Pictures of "dirty" backup power...

[Besoeker]

Maybe I'm missing something. I understand why devices wouldn't want spikes and dips in the power, but I don't understand why any device would have a problem with a nice square wave (providing the equivalent rms was attenuated ). Perhaps someone can enlighten me ?

If the supply is feeding something where it is first rectified, then yes, I suppose a square wave could work.
Some phase-controlled devices, conventional dimmers for example, calculate conduction angle by comparing a DC voltage with a sine wave or cosine wave synchronised and phase related to the supply. If the supply was a square wave, you would have all or nothing.

 

[Billy_Bob]

A couple of google searches will find plenty of problems with furnaces and back-up power - either inverters or generators. Here are a couple of searches...

furnace not working generator
http://www.google.com/search?hl=en&q=furnace+not+working+generator&btnG=Google+Search&aq=f&oq=

furnace "not working" inverter
http://www.google.com/search?num=20&hl=en&safe=off&q=furnace+"not+working"+inverter+&btnG=Search

Then general inverter problems...

"not working" inverter
http://www.google.com/search?num=20&hl=en&safe=off&q="not+working"+inverter&btnG=Search

inverter drill burned sine
http://www.google.com/search?num=20&hl=en&safe=off&q=inverter+drill+burned+sine&btnG=Search

 

[SEO]

SEO,
Your clock may have been determining how long one second is but watching input power sine wave peaks. If the power quality is bad, the clock may have gotten confused because it detected lots of peaks, rather than 60 positives per second.

Why wouldn't the utility power correct the clock and the inverter did?

 

[Rampage_Rick]

I've seen many double corded servers that have one supply as Phase A and the other supply Phase B, and they work fine normally and during failover conditions. Now that is not a square wave, but that is two inputs that are out of phase and still the output to the server is fine.

Two power cords would likely indicate redundant power supplies. Each power supply operates independently and outputs various levels of DC to the common rails. In theory, one could supply one cord at 120V and the other at 240V (assuming that's within spec) and the system would see that as "normal". In a properly designed system, there shouldn't be any coupling between the AC inputs.

Simplified: (There would 5 or more DC busses of different voltages)

120VAC --> Power supply --> 12VDC bus <-- Power supply <-- 240VAC

Continuing this assumption, the server should balance the DC load among the power supplies, and as a result you'd have roughly similar wattages on each circuit. Computer couldn't care what the incoming AC looks like so long as it's within spec and both power supplies are operational. One goes out of spec and the entire load is transferred to the good one.

 

[ron]

Rick,

Computer couldn't care what the incoming AC looks like so long as it's within spec and both power supplies are operational.

Thanks for expanding. Your statement was my point.

 

[tom baker]

I have had this exact discussion before, and could NOT find ANY evidence that the "modified" sine wave output had ANY ill effects even on high-end electronics.

If ANYONE can put forth any information debating that, I would love to see it.

We see it with certain generators that we try to run our traffic signals on in an outage.
Some work, some don;t, IE cause the traffic signal conflict monitor to trip out and put the signal in flash.

Is the power supply that determines how the equipment will work or not with odd sin waves.

 

[brian john]

I never cared for the term "Dirty Power" all to encompassing? Not sure but if power can be dirty these may fall in that category?

Voltage is the black current is red.

 

[weressl]

The first picture at the following link shows what a true or pure sine wave should look like (60 Hz), then the following pictures show the sine waves from various UPS, generators, and inverters. (Not very good in some cases.)

http://www.jkovach.net/projects/powerquality/

You get what you pay for.

Although small UPS's function well on individual PC's it is a stress on the power supply as they are designed for ideal sine wave, the PC will be obsolete before the power suply goes.

Three phase large UPS's have large filtering networks that synthetize a much more pefect sinewave.