Coping With Low Voltage Mains

[zzSleepyJohn]

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

This thread has developed quite interestingly and usefully into a discussion about AVRs, but in doing so has rather drifted away from the question in my OP, where I asked about saturating transformer regulators which, if I've understood correctly, would be a cheaper option than a modern tap-changing AVR.

Given now that we believe a PC power supply should be able to cope with a bad waveform, what actual benefit would there be in spending more for an AVR rather than using an old-fashioned saturating transformer? OK, I can think of one; lower heat loss in the core, but is there anything else?

Has anyone got, or does anyone actually have experience of using a saturated core transformer as a regulator?

+ SJ

[Cuban]

Gentlemen, you are debating a fixation focused on maintaining "mains" voltages, where as the question was asking about PCs. As this has become a techie debate I am suprised I am the first to suggest the real cure (although beyond what many would consider worth doing) which is the build a lead-acid battery based PC power supply unit which gives reserve capacity for running the PC for hours (depending on battery size and PC usage). You would need two 12 volt batteries to provide the -12volt supply, floating earth. (Link for PC power requirements.) then simply trickle charge the lead acid using your dirty incoming mains supply.

There is little point using a 12 volt battery to step up to 220 volts just to step down to +/-12 5 and 3.3 volts again.

Ah. what about the monitor I hear you ask, many LCD monitors run from their own switch mode PSU so accept 12volt inputs already. Likewise with ADSL routers etc.

I've considered a set up like this for my upcountry house, but as yet it is not neccessary to go to the effort required. Likewise the generator project is on hold as the one power cut in the area last year did not affect us.

My concern is running air-con during a prolonged power outage (maybe the freezer) and the best solution is to rig up some type of portable unit - maybe ripped out of a truck so it to can run from a 12/24volt supply.

[Crossy]

Given now that we believe a PC power supply should be able to cope with a bad waveform, what actual benefit would there be in spending more for an AVR rather than using an old-fashioned saturating transformer? OK, I can think of one; lower heat loss in the core, but is there anything else?

The 'saturation' or 'ferro-resonant' units don't cover such a wide range of input voltage, if you only have brownouts rather than dark-brownouts then I see no issues with using one.

[Crossy]

Gentlemen, you are debating a fixation focused on maintaining "mains" voltages, where as the question was asking about PCs. As this has become a techie debate I am suprised I am the first to suggest the real cure (although beyond what many would consider worth doing) which is the build a lead-acid battery based PC power supply unit which gives reserve capacity for running the PC for hours (depending on battery size and PC usage). You would need two 12 volt batteries to provide the -12volt supply, floating earth. (Link for PC power requirements.) then simply trickle charge the lead acid using your dirty incoming mains supply.

There is little point using a 12 volt battery to step up to 220 volts just to step down to +/-12 5 and 3.3 volts again.

Ah. what about the monitor I hear you ask, many LCD monitors run from their own switch mode PSU so accept 12volt inputs already. Likewise with ADSL routers etc.

Actually you need to provide +12V +5V +3.3V and -12V to keep a modern PC running, if you look at your PSU you'll see the currents required, they are quite frightening, certainly outside the realms of simple linear regulators (gonna get VERY hot).

The simple solution which does not pose any risk of frying your PC with amateur electronics is a commercial UPS backed up by an AVR if you have wide mains fluctuations.

If you DO decide to go for a DC solution, it would probably be better to provide 300-320V DC to the mains side of the PC's PSU, you can then use the SMPS's regulation system.

I agree that it seems counter intuitive to jack 24V up to mains only to regulate it back down, in fact, if you look in large data centres with lots of servers, they all run off 48V DC from a system exactly as you describe, a bloody great lead-acid battery with a charging system (each server has an SMPS designed to take the 48V input an provide the internal voltages).

EDIT You CAN get regular sized PC PSUs that accept 48V DC like this on http://www.powerstream.com/DC-PC-48V.htm so the 48V solution is actually viable for an off-grid situation, it would certainly be more efficient.

Better yet, Powerstream also make regular ATX size PSU for both 12V and 24V input that would suit a solar/wind/micro-hydro off-grid system.

Edited January 12, 2008 by Crossy

[Mumbo Jumbo]

Hi Crossy

This AVR is still not a Mom and Pop electrical shop model , but from the same Thai company who I bought my current UPS from…

http://www.powermatic.co.th/downloads/prod_dl.htm

click on TAP-Change AVR ....... what do you think of the spec..?

Thanks Mumbo

[Crossy]

http://www.powermatic.co.th/downloads/prod_dl.htm

click on TAP-Change AVR ....... what do you think of the spec..?

I would like to see a second boost stage but out in the boonies beggars can't be choosers, it should do the job quite adequately.

