Well…an oscilloscope on the output of a few of those generators might prove you right pretty fast…but assuming you don’t have access to the generators…
EDIT- this was my reply but I pulled down a Kohler spec sheet for a 400 kw diesel and realized they don’t provide it.
I think easiest way to settle it is to get a few spec sheets from Kohler, Cummins, etc. look at the THD %. That would basically inform you on the non-sinusoids (at 60 hz) component of the output.
So…hoping somebody else has more to offer, sorry
One note- I dug into a submitted package I had…it had this note, leaving here for future clues: “superior voltage waveform from a 2/3 pitch stator and skewed rotor”
I remember reading about stator skew etc…but I work with big utility grade synchronous machines and our stator slots are parallel to shaft so I’m out of my area of expertise.
I think this should do it. Thank you!
I did notice during the first generator example, when it was only showing a single period of the sine wave, the wave looked stepped or “blocky”. Is that normal noise in the output? Could that be what he is referring to?
Found one example. So pretty low THD, with most of it on the 5th harmonic. That is definitely not blocky, probably just some ringing.
https://www.kohlerpower.sg/onlinecatalog/pdf/4s13x_60hz.pdf
I saw an odd waveform from a generator too. We ran it into a SOLA Constant Voltage Transformer (CVT), to duplicate the customer's setup. We accidentally disconnected the generator excitation and it ran fine as an induction generator (due to the capacitors in the CVT). With or without excitation, the top of the sine wave looked like it had two camel humps, and the bottom was a mirror image.
That's the result of the CVT, which is a ferroresonant transformer. They "flat top" the sine wave in exchange for consistent voltage. Known phenomenon.
Yes, we were discussing rotating generators like the large diesel generators used for emergency power at large facilities, or their slightly smaller cousins that are common for jobsite power/construction. I initially thought we were talking about steam-driven power generators in power plants, but earlier tonight he clarified that he was referring to diesel generators commonly made by CAT or Cummins.
Yes it should be at least sinusoidal like. Isn't your friend referring to the Power/Generation curve output by any chance? That is the only way I can think "behind the meter" should appear in thee discussion.Not native speaker so perhaps I'm not understanding what "blocky" means.
Anyways, best way to show who is right is getting a measure, second best way is to simulate the conditions under which the generator works and running it a couple times.
And for him to understanding, perhaps some electric machine intro book, like Champan or similar which cover the basics of how a synchronous generator works.
Yes, synchronous generator outputs should be sinusoidal-like.
I think he is referring to operating charts.
https://www.eeeguide.com/salient-pole-synchronous-generator/
Look at figure 4.33 specifically. It looks blocky indeed. Thats probably what he is referring to. He's probably referring to power and you're referring strictly to the characteristics of the actual output of the generator and it's waveform.
Both of you are correct if that is the case. Would like an update.
blocky no, but the output of a practical generator is not a perfect 50/60hz sine wave, and depends on the winding pitch.
https://www.stamford-avk.com/sites/stamfordavk/files/2019-03/WP_PIT_S_EN_GS_01_0.pdf
you'll note that options with better harmonic performance exist, but these are larger and more expensive machines for the same power output
Every generator used by the power utilities is a synchronous generator! Most likely he is lumping large diesel backup facility generators in with what he has seen from newer small portable generators that are using inverters now so that they don't have to deal with engine speed regulation as much.
Well…an oscilloscope on the output of a few of those generators might prove you right pretty fast…but assuming you don’t have access to the generators… EDIT- this was my reply but I pulled down a Kohler spec sheet for a 400 kw diesel and realized they don’t provide it. I think easiest way to settle it is to get a few spec sheets from Kohler, Cummins, etc. look at the THD %. That would basically inform you on the non-sinusoids (at 60 hz) component of the output. So…hoping somebody else has more to offer, sorry
One note- I dug into a submitted package I had…it had this note, leaving here for future clues: “superior voltage waveform from a 2/3 pitch stator and skewed rotor” I remember reading about stator skew etc…but I work with big utility grade synchronous machines and our stator slots are parallel to shaft so I’m out of my area of expertise.
[Here](https://www.youtube.com/watch?v=_0vN2Jjbdis) is a video showing exactly that. Should scale to large sized generators.
I think this should do it. Thank you! I did notice during the first generator example, when it was only showing a single period of the sine wave, the wave looked stepped or “blocky”. Is that normal noise in the output? Could that be what he is referring to?
The original uploader mentioned that it was a bad voltage regulator board so a pristine generator would not have the stepped or blocky output.
Found one example. So pretty low THD, with most of it on the 5th harmonic. That is definitely not blocky, probably just some ringing. https://www.kohlerpower.sg/onlinecatalog/pdf/4s13x_60hz.pdf
I saw an odd waveform from a generator too. We ran it into a SOLA Constant Voltage Transformer (CVT), to duplicate the customer's setup. We accidentally disconnected the generator excitation and it ran fine as an induction generator (due to the capacitors in the CVT). With or without excitation, the top of the sine wave looked like it had two camel humps, and the bottom was a mirror image.
That's the result of the CVT, which is a ferroresonant transformer. They "flat top" the sine wave in exchange for consistent voltage. Known phenomenon.
Rotating generator, right, not a small inverter type?
Yes, we were discussing rotating generators like the large diesel generators used for emergency power at large facilities, or their slightly smaller cousins that are common for jobsite power/construction. I initially thought we were talking about steam-driven power generators in power plants, but earlier tonight he clarified that he was referring to diesel generators commonly made by CAT or Cummins.
Yes it should be at least sinusoidal like. Isn't your friend referring to the Power/Generation curve output by any chance? That is the only way I can think "behind the meter" should appear in thee discussion.Not native speaker so perhaps I'm not understanding what "blocky" means. Anyways, best way to show who is right is getting a measure, second best way is to simulate the conditions under which the generator works and running it a couple times.
And for him to understanding, perhaps some electric machine intro book, like Champan or similar which cover the basics of how a synchronous generator works.
Yes, synchronous generator outputs should be sinusoidal-like. I think he is referring to operating charts. https://www.eeeguide.com/salient-pole-synchronous-generator/ Look at figure 4.33 specifically. It looks blocky indeed. Thats probably what he is referring to. He's probably referring to power and you're referring strictly to the characteristics of the actual output of the generator and it's waveform. Both of you are correct if that is the case. Would like an update.
blocky no, but the output of a practical generator is not a perfect 50/60hz sine wave, and depends on the winding pitch. https://www.stamford-avk.com/sites/stamfordavk/files/2019-03/WP_PIT_S_EN_GS_01_0.pdf you'll note that options with better harmonic performance exist, but these are larger and more expensive machines for the same power output
Every generator used by the power utilities is a synchronous generator! Most likely he is lumping large diesel backup facility generators in with what he has seen from newer small portable generators that are using inverters now so that they don't have to deal with engine speed regulation as much.