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How dirty is your generators electricity? Most people haven’t a clue. Others see their voltage and frequency to be on point and assume their generator is great. The truth is not all generators produce clean power, and the ones that advertise super low THD might not be up to snuff.

I have scope readings I’ve taken on various generators. Enjoy

THD = Total Harmonic Distortion


GRID/UTILITY POWER








Honda Eu7000is Advertised at less then 3% THD. Loaded or unloaded it’s the same..... perfect. I think it’s actually cleaner then my grid reading.








Honda EB6500x No advertised THD


No load






4600watts load









Kohler 20Kw standby generator. Advertised at less then 5%THD

Under approx 1/4 load.



 

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PowerMate PM0126000 No Load



PowerMate PM0126000 Half Load
 
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yup the honda eu7000is wave looks like the ones we have as well.

pretty lumpy on the rest of the waveforms lol...

the time factor lumps hummm.

I wonder what fq's on the spurs are all in there on the lumpy wave forms??

an inverter gen is like a motor drive so everything "sings"
listen to a honda gen when it shuts down.
you can hear the pulse!!

I was able to get them to change out the pole transformer here 10 years back..
it was horrible on the sag and time..
they put in a data logger for a week to record the waveform
and did another a couple of houses down from me on a different pig.

they did a good job finding the issue.
the new pig so far has done well

the old pig was super noisy when you used an am radio by it.
arc inside the pig some where.
 

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Ah, nice posting, drmerdp, especially for folks not able to visualize what a distorted waveform looks like.

The surprising truth, if you'll allow me to steal the phrase, is most electrical equipment will tolerate a horrible looking sine wave. For quite a while, too.
I know what you're thinking, 'long term stress & unpredictable point failure'. And you'd be right. Still, over / under voltage is more dangerous for quickly taking something out, overvoltage being the major villain. And frequency, of course, will cause strange effects.

By the way, @tabora, I sold my Dranitz gear on eBay when I retired. Sweet stuff! I sure wish I kept it; it was the best monitoring & recording! Better than anything Fluke, on par with Tektronics. Can I borrow it and maybe promise to give it back? <GRIN>
 

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I am being re-educated!
I used large oscilloscopes mounted on a push cart when I was a technician in industry.
A friend of mine was a TV repairman and he had two scopes.
A few years ago he asked me if I wanted one of the scopes.
I declined his offer.
At the time I had no need for one as being retired I did not need it.
He sold the entire tube inventory, the scopes and meters to a guy in South Carolina.
Now, I realize that I should have taken him up on his offer.
I am considering buying a scope just to satisfy my curiosity after reading the above post.
My curiosity is running rampant!
 

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@toolover, one of my fluke meters is the 867b, a dvom with 1mhz oscope function. It's OK, not particularly fast but the lcd display is nice, it has auto adjust, is quite good enough for 60hz sine.
I paid $1k new, year 1998, you can now get them used for low 200's, maybe less.
Just one option for you if you also need a multimeter.
 

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@toolover, one of my fluke meters is the 867b, a dvom with 1mhz oscope function. It's OK, not particularly fast but the lcd display is nice, it has auto adjust, is quite good enough for 60hz sine.
I paid $1 k new, year 1998, you can now get them used for low 200's, maybe less.
Just one option for you if you also need a multi meter.
Melson, I have two Flukes and a new SouthWire meter.
I have to admit, the post has got me very curious about frequency problems.
Just that I am not sure that I am curious enough to invest $225 in a Hantek scope from Amazon
 

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I use a Berger or Granite's power analyzer depending task an can tell you there are very few mfg's that will meet a TRUE 5% THD test. Even some of the major mfgs who deal in much bigger iron have issues meeting that spec, even though 5 is printed on their spec charts. One day the industry will clamp down, however as long as price point is driving the market the lies will continue.
 
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By the way, @tabora , I sold my Dranitz gear on eBay when I retired. Sweet stuff! I sure wish I kept it; it was the best monitoring & recording! Better than anything Fluke, on par with Tektronics. Can I borrow it and maybe promise to give it back? <GRIN>
Would you believe that I bought mine on eBay for $29.99 plus $19 shipping? I purchased a full cable set piecemeal VERY inexpensively, and it uses the same paper spools as my credit card machine.
 

