Coping With Low Voltage Mains

[zzSleepyJohn]

There's an old fashioned type of voltage regulator that I believe is still available in some electrical shops that consists of nothing but a step-up transformer that's overwound so it's core is always in saturation. It doesn't matter what the input voltage is, the output is always flattened off by the core saturation and so remains virtually the same. The only snag is that the output, being squared off by the saturation is far from sinusoidal, and is rich in harmonics.

Around 12 years ago, before the days when domestic TVs had built-in regulating power supplies, I believe this type of transformer was quite popular to correct for the small size and rolling pictures that were prevalent during mains brownouts in those days.

My question is whether anyone has experience of using this cheap very basic type of voltage regulator to power a desktop computer. Can such a device be an answer to frequent yet lengthy brownouts that cause a UPS to go on to battery and the battery to run out?

I've seen references to voltage regulators and to automatic voltage regulators (AVRs) in other threads in this forum. For example

http://www.thaivisa.com/forum/index.php?sh...ltage+regulator post #8 and

http://www.thaivisa.com/forum/index.php?sh...lator&st=10 post #12.

but I'm not altogether clear on the nomenclature being used and exactly what's meant by a "voltage regulator" and by an "AVR" in these threads, although I can see the picture in the 2nd reference shows a much more sophisticated and expensive device to the simple saturated core transformer I'm talking about.

Any info on using a voltage regulator to compensate for brown outs would be much appreciated.

+ SJ

[Crossy]

Get a decent AVR (Automatic Voltage Regulator) the saturation type are suceptible to frequency variations, there are much better modern solutions. The clever AVRs either consist of a motor driven variac to maintain the output, or a descrete tap-switching transformer both controlled by some simple electronics.

Feed your UPS with it. An AVR will ensure that your UPS batteries remain fully charged during lengthly periods of reduced voltage.

Edited January 8, 2008 by Crossy

[Thanh-BKK]

Hi

I got a rather simple UPS (Leonics 750 VA) which copes very well with brown-outs - as they happen sometimes here, i measure 100-ish Volts on the mains then with a digital multimeter. My room light stays on thanks to a "Lamptan" electronic ballast and even the TV stays on and running normal (multi-voltage capable), however the UBC goes out and fan and fridge too.

In such case the UPS clicks a few times, but doesn't even start beeping as it does when the power goes completely - it just keeps going. I guess it just draws more amps from the 100 Volts than it would from 220 to yield the same output..... nowhere it mentions that this particular UPS is meant for multi-voltage use (like on the TV which got a sticker "110-250 Volts").

What is actually the reason for such brown-outs on single-phase systems? When "it" happens it usually lasts for up to an hour at my place (Bangna), normally followed by a short complete outage and then return of the full voltage.

Best regards....

Thanh

[zzSleepyJohn]

*SNIP*

What is actually the reason for such brown-outs on single-phase systems? .....

Almost certainly it's simple I x R drop due to overload in the local distribution cables. It gets worse in the evenings when lights are swiched on around the neighbourhood , and using the shower heater usually causes the UPS to go over on to battery.

Unaccountably, though, there are odd days when everything is fine with no brownouts at all.

+ SJ

[paulfr]

Since the voltage needed to run a PC is around 15 volts and the input mains delivers 110 vrms, it is much easier to design the electronic voltage regulator following the power supply [transformer, diodes and filter cap] to handle full load at a lower voltage than the usual 110 plus or minus 10 percent.

You [the designer] just need to have the secondary put out more voltage so the regulator will work even when the mains is very low, say at 80vrms. But the tradeoff is that the regulator will be dissipating much more power during normal voltage operation and this costs money.

As for saturation, the harmonics could fly through the parasitics and take out a semiconductor device. And I doubt that the xformer could deliver full load thru a saturated core.

Cheers

Edited January 9, 2008 by paulfr

[Crossy]

Since the voltage needed to run a PC is around 15 volts and the input mains delivers 110 vrms, it is mu......

...... dissipating much more power during normal voltage operation and this costs money.

As for saturation, the harmonics could fly through the parasitics and take out a semiconductor device. And I doubt that the xformer could deliver full load thru a saturated core.

