APC-UPS sq wave to sine wave

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ryker

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Have two apc ups, that produce a square sine wave. If possible, and of course feasible, would an electronics shop be able to redo what it would take to get them to put out more of a pure sine wave. I want to use these as backups on two different 110ac motors, and the square wave that they produce now really does a bad job at running them.

As I said, I realize that it may not be worth the money vs. just buying a sine wave apc, but I hate not be able to use these two I have.

Thanks
 

catchtwentytwo

Senior Member
ryker said:
Have two apc ups, that produce a square sine wave. If possible, and of course feasible, would an electronics shop be able to redo what it would take to get them to put out more of a pure sine wave. I want to use these as backups on two different 110ac motors, and the square wave that they produce now really does a bad job at running them.

As I said, I realize that it may not be worth the money vs. just buying a sine wave apc, but I hate not be able to use these two I have.

Thanks

What size and type motors? It sounds like you are using a "commodity type" UPS. I suspect you'll have a problem finding smaller UPS's (square or sine wave) that can handle the starting inrush but only the manufacturer could advise you on that.

I really doubt any shop could modify them at a reasonable price. It is unlikely that APC would provide internal schematics on a board level so you'd pay for reverse-engineering, assuming anyone would take on the task.
 

ryker

Member
reply-long

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Live in Wa.state-have honda gen for stand-by power. Big house with two pellet stoves. Every year (wind strorms) and trees out in the country, we go down without power. The pellet stoves don't draw like reg.stove, and smoke up the house when the power goes out, burning the pellets still in the hopper. Want to use the ups to power the fans on the stove until pellets are used up (fan exhausting smoke) when power goes down, to stop the smoke in the house and allow me to shut off the stove, and then reignite under the backup gen.

I have a sine wave apc-ups, that does do this, (fans in the stove are variable speed fans-and draw only about 1.5 amps when running), but this apc is dedicated to the computer system. The problem with the square wave apc, is that the stove-fans-auger, all work off a controller board, and when the power goes down, and the sq-wave apc kicks in, because of the sq-wave, the fans run slow, but worse yet, the control board makes a real bad hum, it really does not like it. If I blow the board, there's about $250 for a new one. The apc sine wave for the computer does not produce this affect, it works well.

That's the reason I wanted to see if I could get a more or better sine wave out of them. I don't want to replace the board, if I kill it.
 

tallgirl

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Location
Great White North
Occupation
Controls Systems firmware engineer
coulter said:
dereck -

Just thinking without a pencil --

1:1 xfmr, square wave in, triangle wave out?

carl

Depends on how sharp the square wave is. It could get really ugly depending on the shape of the input wave.

But, yeah, square wave in isn't going to get a sine wave out.
 
If you ram a square wave through a big enough 60Hz low pass filter, you'll get a sine wave. OTOH it'll be cheaper to get a UPS that outputs a sine wave in the first place. The APC SmartUPS series does have a sine output, the BackUPS has a stepped square wave (when I checked a couple of years ago).
 
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