I decided to throw the scope on as many generators and inverters I could easily get my hands on to compare the quality of their output waveform.   Equipment used was a Rigol DS1054Z scope and a 1300V differential probe set.  Loads were purely resistive, so no waveform distortion from switching power suppliers or inductive loads.  I used either a 40watt soldering iron for the small power sources or a space heater for the larger sources.

Scope:

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1. First up was the incoming line power to my house.  Now I can't control the load on this source since I share it with the neighbors and there are quite a few devices plugged in at my home.  However we are just going to use it for base-line reference.


Overall, not bad.  Minor distortion.

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2. Xantrex ProSine 2.0, 2000 watt pure sine inverter/charger.  (this unit is older, before Xantrex products were made by the lowest bidder in China)


Real clean signal, very stable with load fluctuations.

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3. Xantrex ProWatt 600, This is a low-cost 600watt pure sine inverter.  About 1/10th the price of the ProSine2.0


Not great, but passable for sensitive electronics.  Clearly not the quality of higher end inverters

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4. Vector MAXX 700, A big box store modified sine wave inverter I keep in the truck for running a grinder in the field.  (off road weld repairs)  It runs the grinder very well, no start issues.  Always works when needed, but motors run a little slower than line power and electronics "hum" more.  Clearly not desirable for long term use.


Signal is clean for a modified sine wave, but those big, rapid jumps in voltage are hell on electronics.

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5. Honda EU2000i, A 1600 watt (cont) inverter generator that is the defacto standard for clean power and low fuel consumption.  But how good is it really?


The answer is "very good".  It was the only unit I tested that rivaled the ProSine2.0.   I would still give the edge to the ProSine2.0 based on its ability to handle 2x the surge load as the Honda and its faster response to load changes.  The Honda is just handicapped by its mechanical nature when it comes to load reaction.  BUT, this is still a great source of clean power.

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6. Libby MEP-802a, a 5000 watt (6250 by convential standards) 1800 rpm brushless diesel generator.  This is not a cheap brushless with no AVR.  These are a true industrial generator designed to provide clean power in harsh conditions. (including EMP resistance)  This is the most rugged piece of hardware I own.  These units can supply straight 120v, 120/240v split-phase (house power), or 120/208v 3-phase.  I tested this unit at 240v with a 3000 watt load.


Pretty clean power, some harmonic distortion, likely due to the winding pitch of the stator.  Overall not bad.

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7. Harbor Freight Predator 3500, a 3000 watt inverter generator.  A friend of mine just purchased one of these, so we tore into and were pretty impressed with the build quality.  Fuel consumption and noise are notably higher than a comparable Honda 3000i, but the cost is less than half.  And this thing still beats the pants off of your average open-frame 3600 rpm generator.


We had expected to see a noticeable quality difference in the power output of this low cost unit.  Boy were we surprised.  Output was very clean, with or without load.  Only a minor distortion at the zero-crossing point.  Vrms and frequency were dead on.  It even comes with a useful display.

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So the one unit I couldn't find to test was your average 3600 rpm noise and fume generator.  I have a friend that has access to one we will test in the future, but for now, check out the scope attached to a Coleman 5000 watt open-frame unit
[youtube]QNo1mUCpQnI?t=19[/youtube]

A related question, I have a Prosine 2.0 that is now giving me a "memory fault error".  Is this something simple or will it be big bucks shipping it back to Prosine so *they* can do something simple?

Fantastic info! Thanks for posting it!

Curious what you find out. I have one that doesn't produce power.

Details on 1300V differential probe.

My in-laws repair generators daily, but it looks like it'd cost me about $500 in equipment I'd never use again...

I have a 15,000 watt GenPro that I'd love it check too, for the house backup. Ambien Walrus will be claim to another victim here eventually

We went through several EU2000i models at work, and they all leaked gas badly and were hard to start. Three of them needed new
inverters and two used a lot of oil probably from all of the starter fluid we had to use to get them to start.  I'd recommend buying nearly anything else besides a Honda.z

What if you hooked a ProSine 2.0 Inverter up to a dirty power generator like the Coleman sited.  Would the power coming out the inverter be cleaned up to look like it didn't see the original dirty power from the power source generator.

I have a Ridgid 5000Watt gas engine gen bought from HD that I suspect puts out dirty power.  Probably be better to sell it but was wondering if I could clean it up by running thru a quality inverter. Thanks

Fascinating. Thanks

fantastic info thank you

Thanks OP!

ETA:  No pictures, but a friend bought one of the Sportsman generators from Home Depot late last year when they were on sale.  He told me that it generates horrible RFI - about an S6 with HF radios.  He then used an iPower generator (Honda clone) that was bought on Amazon and no RFI.

Great thread!

Good info and thank you OP!!!!

That Vector is more close to a modified square wave. LOL

Unfortunately I haven't heard of any success stories repairing ProSines, most guys either can't get the parts or it's too expensive to fix.

Most are later model units made after Xantrex lowered their quality standards.

I bought this unit from Amazon.  Now I dont have to worry about grounding issues blowing up my scope.

Probe

Interesting, that's a bummer you had so many issues.  Most people I talk to love their units.  I will say it takes 10-20 pulls to get it started after sitting a long period of time.  The fuel pump is a diaphragm type driven by crankcase pressure.  I would avoid ether if possible.  It can strip oil from the cylinder walls and accelerare ring wear, leading to low compression and oil burn.

Unfortunately, that will not work. The ProSine either passes through line power or if the power is unacceptable,  it switches to its internal supply. But it cannot condition noisy power into clean power.