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Would you believe that I bought mine on eBay for $29.99 plus $19 shipping? I purchased a full cable set piecemeal VERY inexpensively, and it uses the same paper spools as my credit card machine.
Actually, I AM a bit surprised. What a steal!
Whoever sold it either didn't know how good even the basic and ancient Dranetz are.. or didn't care. I paid $12 *thousand* (thousand!) for a new three phase jobber back in the late 80's.
How are the batteries doing?
 

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Actually, I AM a bit surprised. What a steal!
Whoever sold it either didn't know how good even the basic and ancient Dranetz are.. or didn't care. I paid $12 *thousand* (thousand!) for a new three phase jobber back in the late 80's.
How are the batteries doing?
Yup, the full retail on my PP1 unit (which can also do 3-phase - every power permutation up to 600V) with all the accessories was about $12K around the turn of the century... It had a dead battery and about every error message showing on boot; however, based on prior experience I knew it probably just needed to be reset and have the simple recalibrations done. So, yeah, practically grand theft by auction! My old basic Dranetz cost over $8K back in the 1980s.

The NiCD 12V 10cell battery pack in the PP1 was dead, so I purchased a same-size NiMH 12V pack and external charging unit for it (at $25 it was about 20% of the cost of the replacement Dranetz NiCD pack).
 

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Well, this post really got my curiosity up.
I went on Ebay and looked for a Techtronic dual trace scope as I used one many years in my work.
Well as luck would have it there was a used one up for bid.
Starting bid was $80 so I bid that amount plus $20 delivery.
I got busy the next day and the biding ended.
Well, I guess you know I missed it.
The scope sold for $135 and I was really let down that I had not paid better attention.
Now my curiosity is still hanging in there too.
 

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@iowagold: I spent Saturday evening going thru the posted Techtronic scopes.
I got frustrated and a little confused.
Many were obviously used and used and used to the point that I was leery of biding.
Too much use and the tube gets cloudy and eventually stops performing.
I just gave up and let it go.
I did however bid on the one you pointed to.
I am not really wanting to win a bid unless I can get one on the low end.
I prefer the Techtronic over the new hand held units.
 

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ToolLover, if your needs are modest there are cordless digital Fluke models that are quite good enough, and no worries about gnd loops. Actually the 1mhz cordless fluke "Scopemeter" I kept is great for general purposes. So maybe cast a slightly broader net?
 

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@ToolLover
yea there used to be a place in desmoines iowa that re mfg the crt.
cool for good equipment!!
new spray inside and new gun if it needed it for less than 200 bucks!!
nice for expensive test gear!!

I like the old crt trace... unless you have a high resolution tft display..

I have been looking at Bluetooth scopes that will work with ipad pro..
wireless so no chance on frying the $1000.00 pad..

the classic analog test gear works for me..
faster than all the setup menus!!
lol!
 

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Ok, I'll play.
Using a 120V to 12V isolation transformer to take the readings.
Generac GP 15000.
1500 watt load
8548


3000 Watt load

8549

Utility Power
8550
 

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wow top 2 wave forms look like crap!
bottom one looks ok.
as long at the time factor was good (60hz)
 

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It is actually used to run my "all electric" house during power outages when I need central air or heat.
I live in a rural area and do not have NG or propane available.
I have a 2 1/2 ton heat pump to supply heat and air.
The GP15000E handles the job well. I have a 50 AMP inlet connected to my breaker box with an interlock switch.
Nothing complains {nor my wife} while on the generator. Just have to shed loads at times as needed.
Also have two UPS units that are set to "low sensitivity" that work without any complaints or switching.
I agree, it is not an inverter quality sine wave and I don't have the equipment required to measure the THD but it does put out very stable voltage and HZ at all loads. Those, I watch closely.
During mild weather I use a Champion Power Equipment 100519 6250-Watt Open Frame Inverter generator to save fuel. The GP15000E is a gas hog. Many hours on it and have not had an issue.
 
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