I don't want this thread to degenerate into the usual is/isn't argument that so often occurs BUT:-

The mains voltage in Thailand is 220V RMS (quite important for our US cousins)

Computers don't use linear PSUs as described by paulfr they are far to inefficient at the voltages and currents used by modern computers, see here http://en.wikipedia.org/wiki/Switched-mode_power_supply

Paulfr is quite correct about the saturation type (actually they are ferro-resonant devices) voltage regulators generating transients/harmonics and other nasties, although they use some very clever core materials, capacitors and air gaps to reduce the problem and improve the regulation. They are certainly the cheapest form but are however larger/heavier than the variac, tap switching or magnetic induction (brushless) types which are the 'modern' solution

Edited January 9, 2008 by Crossy

[zzSleepyJohn]

..... I doubt that the xformer could deliver full load thru a saturated core.....

Clearly it couldn't, but isn't that just a question of the designer determining what actual load it can handle, and applying an appropriate rating label on the box? It's understood that using a saturating core method of regulation will necessarily waste some power as heat in the core.

As for saturation, the harmonics could fly through the parasitics and take out a semiconductor device.

Yes, agreed, this might be a show-stopper, but on the other hand don't popular cheap-and-cheerful UPSs output something close to a square wave when they're on battery? UPSs don't normally take a computer's semiconductors out, so why would a saturating voltage regulating transformer be any worse than a UPS in this respect?

+ SJ

[Thanh-BKK]

but on the other hand don't popular cheap-and-cheerful UPSs output something close to a square wave when they're on battery? UPSs don't normally take a computer's semiconductors out, so why would a saturating voltage regulating transformer be any worse than a UPS in this respect?

+ SJ

Hi

Fully agreed - because when i have a power outage, my computer keeps going just fine on the UPS. BUT if i connect a very simple device to it - an electric fan, no more - this unit will run too but it sounds like..... don't know, like falling apart any moment. So the AC coming from the UPS is almost unusable for a simple electric motor, yet such a sensitive thing as a computer does well with it. And the fan in question has a max. power of 30 watts, far less than the computer, so THAT is no issue

Best regards.....

Thanh

[zzSleepyJohn]

Fully agreed - because when i have a power outage, my computer keeps going just fine on the UPS. BUT if i connect a very simple device to it - an electric fan, no more - this unit will run too but it sounds like..... don't know, like falling apart any moment. So the AC coming from the UPS is almost unusable for a simple electric motor, yet such a sensitive thing as a computer does well with it. And the fan in question has a max. power of 30 watts, far less than the computer, so THAT is no issue

Best regards.....

Thanh

Thanks, yes, that's an interesting comment about the fan. Probably because the fan is a largely inductive load so the high freq harmonics are hitting up against it's highly inductive impedance.

But actually the most critical device we need to run during brown-outs is an ADSL modem. Would ideally like to run the desktop as well (which is where the voltage regulator would come in), but without the desktop's load, a UPS on battery can keep just a modem on is own going for a long time, and we can use a laptop which is quite happy to work directly on the 160 volt mains to connect to the internet via the modem. The modem seems quite happy with the UPS's waveform on battery.

I just need to know whether the harmonic-laden waveform from a saturating regulating transformer would be any more dangerous to chips in a PC than that from a UPS on battery.

Cheers, + SJ

[Crossy]

I just need to know whether the harmonic-laden waveform from a saturating regulating transformer would be any more dangerous to chips in a PC than that from a UPS on battery.

I doubt very much that there would be an issue, after all you don't get much more harmonic-laden than a cheapo UPS putting out a square-wave

The first thing that your PC power supply does to the incoming supply is rectify and filter it, so the waveform is not an issue so long as its peak value is somewhere near. Theoretically, PC will run on a DC supply of around 300V never tried it though.

Feeding your square-wave into an induction motor (the fan) will give it all sorts of problems as surmised by yourself, hence the noises, I doubt the UPS was too fussed about it either

[paulfr]

Did the mods spike my reply from yesterday ?

==============================

Crossy

The dc power source which runs the high frequecy oscillator which drives the switches and thus the ferrite in a SMPS is NOT itself a SMPS. So unless it has been well overdesigned, a 20 percent dip in the line will probably take it out in exactly the same manner as a linear PS.

The UPS is your protection from line dips and brownouts. If it is not well designed as above, then the battery is going to being working hard. I assume there is hysterysis at the switching point so it is not repeatedly clicking in and out.

