Low Voltage

[Dakling]

Not sure what's going on but my UPS has started popping and whistling and crackling constantly. Based on its readings I am only receiving 205 volts. How can I safely check if my UPS is right or wrong.

For instance if I try test the mains power on the front end of my breaker box with a cheap voltmeter am I gonna blow it up and burst into flames or should it be a non issue? Can I just shove the probes into the live and neutral slots in another socket and check there. Is it possible that the voltage on one zone is gonna be out of whack with the voltage coming in from the mains.

Lastly if I convince myself that I am receiving a low voltage from the meter, what can I do? I am in a tiny village in the middle of nowhere, is it possible that our whole village and area is only running on 205 volts?

Thanks for any and all suggestions

[wayned]

You can easily check the power using a voltmeter at any socket. The cheap one's work fine, but don't "shove the probes" in any socket, be careful you are working with potentially deadly voltages, you could "blow it up and burst into flames" or worse!

I live in a remote village in the middle of nowhere and the power normally fluctuates between 190 and 225 vac, it;s a way of life. If it goes lower you will see the incandescent lights dim and the first thing that I do is turn off my water pumps - they don't like low voltage. I don't have UPS on my computer and it handles the normal swings but our power goes off for a short period at least once a day and I loose whatever I'm working on but back up often. The outages and low voltage affect the entire area not just my home.

[Crossy]

I'm a bit worried that the UPS is "popping and whistling and crackling" is that an electrical noise (worrying, possibly a loose connection) or is it a 'proper' UPS beeper warning?

[Dakling]

I'm a bit worried that the UPS is "popping and whistling and crackling" is that an electrical noise (worrying, possibly a loose connection) or is it a 'proper' UPS beeper warning?

Combination of the warning and the thing clicking as it switches from charging to supplying.

[Crossy]

I'm a bit worried that the UPS is "popping and whistling and crackling" is that an electrical noise (worrying, possibly a loose connection) or is it a 'proper' UPS beeper warning?

Combination of the warning and the thing clicking as it switches from charging to supplying.

No problem then, you can use a cheap meter on an AC range above 300V to check your supply at the outlet and, to be sure, at the incoming supply in your distribution board.

Take care, poking around with the power on is potentially lethal!

If you determine that the supply is low, and stays low, time to talk to the supply authority (good luck there).

You can improve the situation of the UPS clicking in and out by putting an AVR (automatic voltage regulator) or stabiliser between it and the supply outlet. Your local electrical emporium should be able to help with one of those.

[seedy]

One way I have solved the issue with electronics - expensive ones anyway - is thru the use of an inverter.

Main power in goes to a battery charger - which do not seem to be very picky about voltage or frequency. This keeps a pair of batteries charged, which in turn power an inverter.

Sensitive electronics run on the inverter. Any power surges, brown-outs, etc are now seperated from the main power coming into the house.

[Daffy D]

wayned, on 14 Jan 2014 - 04:39, said:

You can easily check the power using a voltmeter at any socket. The cheap one's work fine, but don't "shove the probes" in any socket, be careful you are working with potentially deadly voltages, you could "blow it up and burst into flames" or worse!

I live in a remote village in the middle of nowhere and the power normally fluctuates between 190 and 225 vac, it;s a way of life. If it goes lower you will see the incandescent lights dim and the first thing that I do is turn off my water pumps - they don't like low voltage. I don't have UPS on my computer and it handles the normal swings but our power goes off for a short period at least once a day and I loose whatever I'm working on but back up often. The outages and low voltage affect the entire area not just my home.

Having the computer crash like that is not good for the Hard Drives. The heads don't have time to park

Invest in a UPS your HDD will love you for it and you will not loose your work and if a power out happens at night you have enough light from the monitor to scramble for the candles.

[Crossy]

One way I have solved the issue with electronics - expensive ones anyway - is thru the use of an inverter.

Main power in goes to a battery charger - which do not seem to be very picky about voltage or frequency. This keeps a pair of batteries charged, which in turn power an inverter.

Sensitive electronics run on the inverter. Any power surges, brown-outs, etc are now seperated from the main power coming into the house.

That's the topology of an (expensive) on-line UPS seedy. The problem with doing it this way is that your battery charger has to supply the load energy as well as charge the battery = big expensive battery charger.