Input 220V +- 20%, so it's good down to about 176V input.

Lets assume that at 176V (-20%) the output will be at the lower specified limit (-7%) meaning that the output will be around 204V, thus we have a boost ratio of 1.16x.

Because it's a tap changer it should continue to work at maximum boost even if the input goes lower than that, at 160V input the output will be about 185V which should still keep your PC / UPS quite happy (much happer than it would be on 160V).

The big question, how much is it?

EDIT to correct calculations.

Edited January 13, 2008 by Crossy

[tjo o tjim]

A saturating transformer is just a very inefficient way to solve the problem, which is why most of the suggestions move away from that path. They also have challenges in many environments which in the end can make the tap changer a more effective solution.

The AVR really isn't anything fancy

For a while, Google was fronting a company that made 12V input power supplies suitable for PCs; don't know if Crossy's Powerstream is comparable. Google was running their data centers with centralized 12V converters at each rack, actually pretty effective.

Mumbo's AVR is much fancier than anything I have seen before in Thailand, but should do the job. Usually they look like big brown boxes, and are available in the Mom and Pop shops.

[Crossy]

A saturating transformer is just a very inefficient way to solve the problem, which is why most of the suggestions move away from that path. They also have challenges in many environments which in the end can make the tap changer a more effective solution.

For a while, Google was fronting a company that made 12V input power supplies suitable for PCs; don't know if Crossy's Powerstream is comparable. Google was running their data centers with centralized 12V converters at each rack, actually pretty effective.

Mumbo's AVR is much fancier than anything I have seen before in Thailand, but should do the job. Usually they look like big brown boxes, and are available in the Mom and Pop shops.

Agree 100% Tim, a tap changer is THE solution, although like I said above, I'd like to see another boost tap (2 boost stages rather than 1).

I suspect that Google were using 48V servers (not 12V, but I coiuld be wrong) as that's the industry standard. 48V is low enough to be classed as non-hazardous (the limit is 50V) but high enough that the currents required are manageable.

[Mumbo Jumbo]

Thanks Crossy, I will ring the company on Monday and get the price

Thanks Mumbo

[Mumbo Jumbo]

Well Crossy to answer your question ....... The big question, how much is it?

Just spoke to the company in Bangkok and the sales girl said the Model .. TCA-1200 ( 1200VA )

is priced at ... 1,800 Baht and available from most IT Mall's , so I'm off to the local IT Mall to have a look

to be honest not too sure about the price quoted so will report back..

Mumbo

[Mumbo Jumbo]

Well after looking around I found the Tap – Change AVR Units for sale at the IT Mall , they were priced at..

Mode.. TCA-1200 ( 600 Wat) 1,300 Baht

TCA-2000 (1000Wat) 1,750 Baht

So I bought a TCA-2000 , its been in use now a few days supplying power to my UPS and up to now its worked OK, my UPS has stopped clicking and the UPS Voltage readout software shows less voltage fluctuations Ive had a Volt meter connected to the same wall socket out let supplying the AVR just to see what the voltage was supplying the AVR , and the voltage has been as low as 180 Volts and up to 224 Volts . so all in all I’m pleased with this unit .

[Crossy]

Well after looking around I found the Tap – Change AVR Units for sale at the IT Mall......

....... the voltage has been as low as 180 Volts and up to 224 Volts . so all in all I’m pleased with this unit .

Low voltage mains coped with, job's a good 'un

QED.

[Mumbo Jumbo]

Thanks Crossy

Its a good feeling when some thing here turns out OK .. I am wondering now if my Fridge / freezer would run off one one these AVR's as the motor is constantly going up and down as the house voltage moves up and down ..?

Thanks

[Crossy]

Its a good feeling when some thing here turns out OK .. I am wondering now if my Fridge / freezer would run off one one these AVR's as the motor is constantly going up and down as the house voltage moves up and down ..?

It most certainly would, here in Barely-Credible India they run the aircons off these units, look like cheapo ferro-resonant types (not tap switchers).

Now you know what to look for have a deeper search in the electrical places, I'm sure you could get a unit suited to your fridge for less than you paid for the posh one for your PC. It would probably be worth it in better reliability / life of your fridge motor

[Mumbo Jumbo]

Thanks again Crossy..

Well now I know what sort of thing to look for I can scout the electrical shops a bit more, and will report back ..

Thanks ...

[Upcountry]

Well, I had a rather lucky day yesterday, considering.

While I was out there apparently was a power outage of sorts. If I go away for a day, I usually shut things down (but leave the UPS's on, unless it is for two days or more). I was out longer than planned. Had a computer running. I knew there was an outage for a couple of reasons, but the obvious one was that one of my Powermatic PCM power supplies had burned up (awful smell). Luckily the one with the computer was fine, but this is the second time I've had this problem with a three/four year old PCM.