Cheers

[Crossy]

Did the mods spike my reply from yesterday ?

The dc power source which runs the high frequecy oscillator which drives the switches and thus the ferrite in a SMPS is NOT itself a SMPS. So unless it has been well overdesigned, a 20 percent dip in the line will probably take it out in exactly the same manner as a linear PS.

The UPS is your protection from line dips and brownouts. If it is not well designed as above, then the battery is going to being working hard. I assume there is hysterysis at the switching point so it is not repeatedly clicking in and out.

Hmmm, didn't see any reply previously, and I doubt the mods would have removed it unless offensive

Agree 100% with the above, -20% is the bottom end of reliable operation (about 180V on a 220V supply) at that level you'll have almost no protection from skipped cycles. A 'universal' (100-250V) PSU would be far better as they're good to about 80V input.

If you have chronic under-voltage a simple UPS will run its batteries down as they don't normally have the line-boost function that you see in the expensive on-line units and will therefore go on battery too often for the (low) supply to re-charge properly. A simple AVR transformer will boost your line to 220V, use that to feed the UPS which will filter the crap out that the AVR puts in and give you proper brown/black out protection and you're in business

I don't have an AVR, our mains is pretty good voltage wise and I have a (bloody expensive) on-line UPS that's good down to 100v input (apparently, never tried it).

[Mumbo Jumbo]

Interesting subject , but can some one translate it into non technical speak please.. I have my PC connected to a uninterruptible power supply with a stabilizer

Made by powercom, 525VA, purchased here in Thailand , my house voltage fluctuates on a daily basis , the highest ive ever seen the voltage is 232 Volts and the lowest its been down to is 124 volts , my UPS is constantly clicking away and may be once a day it automatically Shuts down my computer . I was thinking of going to the local Electricity office To report the problem, ( show them my UPS print out records ) and ask them what they can do .?, Two questions …

Has any one who experienced this kind of voltage fluctuations been successful

In getting the electricity office to sort things out..?

Is there any thing I can do to help this situation with my UPS clicking away

All day..? can I buy a larger / better type of unit , would this help at all..?

Any other comments welcome …

[paulfr]

Is there any thing I can do to help this situation with my UPS clicking away

All day..? can I buy a larger / better type of unit , would this help at all..?

Depends on what you want to accomplish.

If the UPS is shutting down the PC too much for too long, a larger higher power unit might be able to run on the battery for a longer period and thus not need to shut you down. Also, if your UPS cannot handle lows you see of 124vrms, then a better rated unit would be able to run with that low an input.

I doubt you'll get much help from the local electric company, but it is worth a try if you have the time.

[Mumbo Jumbo]

paulfr..

Thanks for your reply, my UPS normally only keeps the computer running for about Five minuets before it shuts the computer down, the current UPS is rated at 525VA, so would a larger rated UPS say one rated at 1000VA keep the computer from shutting down longer..? and do you know the VA to Time scale ..EG 525VA = 5 minuets stand by time before shutting down.

I also here seem to have a lot of spikes showing up on my USP control panel .... not too sure what that means, and ive had the voltage tested at the house meter just in case the voltage fluctuation problem was due to some thing on the house consumer board.

[Crossy]

Is there any thing I can do to help this situation with my UPS clicking away

All day..? can I buy a larger / better type of unit , would this help at all..?

Depends on what you want to accomplish.

If the UPS is shutting down the PC too much for too long, a larger higher power unit might be able to run on the battery for a longer period and thus not need to shut you down. Also, if your UPS cannot handle lows you see of 124vrms, then a better rated unit would be able to run with that low an input.

I doubt you'll get much help from the local electric company, but it is worth a try if you have the time.

Agreed Paul.

I'd go for a two-pronged approach. You have two issues to address:-

1. Low voltage for prolonged periods
   
2. Power interuptions
   

Atack 1. with a good quality AVR (Automatic Voltage Regulator) which will take your low input and boost it to 220V, they do this without batteries, in effect they are a variable transformer which automatically adjusts the ratio to give a pretty constant 220V. Feed this into your UPS which can then concentrate on its primary function of bridging over actual power failures, point 2.

Once the UPS has a nice solid 220V you may find that it is adequately sized for your application. You MAY be able to install additional batteries to increase the run time, depends upon the UPS itself, cheapies tend not to have this facility.

