Time to buy a UPS (Uninterrupted Power Supply) Suggestions?

[PhotonWrangler]

One of the lesser understood causes of voltage spikes during power blackouts happens when the power goes off, not when it comes back on. At the instant that the AC transformers in line-powered devices are de-energized, the magnetic field suddenly collapses, inducing a sharp spike onto the line.

You can easily prove this yourself -

Find a pair of magnetic headphones, a neon bulb, a 9v battery and some alligator leads. Connect the neon bulb in parallel with the headphone's contacts. Then connect that parallel headphone-bulb combination across a 9v battery. Then disconnect the battery, and the neon bulb will flash at the very moment that the headphones are de-energized. The collapsing field in the headphone's coils produces a voltage spike that's waaaaay above 9 volts, enough to fire the neon bulb!

Oh by the way, do this with insulation between the leads and your fingers, otherwise you'll get a brief shock.

The point? Power energized = 9 volts. Power suddenly de-energized = voltage spike that's MUCH higher than the original applied voltage. Now imagine that incoming power line with all of those transformers, fridge motors and other coils connected across it - many collapsing magnetic fields causing a huge spike that's much higher than the original 120 volts. By the time the power goes off, you've already taken a huge spike.

 

[Brock]

As Ted alluded to modified sine wave inverter also is typically less efficient overall. Also if you run a motor on a MSW inverter you will draw about 15-20% more power compared to running it on a true sine wave inverter. So if the modified sine wave inverter is 10% less efficient and the motors is pulling 20% more you're already 30% behind where you would be with a true sine wave inverter. Also that extra power in a motor turns in to heat typically causing a motor to fail sooner then if run on sine wave.

 

[Handlobraesing]

As Ted alluded to modified sine wave inverter also is typically less efficient overall. Also if you run a motor on a MSW inverter you will draw about 15-20% more power compared to running it on a true sine wave inverter. So if the modified sine wave inverter is 10% less efficient and the motors is pulling 20% more you're already 30% behind where you would be with a true sine wave inverter. Also that extra power in a motor turns in to heat typically causing a motor to fail sooner then if run on sine wave.

Modified square wave inverter is more efficient. The inverter circuit only have to be able to operate the output transformer in on and off. The primary is almost always center tapped and the MOSFETs apply power to the two taps alternatingly with a pause in between.

Sinewave inverter is much more complicated and the conversion isn't as efficient, so given the same battery pack, you won't get as much runtime. AC motors don't like them and it's not good to use with audio equipments (because it makes audible switching noise), but it's just fine for computers.

This UPS gives reasonable runtime and adequate capacity for most home systems.
http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BE750BB

 

[TedTheLed]

bob gudgel
OutBack Power:

"...It's interesting how many things have trouble with modified sine wave inverters. Usually, they're more of a modified square wave but the industry has called them mod sine wave for years.

Some appliances like most microwave ovens rely on the higher peak voltage of a true sine wave and will not cook as fast on modified square waves.

Also, a lot of things expect the smooth slope of the sine wave so that their triac-light dimmer type circuitry will work properly. I think this is why some electric blankets will not work on mod square wave. They used to just turn on and off as I remember to regulate temperature.

Bread makers sometimes won't work. Some coreless drill chargers will break (De-Walt comes to mind) when plugged into mod-square wave sources.

Some RCA small dish receivers won't work. Square wave inverters make noise too lots of times... Audible acoustic and electric noise. Hi-Fi's and audio equipment can be noisey. Some computers will not work either although I haven't personally seen one that didn't.

Motors usually like sine waves better. Motors can run warmer on mod-square.

Usually the battery chargers built into mod-square inverters , if they have a charger built in, will normally be of the Triac light dimmer type and will have a low power factor and draw big current peaks, requiring larger than normal generators for battery charging as well as causing lots of electrical noise..."

also true sinewave IS more efficient than modified square wave, by about 20% -- google it and find a dozen confirmations.

 

[Handlobraesing]

bob gudgel
OutBack Power:

"...It's interesting how many things have trouble with modified sine wave inverters. Usually, they're more of a modified square wave but the industry has called them mod sine wave for years.

Some appliances like most microwave ovens rely on the higher peak voltage of a true sine wave and will not cook as fast on modified square waves.

