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Old 06-11-2015, 11:16 AM   #11
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OK...I'll ask. Other than big, brown trucks...what are "UPS's"?
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Old 06-11-2015, 11:26 AM   #12
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The explanation disappears down a rat-hole of electrical theory pretty fast.. The "pure sine" power is just that, a single sine wave at 60 Hz frequency. The "modified sine" aka multi-level square wave is equivalent to the sum of a great many sine waves at various frequencies (see Fourier Series). The biggest component is still a 60 Hz sine, but there are many others too. It's the presence of all those other frequencies that can cause trouble because the device may respond to each of those frequencies in different ways. For the most part devices will deal with this, definitely some better than others. For example it's common for devices to run hotter than they normally would when powered with MSW. Also motors may make more noise when fed MSW.
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Old 06-11-2015, 12:16 PM   #13
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The explanation disappears down a rat-hole of electrical theory pretty fast..
Even I had questionable looks on my face in the Electronics Principles section of the Air Force's 3D1 (Cyber Systems Support) tech school

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OK...I'll ask. Other than big, brown trucks...what are "UPS's"?
Uninterruptible Power Supply. They're supposed to provide enough power to save and shut stuff down in the event of commercial power issues.
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Old 06-11-2015, 02:15 PM   #14
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just finished having lunch with my buddy, the electrical engineer. When asked about the good vs. bad, and why, he seemed to think it was hype. When asked what types of appliances or electronics might be negatively affected, he shrugged and said, "MAYBE LEDs"?

Beginning to think this is simply a sales tactic from the inverter industry? As in, "this is much better, that is why it costs more, and if you don't buy this, you will ruin everything you plug into it"
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Old 06-11-2015, 04:06 PM   #15
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The Wynns (who fulltime in a commercial RV) weigh in-
Best Inverter for an RV – Pure vs Modified and Watts
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Old 06-11-2015, 04:40 PM   #16
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The Wynns (who fulltime in a commercial RV) weigh in-
]

ahh yes.... The Shills, uh, I mean The Winns, well at least they acknowledge the sponsorship


I love The Winns, but they provide essentially the same remarks - buy it cuz it is betterer. The only interesting thing they said was "some items will not run on MSW" - and I would like to know what those items are?

Also, what items would be damaged? Of course it would be the expensive kind, otherwise, how could you justify the added costs?

Mr. Shill even says at the beginning of the video "without putting you to sleep with some super-technical nerd-out session...." and then continues by showing more standard waveform graphics, avoiding ANY real info....

But I still want the nerd out session.
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Old 06-11-2015, 05:46 PM   #17
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I think "harmonic distortion" is name of the phenomenon of interest. Also known as "total harmonic distortion" or THD. Here are two articles on that topic: http://www.aptsources.com/resources/...Distortion.pdf Effects of Harmonics on Power Systems | Power Quality content from Electrical Construction & Maintenance (EC&M) Magazine

The first is from a company who sells power sources. They appear to be useful for test lab or other industrial applications. The other is directed to plant managers and other commercial/industrial maintenance type people. These are written from the perspective that some kinds of loads introduce distortion back into the mains that feed them, and also into other equipment connected to the mains. I think it's appropriate to consider the modified sine inverter to be a power source with high THD. Those articles explain how high THD can negatively affect some kinds of equipment.

While searching that out I ran across a reminder that some battery chargers specifically indicate they should not be operated on a MSW supply, and Reports On The Internet (those are always reliable, right??) suggest some tool battery chargers run on MSW may ruin the batteries and/or the charger. In particular, those which are marked "hazardous voltages may be present at the charger terminals" -- but I STILL haven't found any explanation as to WHY this type doesn't play nice with MSW. That's annoying me. This post on candlepowerforums gets close, but from reading just that thread I can't determine to what degree that author might/might not be an expert and in any case there isn't a great level of detail given in the theory.

Power Stream has an interesting inverter FAQ on their site Inverter frequently asked questions.
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Old 06-11-2015, 10:48 PM   #18
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ding ding ding, we have a winner

3 for 3 articles, and now I think I may understand the importance of "clean power" (still reading, the 3rd time now )

thanks family wagon
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Old 06-12-2015, 12:40 AM   #19
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That is almost always the case with power electronics. The number and size of transistors or similar devices, the connecting wires, etc all affect how much current the electronics can pass. By "right sizing" the electronics, manufacturers can keep costs down, and market share or profits up.
Good to know. Thank you for your help!

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Be aware that many if not most UPSes put out modified sine wave which is quite unkind to motors such as your fans and chest freezer. Further, cheaper UPSes will literally cook themselves at duty cycles outside of their original range.
I did think about the modified sine wave issue. I see that some UPS units and inverters have true sine wave. They are usually exponentially more expensive. I did not consider the duty cycle.

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I always understood it as anything other than pure sine wave is dirty electricity and it will prematurely age some devices, some devices won't even start.
UPS's are designed to sit virtually unused for years so if you start using one constantly it may not last long, same concept as "duty cycle" mentioned above
Thank you for your insight. I wonder how much they would last as compared to their usual lifespan.
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Old 06-12-2015, 02:12 AM   #20
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I run my 20 volt Dewalt tool battery chargers off MSW inverters in the truck all winter. No issues so far.

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