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What is the difference between normal and pure sine wave inverter+ups?

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June 19, 2010 6:32:36 PM

Hi
I want to buy a ups cum inverter for the home and pc as well bacause of very frequent power cuts in summers .then in shop ,I came across two types-
(1)the normal ups cum inverter(cheap)
(2)pure sine wave ups cum inverter(expensive).

so what to choose?will the normal ups cum inverter affect my home appliance and pc parts?
Also is it OK to have a UPS cum Inverter or shall i go for a UPS separately?
some says that the ups cum inverter is again harmful to pc components.
a c 274 ) Power supply
June 19, 2010 6:53:57 PM

I went with a cheaper simulated sine-wave ups and i'm not too concerned.
For the amount of power interrupts in my neck of the woods and the fact that i don't run my rig 24/7.
It's much better protection then nothing and a huge upgrade from what most people plug their gear into.
When the ups is activated you'll hear a buzzing noise which is emitting from your psu.A high quality psu can take this no problem as long as it's not a frequent event.
For the half a dozen times a year it happens to me i'm not concerned plus i've been sitting there 90% of the times it happend.
Yes a pure sine-wave unit is superior and won't effect the psu(buzzing).
and a must have for 24/7 operation and mission critical set-ups neither of which effect the normal user.
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a c 271 ) Power supply
June 19, 2010 7:53:17 PM


Most inverters output a stepped square wave(red line), its easier to design a circuit to output this thus they are cheaper and more commonly used, a pure sine wave(black line) is what is provided by the power company. PSUs are not designed to take this signal in so you get some buzzing and depending on the quality of the PSU and the filtering in it it could shorten the lifespan of the PSU, however the components in the system itself will be fine as the PSU shields them.
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a b ) Power supply
June 20, 2010 2:08:21 AM

For feeding power to a computer PSU, a "normal" UPS might be OK. It depends both on how many steps the simulated sine wave has -see the difference between the blue and red lines in hunter315's post - and on how good the PSU is. But there are other devices here. What about your monitor? Your router? Your cable modem (or ADSL modem)? Your speaker system? Your printer? OK, maybe not the printer - many people do NOT try to keep a printer going when the power fails. ALL of those are going to be receiving the power, and you really have no control over the quality of the power supply circuits in each of them. But maybe, as Davcon says, for a few times per uear the risk is not much to worry about.

On the other hand, anything with motors is more worth worrying about. AC motors that run from the input supply directly (unlike computer fan motors that run from the PSU's DC outputs) can have a lot of trouble with power supplies that are not reasonably smooth sine waves. Now, maybe you don't plan to run any such devices off the UPS. After all, most items with even moderate AC motors in them can use up all the backup power stored in a UPS rather quickly. Just remember that as you plan your system.
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June 20, 2010 2:26:22 AM

ok.so if i go for a normal ups all i have just is buzzing the psu.and no harms to my psu and other devices.I have cooler master ucp 900w,and rest config is normal including a radeon 4870 gfx card.
though i will be running fans and lights on this ups cum inverter in my room,but the the thing i am more conscious about is my PC components security..
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June 20, 2010 2:30:45 AM

hunter315 said:
http://www.screenlightandgrip.com/images/generators/Inverter_Wave_Comp.jpeg
Most inverters output a stepped square wave(red line), its easier to design a circuit to output this thus they are cheaper and more commonly used, a pure sine wave(black line) is what is provided by the power company. PSUs are not designed to take this signal in so you get some buzzing and depending on the quality of the PSU and the filtering in it it could shorten the lifespan of the PSU, however the components in the system itself will be fine as the PSU shields them.

i will not be running the PC on inverter/UPS for a large time.all i need is just time needed to save my work and shut down the pc.though i might run my pc (in case of emergency)for some more time.So will it still affect my psu's life span?i am having cooler master ucp 900w psu.
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August 8, 2010 11:05:04 PM

The biggest issue will be your monitor. If you have a middle- to high-end monitor, or a LCD monitor, a stepped waveform could cause it serious damage. If you want a UPS to save your work when the power blinks out, then you'll need your monitor to stay on as well. If your UPS damages your monitor when it kicks in, not only are you unlikely to be able to save your work, but your stuck covering the loss of the monitor as well, and neither the UPS or monitor warranty covers this.

I know this from personal experience. My 850-watt 750vamps online simulated sine wave UPS blew out the backlight of my LCD monitor, causing damage to the screen as well. I replaced that UPS with one that is a 500-watt 750vamps line interactive (often called AVR) with pure sine wave output. The new UPS was about $90 more expensive than the old one at $320, but it has served me well. Incidentally, replacing the monitor cost me around $110. I should have simply spent a little more buying a UPS with a true sine output in the first place.

I don't know what the lowest cost pure sine wave UPS would be, but you might be able to find one for under $150. You just have to look.
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August 19, 2010 3:05:28 AM

Best answer selected by darksmart.
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