Also, a lot of things expect the smooth slope of the sine wave so that their triac-light dimmer type circuitry will work properly. I think this is why some electric blankets will not work on mod square wave. They used to just turn on and off as I remember to regulate temperature.

Bread makers sometimes won't work. Some coreless drill chargers will break (De-Walt comes to mind) when plugged into mod-square wave sources.

Some RCA small dish receivers won't work. Square wave inverters make noise too lots of times... Audible acoustic and electric noise. Hi-Fi's and audio equipment can be noisey. Some computers will not work either although I haven't personally seen one that didn't.

Motors usually like sine waves better. Motors can run warmer on mod-square.

Usually the battery chargers built into mod-square inverters , if they have a charger built in, will normally be of the Triac light dimmer type and will have a low power factor and draw big current peaks, requiring larger than normal generators for battery charging as well as causing lots of electrical noise..."

also true sinewave IS more efficient than modified square wave, by about 20% -- google it and find a dozen confirmations.

Ok, for Wagan Tech brand 12v-120v inverter, I see 95% for sine, 90% for modified, although these inverters are setup very differently from UPS.
Small inverters like that uses a high-freq transformer to up the voltage, then form AC from the higher voltage DC.
UPSs makes AC 60Hz at low voltage side, then directly boosts it using a 60Hz iron core transformer. Open up a 300W UPS and you'll find a heavy iron core transformer. Open up a 300W portable inverter and you see a tiny ferrite core transformer.

That said, do you have efficiency figures for low frequency topology (that does not use multi-dozen KHz ferrite core transformer) inverters?

My computers + periphs are using 167.5W on power line, 162.3W when switched over to battery in UPS with modified squarewave inverter, so it looks like computer equipments are actually ~3% more efficient on modified squarewave. Measurement taken with externally connected power analyzer.

 

[TedTheLed]

oh nee tanzan wan, onee swatee mali wan.

I'd answer you if I knew what you were talking about.
Don't know if what you're saying makes any sense, but I'm afraid you'll have to simplify the question if you want to be understood, at least by myself..and I guess everyone else.


in the meantime here's from the Wagan site;

Q: Are there any disadvantages of using "Square Modified Sine Wave" inverter?
"Square Modified Sine Wave" inverters will run most tools and appliances without any problem and are the most common type of inverter on the market.
Below are the advantages of "Pure Sine Wave" (also called True Sine Wave) inverters over modified sine wave inverters:
1. Reduces audible and electrical noise in fans, audio amplifiers, TV and some sensitive audio system.
2. Inductive loads like microwave ovens and motors might run faster, quieter and cooler.
3. The following devices that might not work with modified sine wave inverters:
· Some battery chargers for cordless tools
· Some new furnaces and pellet stoves with microprocessor control
· Sensitive electrical or electronic items such as certain medical equipment

(Wagan is a Chinese manufacturer makes all kinds of (the least expensive) electrical devices on the market, like beaded car seat warmers, and personal fridges, and mostly mod-sine inverters, though they just came out with two new "Pure Sine Wave" models..)

 

[Handlobraesing]

oh nee tanzan wan, onee swatee mali wan.

I'd answer you if I knew what you were talking about.
Don't know if what you're saying makes any sense, but I'm afraid you'll have to simplify the question if you want to be understood, at least by myself..and I guess everyone else.


in the meantime here's from the Wagan site;

Q: Are there any disadvantages of using "Square Modified Sine Wave" inverter?
"Square Modified Sine Wave" inverters will run most tools and appliances without any problem and are the most common type of inverter on the market.
Below are the advantages of "Pure Sine Wave" (also called True Sine Wave) inverters over modified sine wave inverters:
1. Reduces audible and electrical noise in fans, audio amplifiers, TV and some sensitive audio system.
2. Inductive loads like microwave ovens and motors might run faster, quieter and cooler.
3. The following devices that might not work with modified sine wave inverters:
· Some battery chargers for cordless tools
· Some new furnaces and pellet stoves with microprocessor control
· Sensitive electrical or electronic items such as certain medical equipment

(Wagan is a Chinese manufacturer makes all kinds of (the least expensive) electrical devices on the market, like beaded car seat warmers, and personal fridges, and mostly mod-sine inverters, though they just came out with two new "Pure Sine Wave" models..)

The original poster wants to power his computer stuff, so basically motors, furnaces, medical equipment doesn't really affect his usage.

 

[Quickbeam]

FYI post...