The previous time was when I turned off the circuit breaker by mistake. I called the company about it, and they thought maybe just the transformer (and fuse setup) might be bad. $1k baht to get replacement parts, plus shipping. But they didn't get my email right (of course) for a 'quote' and I think I should probably send the unit to them for diagnostics anyway.

But now I have two of the same model that have blown up, and a third that will certainly be next. I'm supposing that the cause is either that a power surge somehow overwhelmed the circuit breaker, blowing the unit - or else it may be batter/logic related somehow. The units have worked for several years with battery replacements.

Living up country, it is impossible to find equivalent replacements. I can get single battery units at the hypermarts, etc., but the local electronics stores seem to sell crap. The two-battery units don't have the capacity of the PCM's.

Basically, I'm wondering if I should just get the basic one-battery units (and use more wall plugs). Any recommendations on the best UPS's to buy here?

-UC

/ps - I do use grounded three-prong wall plugs. ;-)

[Mumbo Jumbo]

Hi, Upcountry

Interesting story , I also have a Powermatic PCM UPS ( Model Imperial Series IMD-525AP ) and Upsmon power management software , which ive been running for Two years now and in the last few day's ive changed the internal battery ( 700 Baht ) I also now use an AVR unit to supply the UPS as my house voltage fluctuates on a daily basis, which was causing the UPS to be constantly switching every few minuets, now the AVR supply's the USP , the UPS constant switching has stopped .

My next thing is to install a second external USP battery in parallel l to increase the length of the USP backup time , Ive as yet never left the house with the computer running so Ive never seen just what happens in this situation, I all way's thought that if the power was cut to the USP, it would automatically shut down the computer and then turn its self off, if thats so I wonder why your switched off UPS has burnt out ..?, and as you say it happened a second time when you turned off the circuit breaker by mistake , should the UPS on detecting you turned it manually off ( as a power cut )it would then ,give a warning signal and then just go through the routine of a shutdown procedure by its self, I wonder why it would burn out by only manually turning off of the circuit breaker.

If the problem does lie with a possible overwhelmed circuit breaker may be supplying the UPS with a AVR may do the trick, my house voltage fluctuates from the lowest ive recorded which is 124 Volts to the highest of 312 Volts and the AVR has been coping with this voltage difference OK

Mumbo

.

[Mumbo Jumbo]

I forgot .. Any recommendations on the best UPS's, I keep hearing about APC Units here..

http://www.apcc.com/products/family/index.cfm?id=21

and some General info here....

http://www.pcguide.com/ref/power/ext/ups/types.htm

Mumbo

[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.

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.

Well, I know you didn't like some of my 'info' (in another topic), Crossy .. but your is not always accurate either. So who here is to determine what information is accurate and what is not?

[Upcountry]

Mumbo Jumbo, thanks for your response and the links.

My PCM's are model number 04Y050157.

They are 1,000 watt units with five three prong outputs.

I could never get the Upsmon software to work with my XP machines. I also have a Mac, plus other things are plugged into them. So the auto-off feature hasn't been practical for me.

In all other instances, when the power is cut by outage or circuit breaker, the UPS's just start beeping. In the even of an outage, my protocol is to A) curse, "Not-a-F####-ing-gain!" and wait for a few moments, with "Please, come back on, please please!" , then c) start shutting down, finally D) turn off the UPS's. I've never witnessed the machines running out of battery power.

I still don't get the circuit breaker instance. The air conditioner maintenance people wanted me to turn off the breaker for the air con. Once that was done, no beeping, I didn't realize there was a problem until one of the workers came downstairs to get me, to say that something was burning. Not till I saw the error light did I realize the UPS was at fault. I unplugged it. Later, when I plugged it in again, of course another pop, more smell.

It's interesting that only one of the PCM's failed the other day when I was out. All other UPS's I have, including single battery ones were fine. No beeps or lights to indicate low battery.

Now I'm thinking that UPS's just wear out over time, so that they can't handle the outage or possible surge when the power comes back on. Of course, the circuit breaker should deal with a surge that is beyond what the UPS can handle, right?

Even though I live in an urban area, I assume that my power is fluctuating too, so maybe an AVR would be a good idea for me as well. Would this work for the entire house, or just certain circuits?

UC

[Upcountry]

Hey, has anyone bought a UPS on-line, here in Thailand?

So far I can't find them via any online shopping websites. Only power strips.

UC

[kingq]

Interesting read for me. Does anyone know of any voltage regulators and where I can buy one that is placed in at a point between the main power line from the meter and my circuit breaker panel?