Edited January 10, 2008 by Crossy

[Mumbo Jumbo]

Hi Crossy

Thanks for your reply, well it looks as if may be I need to look for as you say , an AVR (Automatic Voltage Regulator)

Ive don't think ive ever seen one for sale here , when looking around the Computer IT Mall's , have you seen them here for sale , any idea of the price .. sorry about the hand holding

Mumbo

[Mumbo Jumbo]

Just found this ...

MGE NOVA 1100 AVR (Line Interactive)

4,494 BAHT (VAT included)

Product Description

Power rating 1100 VA / 600 W

Technology Line Interactive with Booster +18% and Fader -15%

Output 4 x IEC*

Input/Output

Input voltage 160 V to 290 V

Output voltage 230 V

Frequency 50/60 Hz auto-detection

Surge protection Total energy dissipation: 220 Joules

Protection Circuit breaker

Data line protection Protection for Telephone/Modem/Internet line

Warranty 2 years

Batteries

Battery recharging Continuous battery recharging,

even if the ON/OFF button is set to OFF

Battery monitoring Battery replacement indicator (red LED)

Replaceable batteries Access via the front panel

Startup without mains power (cold start) Can be used as a mobile power source

User interface 1 illuminated ON/OFF button, 1 Fault and Overload LED,

1 battery Fault LED + audible alarms

at ...... http://www.shop4thai.com/en/product/?pid=12622

Not too sure if this is what's being talked about ..?

Mumbo

[Crossy]

Just found this ...

at ...... http://www.shop4thai.com/en/product/?pid=12622

Not too sure if this is what's being talked about ..?

Sort of, but it has batteres possibly a bit OTT since you already have a UPS.

The things I'm thinking of are in just about any Mom and Pop electrical shop, and are considerably cheaper, Amorn certainly have them and I think I've seen them in HomePro too

EDIT Something like this http://www.line-conditioner.com/SLc-600-12...Conditioner.htm

Edited January 10, 2008 by Crossy

[Mumbo Jumbo]

Thanks Crossy , .. whats Amorm ..?

I will have to scout about in my Local IT mall , Just wondering if any other forum members have

see one of these type of units about any where..?

Thanks Mumbo

[Crossy]

I will have to scout about in my Local IT mall , Just wondering if any other forum members have

see one of these type of units about any where..?

Amorn is THE major supplier of electronic bits n bobs in Thailand, there are several shops around, the biggest being the Old Siam Plaza in Ban Mo (BKK).

You'll probably score better looking in electrical outlets as these things see wider duty than just IT, very good for keeping your air-con going (and prolonging its life) and stopping the lights flickering all the time.

Zeer Rangsit is worth a look if you're in northern BKK.

Where are you located?

[Mumbo Jumbo]

Hi Crossy , again thanks for the info, now I know a bit more about what to look for , I can go hunting.

I am about 90 Km away from Korat , so not a lot of places to look..

Thanks Mumbo

[Mumbo Jumbo]

Well ive looked around our local electrical shops explained what I’m looking for and got a blank stare back, so its off to a bigger Town for another look , just one thing have I got this right, to day my house mains voltage went down to 167 Volts for about 15 minuets and my UPS sounded the alarm so I shut down the computer , If I were to have a AVR plugged into a house mains socket outlet and then take my USP power feed from the output on the AVR , when my house voltage fall again to 167 Volts , the AVR will compensate for the low voltage and supply the UPS with 220Volts ..?, if saying my house voltage drops to 167 Volts and stays at this voltage for a longer period , say 2 Hours , do you think an AVR would supply the UPS with the correct 220 Volts for this length of time..?

Thanks

[Crossy]

Well ive looked around our local electrical shops explained what I’m looking for and got a blank stare back, so its off to a bigger Town for another look , just one thing have I got this right, to day my house mains voltage went down to 167 Volts for about 15 minuets and my UPS sounded the alarm so I shut down the computer , If I were to have a AVR plugged into a house mains socket outlet and then take my USP power feed from the output on the AVR , when my house voltage fall again to 167 Volts , the AVR will compensate for the low voltage and supply the UPS with 220Volts ..?, if saying my house voltage drops to 167 Volts and stays at this voltage for a longer period , say 2 Hours , do you think an AVR would supply the UPS with the correct 220 Volts for this length of time..?

Keep persevering, they're out there to be found.

