this and can actually read what has been posted ... by stating exactly what you think I an clueless about. If you can't state this correctly, then what you are doing is just making personal attacks (which most people will interpret as someone who can't defend what they say in a technical way).

|> | The range of AC input voltage and frequency you mention is within the |> | capability of most UPS on the market. |>

|> But what about the ability to safely operate in all electrical systems in |> the world | | ** Totally NEW question.

How is this a new question? You can't see the relation, and thus a basic expansion of, the original question?

| (at the 200-240 volt configuration in countries like USA and Japan |> that operate on 100-120 volts L-N with 2 opposiing phase lines which may |> be |> 180 degrees apart, or may be 120 degrees apart). | | | ** A centre grounded ( ie split 120v -0- 120v ) supply poses no problems | either. | | You are completely clueless.

Before I put a the label on you that many other people already have, I will ask you to be specific. Let's see if you really understand this and can actually read what has been posted ... by stating exactly what you think I an clueless about. If you can't state this correctly, then what you are doing is just making personal attacks (which most people will interpret as someone who can't defend what they say in a technical way).

|> | Now, what is you actual question ?? |>

|> Same as before: "What would it take ...". | | | ** Then yours is STILL an utterly silly question. | | For Christ's sake - TELL US what YOU think the safety problem is ??

The safety problems would depend on the specific design. If relays that can, under conditions of failure (e.g. one of them might not make the switch for reasons that might include an open coil) result in an unsafe condition (such as exposing operators to dangerous voltage, or create a fault condition), then it could be (should be) considered unsafe by listing agencies. That can be mitigated by making the design use "double throw" relays that just cannot be in both states at once (though could be in an in between state).

One design idea was to have 2 inverter sections in series, with each of the

3 connections having a relay that could connect that section to ground. But this exposes at least two risks. One is relay operation failure could leave the system ungrounded. Or if latching relays are involved, two could be closed at once (due to an open operation failure) and a fault is created. One way to mitigate that problem is for the control logic to always complete the switching, AND test the continuity state, before activating inverter operations. If supply power is lost, it could come back with different grounding (for example, with Schuko, the plug can be inverted). Now for the grounding of the derived system to be corrected to match, power output has to be briefly shut off (even if for maybe only a cycle or two).

I've thought through quite a number of different design arrangements. Each one has some issue somewhere. Many are issues that safety listing agencies might have big concerns about.

On Sat, 07 Feb 2009 18:50:29 -0600 krw wrote: | On 7 Feb 2009 05:40:18 GMT, snipped-for-privacy@ipal.net wrote: | |>On Sat, 7 Feb 2009 14:22:31 +1100 Phil Allison wrote: |>| |>| |>| |>|> What would it take in the design of a UPS to make it work correctly and |>|> safely |>|> under conditions where the incoming power could have either wire grounded |>|> or |>|> neither wire grounded (but there will always be a separate equipment |>|> grounding |>|> conductor), and will operate over the nominal voltage range of 200 to 240 |>|> with |>|> either 50 or 60 Hz input? |>| |>| |>| ** The above question simply does not make any sense. |>| |>| Reversal of the active and neutral conductors is of no consequence in the |>| vast majority of AC powered devices. |>

|>What about "grounded center", where 2 inverters working in sync in the |>range of 100-120 volts are wired in series, and the grounding connection |>can be switched between the center and one end? |>

|>

|>| The range of AC input voltage and frequency you mention is within the |>| capability of most UPS on the market. |>

|>But what about the ability to safely operate in all electrical systems in |>the world (at the 200-240 volt configuration in countries like USA and Japan |>that operate on 100-120 volts L-N with 2 opposiing phase lines which may be |>180 degrees apart, or may be 120 degrees apart). | | How in hell can "2 opposing phase lines"..."be 120 degrees apart"?

Source supply is 2 phases taken from a 3 phase system, such as 208Y/120 as found in USA and Canada, or 220Y/127 as found in Mexico. In Mexico, it is more common to have 120 degree phasing than to have 180 degree phasing.

** Yawnnnnnnn - more absurd gobbledegook............. ** You clearly have no clue of the difference between supply neutral and safety ground.

Go away - IMBECILE.

...... Phil

On Wed, 11 Feb 2009 14:41:12 +1100 Phil Allison wrote: | | | |> | ** Then yours is STILL an utterly silly question. |> | |> | For Christ's sake - TELL US what YOU think the safety problem is |> ?? |>

|>

|> The safety problems would depend on the specific design. If relays that |> can, |> under conditions of failure (e.g. one of them might not make the switch |> for |> reasons that might include an open coil) result in an unsafe condition |> (such |> as exposing operators to dangerous voltage, or create a fault condition), |> then |> it could be (should be) considered unsafe by listing agencies. That can |> be |> mitigated by making the design use "double throw" relays that just cannot |> be |> in both states at once (though could be in an in between state). | | | ** Yawnnnnnnn - more absurd gobbledegook.............