[Mumbo Jumbo]

Hi kingq , when I was hunting for a small AVR unit , I went into a large electrical shop, and asked about a small AVR unit to connect to my computer, my translation

was not too good, and the shop guy came back with a '' large '' in line AVR unit like you are describing , so I did not take too much notice of it, so yes they do seem to sell the large AVR units here , sorry I can't be more helpful ..

Mumbo

[Upcountry]

Well, here's an update to my stories above.

I finally got the electric company techs out here to look at my problem. They rearranged the circuits so that the air conditioners are on a separate line form the office outlets. The fact that the a/c was involved might explain my UPS burn-outs.

I was able to speak English with a Powermatic engineer (may have mentioned that above) regarding getting my units repaired. I also asked his advice about protecting my DVDR and TV, etc. He recommended thier SMK-600A for them, because the put out a sine wave instead of a square wave. He explained that the QUN and KIN UPS's might damage my non-PC equipment over time. I'd heard something along this line in the past, so I went along with that.

He also recommended the TCA-1200's for my audio equipment, since the don't really need a UPS. The total bill was rather high for everything I needed, but I only paid 1,100 for each of two TCA-1200's. Based on comments above, I think I got a good deal on them, as well as my other stuff, buying directly.

It was a HUGE pain dealing with the sales department with limited Thai, but eventually a good English speaker got on the line with me and helped me out - he could have been the CEO, for all I know!

At any rate, I wonder if Crossy and others can confirm that quality UPS's with a built-in AVR (the Powermatic units have them, per the engineer - hence no need to put them between the wall and the UPS) can preclude the need for an AVR as suggested in earlier posts.

Thanks,

-UC

[grtaylor]

I may be missing something - but I don't really understand this thread. I've never had a problem with the mains electricity here - its either ON or OFF . . . . .

[Crossy]

At any rate, I wonder if Crossy and others can confirm that quality UPS's with a built-in AVR (the Powermatic units have them, per the engineer - hence no need to put them between the wall and the UPS) can preclude the need for an AVR as suggested in earlier posts.

Yup, if your UPS has a built-in AVR there is little point in adding a seperate one

[Meerkat]

Many thanks to all who have contributed in this and the other AVR/UPS threads.

After yet another power-cut this morning (after the one yesterday evening), I decided that I should get with the programme and finally get some protection sorted - some of my gear, especially the Dreamboxes, really doesn't like surges/cuts. Went for the Powermatic TCA-2000 and the APC CS500. Prices in Data iT in Zeer Rangsit were 1,799 and 2,650 respectively. Had I read Upcountry's post above I'd have gone direct to Powermatic to get the Tap Changer a bit cheaper, but with no power to connect to the internet this morning...

Minor point to anyone looking at the APC units. The sockets are of the same type as you see on PC/printer power leads. If you want to connect anything else, you'll need an adaptor. Data iT had some power strips that instead of the usual fixed lead to a normal plug, use a lead with the same design as the APC sockets, so you can use it to connect your router/sat box etc.

Hopefully this belt-and-braces approach will keep everything humming along smoothly - thanks again all! Sadly for the rest of you I think Crossy lives closest to me, so he'll just have to have all your thank-you beers himself...

[Crossy]

Hopefully this belt-and-braces approach will keep everything humming along smoothly - thanks again all! Sadly for the rest of you I think Crossy lives closest to me, so he'll just have to have all your thank-you beers himself...

Edited May 29, 2008 by Crossy

[zzSleepyJohn]

Yup, if your UPS has a built-in AVR there is little point in adding a seperate one

Dunno, just to get a last word in here, I reckon there could be some point if someone is stuck on the end of a long distribution line. This is because run-of-the-mill UPSs with a built-in AVR centre their +/- 25% input voltage range on 220v, i.e. they can cope from 165v to 275v.

But usually the voltage drops rather than rises, so the +25% of that input range is wasted. I know of a case, probably not all that rare in rural locations, where the incoming mains normally sits at around 180v, and quite often browns down to well below 165v. In this kind of situation, I'd suggest a seperate AVR could make a big difference.

+ SJ

[Crossy]

Yup, if your UPS has a built-in AVR there is little point in adding a seperate one

Dunno, just to get a last word in here, I reckon there could be some point if someone is stuck on the end of a long distribution line. This is because run-of-the-mill UPSs with a built-in AVR centre their +/- 25% input voltage range on 220v, i.e. they can cope from 165v to 275v.

But usually the voltage drops rather than rises, so the +25% of that input range is wasted. I know of a case, probably not all that rare in rural locations, where the incoming mains normally sits at around 180v, and quite often browns down to well below 165v. In this kind of situation, I'd suggest a seperate AVR could make a big difference.

Ok, you win

Absolutely correct in this case, I did say 'little point' rather than 'no point'

Edited May 30, 2008 by Crossy