[LinuxUsers] Sine wave vs shaped square wave

[Jeff Lasman]

On Wednesday 03 June 2009 06:32 pm, David Kaiser wrote:

> You're saying there is an option to not using sine wave?  Aren't sine
> waves the crux of alternating current?   I have no idea if there is
> any usable products or devices that work against square wave power -
> do you have some firsthand knowledge of this?

Why of course <smile>.  The most interesting answer is in the link at 
the bottom of this post, but ...

All consumer-grade UPS products I know of are stepped square wave; an 
example is here:

http://www.samsclub.com/shopping/navigate.do?dest=5&item=362641

Why they don't say anything about it on the page above, you can read 
about it here:

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BN1250LCD

Notice they say:

<snip>
Stepped approximation to a sinewave
</snip>

Which is what I call a "stepped square wave".

> Are these square-wave products cheaper or something?

Much cheaper.  The 1250VA unit I linked to above costs $129.68 at Sams 
Club.

A Similar 1500VA Smart-UPS (true sine-wave) here:

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SUA1500&total_watts=50

(I couldn't find a 1250VA comparable Sine-wave unit; perhaps I didn't 
look carefully enough)

... costs $560 plus shipping (and they're heavy; this one has a shipping 
weight of 60 pounds).

> For those of us that are not data-center junkies, can you provide us 
some additional information?

I just now found this:

http://www.kerchner.com/electrical/sinewave.htm

and though written in '85, it appears to be something I can trust today.

So the answer is I can certainly go ahead and get a cheap(er) stepped 
square wave UPS.

I hope this has been as instructive for those of you who've read and 
replied as it has been to me.

So I'm going to look through my store-room tomorrow to see if I have 
another UPS I can run if we continue to get thunderstorms and power 
outages.  Otherwise to Frys to see what they've got to compare with 
Sams Club.

Thanks for the input; the research to reply helped me find the answer.

<smile>

Jeff
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