Plus is of course better isolation from nasties and no switch-over time.

[seedy]

The problem with doing it this way is that your battery charger has to supply the load energy as well as charge the battery = big expensive battery charger.

Plus is of course better isolation from nasties and no switch-over time.

If memory serves the battery charger was only around 2000 baht.

Can not seem to find good deep cycle batteries here - back in 'The Colonies' I had some nice 2V ones, 60kg each, salvage from an old telephone switchboard.

Here have to make do with regular automotive batteries.

On my list next time I go back is to have a 2000W pure sine wave inverter made for the 220V 50Hz here.

Keep my precious pieces fully protected. But I must say that the modified sine wave inverter I am using seems to do OK

[Crossy]

How many Amps is that 2,000 Baht charger?

[thomasteve]

One advantage laptops have is that the power supply 'brick' they use are rated between 110 to 240 V so wide voltage fluctuations are tolerated.

[seedy]

How many Amps is that 2,000 Baht charger?

20 A . Not a fully automatic charger, so is on a timer. Once a month - if I remember !! - I get out the voltmeter and check the battery voltage.

Used a hydrometer with the larger low voltage cells as they liked to be only discharged 25% of capacity and had a good built-in Trace charger which would keep them happy.

[seedy]

One advantage laptops have is that the power supply 'brick' they use are rated between 110 to 240 V so wide voltage fluctuations are tolerated.

True. But if the frequency changes a lot - like in a brown-out - I have had them fail.

Or last year one of the neighbors tried to steal power, caused the voltage to spike way over 220 V. Lost a few of those cube-style chargers for portable stereo and fone chargers - and they were multi-voltage too.

Floor fan sure turned fast tho' !!

[Dakling]

You can improve the situation of the UPS clicking in and out by putting an AVR (automatic voltage regulator) or stabiliser between it and the supply outlet. Your local electrical emporium should be able to help with one of those.

A couple of follow up questions.

I have been looking into this on the internet and despite being way above my head in understanding the finer points, I see most "experts" claiming that to get "proper" regulation you have to spend allot of money. I see units being discussed at around 30,000 baht. This seems very expensive to me, (about the cost of the components I want to protect).

I have been watching the UPS pretty closely lately as it has a voltage display window that shows input and output voltages. The input voltage has remained relatively consistent between 200 and 205 volts. Basically what seems to be happening is that the Input and Output will be matched at appox 200v for a minute or so then the UPS will switch the output to 240v for a minute and then it will drop back to the 200v input voltage. I am assuming this is the UPS switching back and forth from charging to supplying modes. Is this hard on the UPS?

Since Thailand's mains supply is only supposed to be 220v (or so says Wiki), is 200v mains supply really that low for my computer and other electronics? The computer is energystar compliant and automatically switches from 120v to 240v so does the 200v supply bother it? I am not sure why the UPS I purchased in Thailand is trying to pump the output voltage to 240v since the normal mains is supposed to be 220v. Would I be better off bypassing the UPS so I have a consistent (albeit low) voltage supply.

Another issue is that with the low voltage, I would imagine I am not likely getting a clean 50hz either, does a standard UPS clean up the frequency issues? How can I check this? Does it really matter?

So far I have only had one real iisue that might be related to the power supply, despite being powered through the UPS my computer had a power supply failure after about 4 months of low voltage power. The power supply was about 4 years old so this might not be considered an abnormal life cycle I don't really know.

Sorry for the pile of questions, I know just enough about this stuff to get myself confused so any hints are greatly appreciated.

[Daffy D]

Sometimes an answer to fairly simple question somehow gets over complicated.

I have 2 computers each protected with a UPS costing about 2000bt. Both have been working just fine for years, though I would imagine the older one may need a new battery soon..

When there is a momentary drop in voltage the UPS will click a couple of times till the voltage is stabilized again. When the power goes out it will beep and gives me a few minutes to save any work (scramble for the candles) and switch off.

It's not rocket science

[Crossy]

OK, 200V is not really low for a 220V supply, about 9%.

I suspect your UPS is being a little 'enthusiastic', is there any configuration in the UPS software so you can set it to 220V? If so that may be enough to stop the hunting.