If you use a unit as I showed earlier, then it will boost your low voltage forever! Because it acts as a variable transformer it simply pulls a greater current from the (low) input so that the input power (VxA) is the same as the output power (less a little for inefficiency).

Feed your UPS with this regulated supply and it should only go on battery if the mains actually goes off

[klikster]

Did the mods spike my reply from yesterday ?

I lost a post here yesterday as well .. glad to know that I'm not going crazy.

[Crossy]

Did the mods spike my reply from yesterday ?

I lost a post here yesterday as well .. glad to know that I'm not going crazy.

Perhaps you could both re-post your responses, any and all ACCURATE information is most welcome

Posts don't normally get deleted unless offensive, and there's usually a mod. note included in the thread, maybe technical issues.

Edited January 12, 2008 by Crossy

[tjo o tjim]

The reason for putting an AVR upstream of a UPS is because it has a wider range than the UPS itself. The UPS mainly just provides battery backup, not really regulation. A PC doesn't need the regulation, but much of your other equipment might. Given that the problem is lack of capacity, the most appropriate way to deal with it is to reduce load as voltage drops. A good old incandescent bulb does just that, as does an induction motor. Unfortunately, much of the other toys we have today don't.

Crossy's point on the 300VDC-- that's actually the most efficient way to power a PC; I think it is 380VDC per LBNL. Unfortunately, if you give 300VDC input power, the power supply isn't as tolerant of voltage fluctuations (I think it drops to +/-3%, but haven't seen definitive details).

If you are OK with your PC losing power (just want to protect against voltage variation), the SMPS internal to it is going to be just fine. There are ways to provide battery backup to the 12V rails to make things work through an outage, but it doesn't always work just right, so you get stuck with a UPS.

[Crossy]

If you are OK with your PC losing power (just want to protect against voltage variation), the SMPS internal to it is going to be just fine. There are ways to provide battery backup to the 12V rails to make things work through an outage, but it doesn't always work just right, so you get stuck with a UPS.

One major plus using the AVR is that it will keep your UPS batteries well charged for when you actually do lose power. The better ones will keep the output at 220V even if the input is down near 150V, I seriously doubt that a PC power supply running near its max output (aren't they all) is going to hold up at that input level.

I remember those 'internal' UPS's from some years back, are they still available considering the increasing number of supply rails and currents being used?

[zzSleepyJohn]

Well ive looked around our local electrical shops explained what I'm looking for and got a blank stare back, so its off to a bigger Town for another look , just one thing have I got this right, to day my house mains voltage went down to 167 Volts for about 15 minuets and my UPS sounded the alarm so I shut down the computer , If I were to have a AVR plugged into a house mains socket outlet and then take my USP power feed from the output on the AVR , when my house voltage fall again to 167 Volts , the AVR will compensate for the low voltage and supply the UPS with 220Volts ..?, if saying my house voltage drops to 167 Volts and stays at this voltage for a longer period , say 2 Hours , do you think an AVR would supply the UPS with the correct 220 Volts for this length of time..?

Keep persevering, they're out there to be found.

If you use a unit as I showed earlier, then it will boost your low voltage forever! Because it acts as a variable transformer it simply pulls a greater current from the (low) input so that the input power (VxA) is the same as the output power (less a little for inefficiency).

Feed your UPS with this regulated supply and it should only go on battery if the mains actually goes off

I may be stating the obvious, but since 167v is getting into the realms of a "dark brown" brown-out, it would be important to check the AVR spec to make sure it can cope with a voltage that low, or whatever the lowest you've ever measured actually is. I'm not sure if they all go that low.

+ SJ

[Crossy]

I may be stating the obvious, but since 167v is getting into the realms of a "dark brown" brown-out, it would be important to check the AVR spec to make sure it can cope with a voltage that low, or whatever the lowest you've ever measured actually is. I'm not sure if they all go that low.

Good point, they don't, that's why I used the word 'good'.

The one that I linked to (dunno if it's available here but I'm sure something similar is) is good down to 150V, I assume it will simply stay on maximum boost if the supply continues to fall until eventually the output drops below the UPS threshold and it kicks in.

EDIT The one referenced is a tap-switching unit, I have no idea how the ferro-resonant (cheap) units behave as the input falls outside their operating range.

Edited January 12, 2008 by Crossy