UPS with the best (purest) sine wave output

I need a UPS with pure sine wave output. When the specification says "pure sine wave" or "sine wave" (I've noticed e.g. APC uses word "pure" nowhere), does it mean the output is pure sine wave comparable with the utility power?

Or is the "pure sine wave" only a better approximation of a stepped sine wave? In that case what is the cheapest UPS with the best sine wave available?

thanx

I work with ups's daily

Here you can see that there 'Pure' sine wave ups's aren't called it pure \/
http://www.apcc.com/resource/inclu [...] ku=SUA1500 - I love these, banks use them all around the world
http://www.apc.com/resource/includ [...] UA1000RM2U


Here you can clearly see that this isn't pure, it's Stepped approximation to a sinewave \/
http://www.apc.com/resource/includ [...] sku=BE550R
http://www.apc.com/resource/includ [...] _sku=BK350

Matter of fact, they don't even state 'pure' on their $10-20k ups's. If you have a problem with their style of naming, you can email them a complaint. Pure isn't a word manufactures have to use, some use it, some don't. In reality, there's no such thing as a trully pure sine wave ups. Find your nearest Electrical Engineering company or school and they'll be glad to explain this to you.
http://www.apc.com/resource/includ [...] watts=4000
http://www.apc.com/resource/includ [...] watts=2000

You don't necessarily need the best sine wave for general home pc's.

http://www.amazon.com/APC-SUA1500- [...] B00006BBK8
Get this one and be done with it.

'Pure' sine wave, almost 40 amps (this means "at-least" 1.5 hours of power for one pc), 950+ watts and easy maintenance.




Email APC for any further questions you have, your the costumer and it's your money.
GPU.

what? can you elaborate or post a link to some articles that address this issue? Does it mean that every UPS I eventually buy will stress the connected equipments when running on battery?

I do. As I just wrote one post above I need prolonged time running on battery without overly stressing the connected equipments...

I did (actually the same time as I was setting up this thread). But I need some independent opinions because the sellers will never tell you everything (even if they are ultra-fair to their customers they still have an insider view which causes distorted perception).

That's why I need some independent opinions and I thank to everyone who gives me some!

I'll try to make a quick comment here. Most UPS's use cheap and easy methods to provide 120VAC outputs. They switch abruptly for each cycle using components like SCR's or High Current Darlingtons - but they have minimal filtering to keep the expense and complexity down. The output is more of a square wave than a smooth sine wave. If you're familiar with some of the engineering, it's 60 Hz +/- a lot of other frequencies that you don't need.

When used with older equipment with transformer power supplies - including computers (they have pretty decent filtering) - no harm is done. The non-60 Hz frequencies are either rectified into DC with a little more noise or filtered.

But these UPS's pose a danger to newer solid state equipment. Solid State power supplies use SCR's to produce DC from AC. They are designed for sine wave power, using a specific voltage level to trigger a particular side of the DC conversion. (on the positive and negative swings). When the SCR is on, it is conducting full current. When they are using norman sine waves, it is turned on for only a small portion of each cycle.

But when the power is a square wave, the voltage threshold is reached almost immediately per cycle. This causes the SCR to be turned on for about 90% of the time. The components will overheat and burn out if not protected. This means a dead power supply in that brand new $4,000 LED TV. If I pull the plug on mine, I can hear the TV power supply switching violently (it makes a rather audible 'eeeeeeeeeeeeeeeeeee' sound. That's not good for more than a few minutes - the SCR's will overheat and die.

Be VERY careful when using cheap UPS's on new televisions. They work well to prevent damaging undervoltage or long time variant spikes due to power line disconnects (or lightning triggered interrrupts), but they are NOT to be used long term. If you have the money, buy a "pure sine wave" product. It will be more expensive and bigger due to the filtering and regulation components, and a bit less efficient, but it will provide power to your equipment in a form it was designed for.