So, basically, you really were doing nothing but making personal attacks.

|> One design idea was to have 2 inverter sections in series, with each of |> the |> 3 connections having a relay that could connect that section to ground. | | | ** You clearly have no clue of the difference between supply neutral and | safety ground.

I sure do. But do you? Given your failure to explain yourself, it is now clear that you do not believe your own knowledge to be defensible.

| Go away - IMBECILE.

Not a chance.

** Yaaaaawnnnnnnn - more ABSURD gobbledegook...... ** You clearly have no clue of the difference between supply neutral and safety ground.

Go away - IMBECILE.

** No you do not.

Cos you keep referring to neutral as "ground".

AC supply conductors are NOT and CANNOT be linked to "ground" inside any appliance.

FUCKWIT !!

..... Phil

For a 20kHz transformer, its output is going to be converted to (typically several hundred volts) DC and then fed to an output stage that generates the 50/60Hz required.

Design the output stage to match the requirement. A true sine wave

50/60Hz oscillator linked to a power amplifier supplied from the DC obtained from the 20kHz transformer will do nicely, if sine wave output is required. Although, often, stepped "sine wave" output is going to be cheaper, more efficient and acceptable.

-- Sue

The "2 opposing phase line" still have a 180 degree relationship to each other, moron. Two lines *CANNOT* be 120 degrees from each other.

I never said the transformer had to be 50/60. Take the line, rectify it, then invert it at high frequency and drive the primary of a *small* transformer. Take the secondary, rectify it and drive a power inverter at

50/60. Complete isolation and no 'big transformer'.

Ah, for that you *would* use a large 50/60 transformer as the output stage. Drive at 240 and have center-tapped secondary. At least that's one way. There may be others.

So that would be a compromise of either a big bulky 50/60 transformer or more-difficult/ less-reliable inverter design.

If the service is for a grounded center tap, then simply ground the center of the inverter output (either center-tap of power 50/60 transformer or leg between your two-inverter design). With *just* a ground connection on the secondary side, there isn't any interaction with the mains.

Obviously if the unit is to be used in a variety of service, the exact grounding of the output has to be user configurable. But if the output is isolated from input using either a high-frequency or low-frequency transformer, you can ground any *one* point of the output with no ill-effects.

(well, grounding one side of a power inverter so it 'looks' like a grounded-on-one-side UK supply, *may* cause some noise issues and EMI that affects other equipment, but the basic inverter would still be operational).

daestrom

On Wed, 11 Feb 2009 09:43:58 GMT Palindrome wrote: | snipped-for-privacy@ipal.net wrote: |> On Sat, 07 Feb 2009 08:50:26 GMT Palindrome wrote: |> |> | A transformer operating at a frequency rather higher than mains is |> | pretty cheap, small and efficient and, IME, very reliable.. |> |> Of course a higher frequency means a smaller transformer. But then, you |> don't have 50/60 Hz output from that transformer. | | For a 20kHz transformer, its output is going to be converted to | (typically several hundred volts) DC and then fed to an output stage | that generates the 50/60Hz required.

So how many total stages are involved with all this, and how much power loss is involved as a result? You have to convert the power to 20 kHz first just to use that lightweight transformer. Then you have to convert it back to ultimately 50/60 Hz again. It would seem to me that all that conversion would make the reduced transformer loss meaningless.

|> |> I would envision a UPS with 2 inverters in the 100-120 agile voltage range |> |> which could be connected in series, with the ground switchable between the |> |> middle between them, or on one end. With a bit more in the switching, the |> |> 2 inverters could even be wired in parallel to get 100-120 volts out instead |> |> of 200-240. No transformer needed. No mg set needed. |> | |> | But I would suggest a lot more expensive and larger and less reliable |> | than one inverter plus 20+KHz transformer. |> |> And I would suggest 20 kHz would have issues providing power for other |> devices, including computer PSUs. |> |> If output needs to be 50 and/or 60 Hz, and sine wave, now what? |> | | Design the output stage to match the requirement. A true sine wave | 50/60Hz oscillator linked to a power amplifier supplied from the DC | obtained from the 20kHz transformer will do nicely, if sine wave output | is required. Although, often, stepped "sine wave" output is going to be | cheaper, more efficient and acceptable.

Stepped sine wave may well work fine, if there are enough steps involved. But supply power is 220 to 240 V (200 V in Japan), at 50 or 60 Hz, and the output needs to be the same.