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Author Topic: Generator power - Why square waves are bad, and other things to look out for.  (Read 10982 times)

Scott Wagner

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Based upon your description of the genset, it's not a "construction" genny.  You'll be fine.  Bring your metering equipment to verify (as you should always do).
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Scott Wagner
Big Nickel Audio

Mike Sokol

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Unfortunately, no B3s at this gig.

Too bad... I've been teaching sound mixing seminars at a bunch of Southern Baptist Churches lately, and many of them have a Hammond B3 and a pair of 122 Leslie speakers. I'm thrilled to hear one with a great player.

I myself am a B3 player and still have my 1954 model B2 which I converted to a B3 using Hammond factory parts back in the 70's. And it's still on its original tubes from 1954. Talk about solid engineering..

Back OT...
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Tom Bourke

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Even a Honda inverter-generator (suitcase type) makes a modified square wave output, but it looks very much like a sine wave on a scope and should never cause a problem.
My understanding was the Honda i and EU series were VERY clean sine wave.  I have even heard  ham radio operators claiming they were better than what comes out of your wall!
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g'bye, Dick Rees

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My understanding was the Honda i and EU series were VERY clean sine wave.  I have even heard  ham radio operators claiming they were better than what comes out of your wall!

Here are a couple shots of a 'scope trace on my Honda EU2000i, the first at idle, the second under a static load (1KW work light).

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Mike Sokol

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My understanding was the Honda i and EU series were VERY clean sine wave.  I have even heard  ham radio operators claiming they were better than what comes out of your wall!
I've read a lot of forums where they claim the Honda generators make a "pure" sine wave. But in the interest of accuracy, I think that while for all practical purposes they make a pretty darn good sine wave, they still have a few percent of THD. As seen on the scope they "look" like a "pure" sine wave, but it would be interesting to run a FFT on the waveform under various loads. I really don't think they're "cleaner" than power company AC from synchronized generators (excepting for transient junk, of course).

I've seen a few scope traces of "lesser" inverter-generators from cheap import manufacturers, and they really look like stepped sine wave outputs. Not pretty and with tons of harmonics. Still better than the cheap square wave inverters, but not as good as a Honda output which appears to be the gold standard of consumer inverter-generators.
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g'bye, Dick Rees

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I've read a lot of forums where they claim the Honda generators make a "pure" sine wave. But in the interest of accuracy, I think that while for all practical purposes they make a pretty darn good sine wave, they still have a few percent of THD. As seen on the scope they "look" like a "pure" sine wave, but it would be interesting to run a FFT on the waveform under various loads. I really don't think they're "cleaner" than power company AC from synchronized generators (excepting for transient junk, of course).

I've seen a few scope traces of "lesser" inverter-generators from cheap import manufacturers, and they really look like stepped sine wave outputs. Not pretty and with tons of harmonics. Still better than the cheap square wave inverters, but not as good as a Honda output which appears to be the gold standard of consumer inverter-generators.

I'll look for my notes.  We did take some THD readings and IIRC, they were comparable or cleaner than the house power from the grid.
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John Roberts {JR}

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I'll look for my notes.  We did take some THD readings and IIRC, they were comparable or cleaner than the house power from the grid.

As long as the waveform is not so distorted that the top is flattened and delivering inadequate voltage when rectified, the purity is not a significant concern.

JR

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g'bye, Dick Rees

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As long as the waveform is not so distorted that the top is flattened and delivering inadequate voltage when rectified, the purity is not a significant concern.

JR

A spouse mandated "house-cleaning" has apparently displaced my notepad from the tests.  IIRC, THD was more remarkable for being low than anything else.  I believe I was given the right to gloat about the power from the Honda.

I will not throw out a number until I can find the notes or see if the others present recall the range of THD.  All I remember is that it produced grins all around.
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John Roberts {JR}

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A transformer is a bandpass device so extreme purity of the waveform is not a concern. If I was selling Honda generators I might hype that, but don't be confused into thinking this matters in the margin, only when distortion is extreme. 

JR

PS: I am  surely repeating myself by now so see ya later...  8)
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g'bye, Dick Rees

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A transformer is a bandpass device so extreme purity of the waveform is not a concern. If I was selling Honda generators I might hype that, but don't be confused into thinking this matters in the margin, only when distortion is extreme. 

JR

PS: I am  surely repeating myself by now so see ya later...  8)

OK.  Just for s***s and giggles, here's a shot of the trace of an APC UPS, $165 from Office Max.  Two different resolutions...
« Last Edit: November 18, 2013, 01:06:32 pm by dick rees »
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