You should be able to get an AVR that protects just your PC, say 1000VA, for 3-4k Baht, talk to your local electrical emporium about a 'stabilizer', put it between the wall outlet and the UPS so the UPS is getting stabilised power.

[seedy]

As a follow-up - went to Amorn electric, they now have true deep-cycle batteries, 5600 or 5900 baht, can't remember which.

Also have pure sine wave inverters, 12V or 24V inputs, 2000W capacity, 14,000 baht.

May just have to invest in one - and the batteries for sure.

Forgot to take a pic for the specs - will post when I head down that way again.

[Forkinhades]

^ hhmm at those prices it could be better to build your own.

[wayned]

^ hhmm at those prices it could be better to build your own.

^hhmm Even if you supplied a detailed schematic i am just envisioning looking at the end item if someone who never had a soldering iron in his hand built it and was about to hook it up! NEW YEARS EVE all over again!!

[Forkinhades]

You dont need a soldering iron

[wayned]

Just curious! How would you build it without a soldering iron? Wire nuts?

pure sine wave inverter.doc

Edited January 21, 2014 by wayned

[seedy]

I can not read electrical schematics, but have been pulling wrenches and doing auto, hd truck and equipment wiring all my life.

How difficult to obtain the parts here in LOS ???

[wayned]

I'm sure that parts, or at least equivalents, are available here, but if you don't know what you are doing I would not recommend trying to build it. I was just being facetious and asking the fork in hell how he would build it without a "slobering" iron. I'm sure that you could build one for less than 14k baht but sourcing the parts would be a PITA if you didn't have the right connections.

[Crossy]

3-500 notes for a 'proper' 2,000W pure-sine inverter seems to be about the right price, pseudo or modified sine inverters go for a lot less, but a lot of kit doesn't like the waveform.

The simple unit that wayned referenced has more than a few issues, doubtless you could build it for much less, and it's a great hobby experiment (that's perfectly capable of killing you), but:-

1. As shown the output is nowhere near 2,000W (nearer 200W), you need parallel output devices (and current sharing resistors since it's using bipolar devices) and a different transformer to get there
2. It has no output voltage regulation
3. It has no over-current or over-dissipation protection, it will just keep going until it fries the output devices
4. Since the PIC outputs RB5 and RB6 are digital I doubt it's really 'pure sine', possibly, if the firmware is doing fairly high-frequency PWM, it may approximate by relying on the transformer as a low-pass filter
5. You need to program the PIC, one assumes that the firmware is available on the page from whence the diagram came

All great fun, in the past I would have built it, now I'll just go and buy one.

[wayned]

I only posted the schematic to ask "Forky" how he would build one without a "slobering" iron, not a diagram for anybody to build one. The power stage would definitely have to be changed to provide the wanted 2000W and output voltage regulation and current protection. I didn't mean to start a design review!

[Crossy]

I only posted the schematic to ask "Forky" how he would build one without a "slobering" iron, not a diagram for anybody to build one. The power stage would definitely have to be changed to provide the wanted 2000W and output voltage regulation and current protection. I didn't mean to start a design review!

Why not, I'm bored doing real design reviews?

[seedy]

Crossy - what would we do without you !! Excellent as always.

I did not find 14K to be too bad - do not know who the maker is as Amorn has their name on it.

My overseas one is a Trace, now bought out by Xantrex. Had it for years and never a problem.

[Crossy]

Crossy - what would we do without you !! Excellent as always.

I did not find 14K to be too bad - do not know who the maker is as Amorn has their name on it.

My overseas one is a Trace, now bought out by Xantrex. Had it for years and never a problem.

I saw the Amorn units in passing, didn't notice what the peak output of the 2000W unit was, I don't suppose you did?

I'm in the market for a 24V pure-sine unit of about 2kW, but my loads are pretty poor PF (CFLs). My current 2kW pseudo-sine unit objects if there are too many (even a couple of hundred Watts worth), it happily runs the kettle.

[wayned]

Forky's unusually quiet Is he still trying to figure out how to build it with "pop rivets" and no "slober"? When my power is off, my "CFLs" are candle powered and the "kettle" is powered by charcoal.

[Forkinhades]

Forky's unusually quiet Is he still trying to figure out how to build it with "pop rivets" and no "slober"? When my power is off, my "CFLs" are candle powered and the "kettle" is powered by charcoal.

Out on site working

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