Great thread RockRanger! Wish I was in CO, I'd offer up my new Champion inverter/generator for you to test if you were interested? Me and quite a few other people got in on a great deal that home depot had back when they were on sale for $300.

https://www.ar15.com/forums/General/Harbor-Freight-Inverter-Generators-NOW-OFFICIAL-BUDGET-GENERATOR-THREAD/5-2032324/?page=47#i80607691

I'm curious how "clean" the power is for running a 5,000 btu window ac unit, fridge, computer ups etc...

I'd test that if you were around!

Curious to see more results from 3600 rpm gennys. I have 3 of them, ranging from bottom end Chinese import to high end advertised with "clean power technology".

I'm impressed with your scope on the Predator 3500.  I figured it would be a little more fuzzy. Still, I love mine.

IME, the power quality of non-inverter generators - particularly the non-AVR-equipped "brushless" variety - can vary TREMENDOUSLY with applied load.

At zero load, some of them are absolutely hideous - but look a lot better with just a few dozen watts applied.

I played with that a bit.  I couldn't influence the tested power sources.

Re-running the test with a non-AVR brushless would be interesting.

(Bump for when I finally get around to dragging out the scope for some waveform pix)

I have a non-inverter generator.  It pops some of the GFIs in my circuit panel.  Could the not very clean power be the reason?

I have found that when starting an EUXXXX that has been sitting empty that if you fill it, set it to run, then pull the cord twice then let it sit about 5 minutes.  Mine start right up everytime I follow this procedure.

Also make sure the jets in the carb are clean.  This is a weak spot in the design and I find I have to service the jet fairly often.  After a several day run from a power outage due to a hurricane, I always pull the carb out and clean the jets.  Takes maybe 15 minutes and ensures the unit will run smooth the next time I need it.  There are Youtube vids showing exactly how to do this.

GFCI's and UPS's tend to get fussy if the generator's Neutral and Ground wires aren't connected (or "bonded") together.

When you're connected to utility power, these two wires are typically connected together at the main breaker box or main disconnect switch.

However, a lot generators don't have them connected internally - which means that you have to make the connection externally.

Is that something I can do?  It's a PITA because my fridge is on one of the GFI circuits.

Yes, you can connect the Neutral and Ground wires on the cable you use to connect your generator to your panel. Plug-in adapters that do the same thing are also available - Here's an example.

Thank you for the informative post. I was actually kinda disappointed in the output of the MEP802. I expected it to be damned near perfect.

I have an 803A and it has been an awesome piece of equipment and just today came into owning that Xantrex 600 watt inverter so interesting to see the output of them on a scope.

Are those pics no load?

Thanks Skibane, that will probably fix the issue.

I'll bet that my Predator 4000 has a similar output. Thanks for the test results!

Interesting, but let's say I'm not an electrical guy but interested to learn more about it. I have an inverter generator mostly because I bought it cheap locally and I had heard it was quieter to run and used less gas. What does clean power mean? less likely to blow up sensitive stuff or is there more to it than that?

Also what's the deal with that beefy ass .mil generator? That seems like it would be fun to have living in a shed for whole house power.

It means that there are no power "spikes" in the wave form. A perfect generator would have a pure sine wave output, even when producing full power.



OTOH "dirty" power looks like a porcupine got into the oscilloscope.



And it is dangerous! One Field Day* the club had a very very old generator, like possibly WWII, or at the latest, Korean War. It kept tripping the GFI power outlets on the distribution units it was attached to. Suddenly all the electricity went away in my tent, and smoke appeared! It had burned a nickle-sized hole in the (admittedly cheap) power strip/surge protector! Also, my $200 monitor protected its $0.25 fuse by blowing out somewhere inside; the power surge was so fast that the fuse didn't even see it.

*ham radio activity, many use generators instead of house mains.

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Found some more information on this page:

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

Pepco ($5.54/month + $0.10126/kWh + taxes & fees)


APC Back-UPS 650


APC Back-UPS Pro 500


APC Smart-UPS 700
No Load


80% Load


Alton AT04141/120 Generator No Load


Alton AT04141/120 Generator 60w load

I have access to a Champion Inverter Generator (purchased from the recent Home Depot deal) and an old oscilloscope.   I will get the two together and add some pics to this if you want.

2Hut8

That would be great.

I'd love to see that as well. Subscribing...

One interesting observation about both of the Champion inverter models shown above:

When starved for gas, the engine stumbles and then over-revs (same as any other gas engine).

During the moment the engine is over-revving, the AC output voltage and frequency still stays constant - which is good. No potentially damaging high voltage peaks.

However, if the engine stumbles enough, the AC output voltage sags (although frequency still stays constant) - which could cause problems with some loads (i.e., stalled compressors).

It's unavoidable (no generator is capable of maintaining full output when the engine is close to stalling) - but it's definitely something to be aware of.

BOTTOM LINE: Don't let your generator run out of gas with a sensitive load connected to it.

It takes about 22 GENTLE pulls to prime the carb of an EU1000 or 2000.

Reason, is the crankcase vacuum operates the fuel pump.

There is an overflow tube that dumps excessive fuel when the carb is overfilled, that can happen if the genny is shaken much and the float bounces around.

Most folks don't understand this and do what your company did.

We have 4 Hondas and have run them for years with no issues, except silica dust clogging the carb. An small inline filter solved the issue. See my post in the SF.

We use exclusively alcohol laced fuel, with none of the issues the ninnies fret about.

ETA: This model occasionally goes on sale for around $150 - Very impressive performance for the price.

However, long-term reliability is unknown.

Most well pumps use 240v so if yours does, make sure your generator can make 240v