I have a Belkin F6C800-UNV. Not the best brand, but it has voltage dip (brown-out) detection, so does not require a full outage to kick in. I have all my PC equipment plugged into it via two Belkin Surgemaster under-the-monitor type power strips with the switches on the front. Not the recommended way to use a UPS, I know - you're only supposed to plug applicances directly into the UPS. However it works great and I've never had a problem. Saved my bacon several times.

The batteries died and I had to order replacements from a third party - really inexpensive and work just great.

 

[TedTheLed]

<snip>
My computers + periphs are using 167.5W on power line, 162.3W when switched over to battery in UPS with modified squarewave inverter, so it looks like computer equipments are actually ~3% more efficient on modified squarewave. Measurement taken with externally connected power analyzer.

are you sure you unplugged the inverter before you took your measurement?
sounds like you're just measuring pass-through current from the wall socket.
what we want to know is the efficiency of msw vs. sw. -- not msw vs. wall outlet -- any way the measurement is irrelevant since it tells us what your equipment is drawing, not how much energy the inverter is drawing from the batteries to produce those watts..

sw is more efficient than msw.

 

[Handlobraesing]

are you sure you unplugged the inverter before you took your measurement?
sounds like you're just measuring pass-through current from the wall socket.
what we want to know is the efficiency of msw vs. sw. -- not msw vs. wall outlet -- any way the measurement is irrelevant since it tells us what your equipment is drawing, not how much energy the inverter is drawing from the batteries to produce those watts..

The WALL is sinewave.
When on inverter, the load is operated on modified squarewave and uses slightly less power.

sw is more efficient than msw.

Because why? Because you say so? First of all, your "more than 20% efficient claim" is busted even for the high-frequency switcher type. 95%/90% 1.06 =! 1.20. Not even close enough for government work.

Now, we are talking about UPSs, which uses 60Hz transformer and none of the high frequency steps. You know one is more efficient than the other because why? I know that no load current on stand-alone high-freq type inverter is quite low. sinewave The inverter on Smart-UPS 1400 takes 48W with zero load.

You also made a claim the sinewave type inverter has more surge capacity, this is because why? Supporting documents?

 

[TedTheLed]

now you are purposefully obfuscating. I meant sw from an inverter, not just sinewave from a wall socket. the wall socket isn't a sw inverter.

yes because I say so, and anyone reading this can go to any of a dozen alternative energy websites and look it up, which is why I'm not going to continue to debate it with you. I've been using sw and msw inverters for 15 years off grid, with a battery bank -- they both have readouts of amps consumed and produced..the sw uses less amps to produce the same watts.

if you are having a blackout you would, well maybe not you, but everyone else, appreciate having an inverter that could run everything normally run by wall socket AC -- like flourescent lights, another item msw can't run... want to charge your batteries? better not use a msw..

 

[Handlobraesing]

now you are purposefully obfuscating. I meant sw from an inverter, not just sinewave from a wall socket. the wall socket isn't a sw inverter.

yes because I say so, and anyone reading this can go to any of a dozen alternative energy websites and look it up, which is why I'm not going to continue to debate it with you. I've been using sw and msw inverters for 15 years off grid, with a battery bank -- they both have readouts of amps consumed and produced..the sw uses less amps to produce the same watts.

But you can't even tell me if they're low-frequency type or high-frequency type switcher? Small standby UPS is almost always the low frequency type. Dedicated inverter comes in either types.

Slippery slope.

if you are having a blackout you would, well maybe not you, but everyone else, appreciate having an inverter that could run everything normally run by wall socket AC -- like flourescent lights, another item msw can't run... want to charge your batteries? better not use a msw..

Chargers that use switching power supply on the front end, which is becoming the dominant type today works fine. DeWalt charger that uses a series L-C-R type circuit is one of the exceptions.

CFLs, fixtures with home-use rated electronic ballast works just fine as well on modified squarewave. Active PFC type ballasts don't always work well however.

 

[TedTheLed]

http://www.wholesalesolar.com/Information-Folder/inverters-article.html

"..The "modified sine wave" has detrimental effects on many electrical loads. It reduces the energy efficiency of motors and transformers by 10 to 20 percent. The wasted energy causes abnormal heat which reduces the reliability and longevity of motors and transformers and other devices, including some appliances and computers. The choppy waveform confuses some digital timing devices.

About 5 percent of household appliances simply won't work on modified sine wave power at all. A buzz will be heard from the speakers of nearly every audio device. An annoying buzz will also be emitted by some fluorescent lights, ceiling fans, and transformers. Some microwave ovens buzz or produce less heat. TVs and computers often show rolling lines on the screen. Surge protectors may overheat and should not be used.

Modified sine wave inverters were tolerated in the 1980s, but since then, true sine wave inverters have become more efficient and more affordable. Some people compromise by using a modified wave inverter to run their larger power tools or other occasional heavy loads, and a small sine wave inverter to run their smaller, more frequent, and more sensitive loads. Modified wave inverters in renewable energy systems have started fading into history..."

 

[Handlobraesing]

http://www.wholesalesolar.com/Information-Folder/inverters-article.html

"..The "modified sine wave" has detrimental effects on many electrical loads. It reduces the energy efficiency of motors and transformers by 10 to 20 percent. The wasted energy causes abnormal heat which reduces the reliability and longevity of motors and transformers and other devices, including some appliances and computers. The choppy waveform confuses some digital timing devices.

I just gave you the watt reading from my power analyzer comparing the power draw of the computer on sinewave(the wall) vs modified squarewave(UPS on battery). You didn't see the power consumption going up,did you?

My UPS does say "for use with computer loads only", but this isn't an issue for the original poster, who wants to backup his computer power.

 

[TedTheLed]

Originally Posted by TedTheLed
<snip> any way the measurement is irrelevant since it tells us what your equipment is drawing, not how much energy the inverter is drawing from the batteries to produce those watts..

...yawn..is this what threadlocks were invented for?

 

[Handlobraesing]

Originally Posted by TedTheLed
<snip> any way the measurement is irrelevant since it tells us what your equipment is drawing, not how much energy the inverter is drawing from the batteries to produce those watts..

...yawn..is this what threadlocks were invented for?

You don't seem to grasp the concept that if the computer's power supply becomes 10-20% less efficient, it would be using MORE power to operate.

when it's connected like this, the power measured is the power going to computer.
wall--UPS--power analyzer--computer

If the computer PSU becomes LESS efficient, it would draw more power from the power source.

 

[TedTheLed]

you're the one not grasping the concept;

you're right when you say--
"..when it's connected like this, the power measured is the power going to computer. wall--UPS--power analyzer--computer If the computer PSU becomes LESS efficient, it would draw more power from the power source..."

that's why your measurement of the power used by the computer is irrelevant; as you say above, you must measure the power drawn "from the power source" -- which would be the batteries..

 

[bfg9000]

I am not aware of any consumer power analyzer that is accurate with modified sine wave. The makers of the "Kill-a-Watt" even point out that while it will work with modified sine wave inverters, the readings may be off by 5-15%.

Measuring runtime to a certain voltage from the same batteries is the correct way to measure total efficiency here, because as we found in the Fenix Circuits thread, it's the end result in use that matters and not the conversion efficiency of any one component. Perhaps one particular UPS could get very inefficient at lower battery input voltages, for example!

Does it not strike you guys as grossly inefficient in the first place to convert 12v DC to 110v AC then back to regulated 12v and 5v DC to run a computer? If you wanted to run a PC long-term on batteries then just use a "carputer" power supply. I want something I can buy cheaply off-the-shelf that can automatically keep things running in minor power outages, so efficiency isn't a major selling point. Price, availability and reliability are far more important considerations for that, and the sine-wave adds flexibility for use with other items besides computers.

 

[Handlobraesing]

I am not aware of any consumer power analyzer that is accurate with modified sine wave. The makers of the "Kill-a-Watt" even point out that while it will work with modified sine wave inverters, the readings may be off by 5-15%.

I didn't use a Kill-A-Watt. Search Google for Valhalla Scientific 2101, the analyzer I used.

 

[TedTheLed]

".. Under (low load) conditions, an inverter's efficiency may be around 50 percent or less. The full story is told by a graph of efficiency vs. load, as published by the inverter manufacturer. This is called the "efficiency curve." Read these curves carefully. Some manufacturers cheat by starting the curve at 100 watts or so, not at zero!

Because the efficiency varies with load, don't assume that an inverter with 93 percent peak efficiency is better than one with 85 percent peak efficiency. If the 85 percent efficient unit is more efficient at low power levels, it may waste less energy .." -- Windy Dankoff