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I know that an inverter alone can be a "modified sine wave" or "pure sine wave", but the price difference is huge. Does this apply to "inverter generators"?

When these companies market it as "inverter generator", does it mean that it is pure sine wave? I am looking at this Ryobi Bluetooth 2300-Watt (RYi2300BTA) generator, but there is no information/spec on their web site or owner's manual that I can confirm if this is pure sine wave or not. Only Honda specifically says it's pure sine wave.

  • I modified your question title to make it less of a product spec question, which tends toward off-topic. – isherwood Apr 30 '18 at 20:13
  • It's easier to teach a violin player the bongoes than the other way around. What is the sensitive load? – Harper - Reinstate Monica Oct 28 '19 at 18:21
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Most inverter generators are a "good enough" sine wave.

I think you're missing the point of inverter generators. The root problem is that regular gas generators cannot produce a "clean" sine wave because they change speeds slightly during operation. When the speed changes, the wave changes slightly. This isn't a problem for regular electrical devices like incandescent lights, power tools, "basic" refrigerators, etc. They merely need the flow, not so much the sine wave.

Anything in the "consumer electronics" category, however, is not so lucky. Most of these devices rely on the sine wave for timing, and normal generators won't cut it here. I remember trying to watch TV on a conventional generator after a hurricane a couple of decades ago. The sound was fine, but the tube TV couldn't fill the whole screen. The TV ran fine once power was restored.

Inverters fix the issue by inverting DC to AC. As the output is consistent, consumer electronics will run relatively well on them. That's the main reason you buy these types of generators. If consumer electronics won't run on them, they're overpriced regular generators.

"Pure Sine Wave" seems to be a marketing term

Having looked at several inverter generators, "pure" and "clean" are only sparsely used. This Champion generator says

Clean Power for Sensitive Electronics. Includes two 120V 20A household outlets with clean electricity (less than 3% THD)

This pricey Briggs and Stratton generator doesn't mention sine waves, clean or THD. It merely says

The inverter generator technology supplies consistent power for essential home appliances, including sensitive electronics.

And finally, your Ryobi RYi2300BTA with it's "pure sine wave"

THD < 5%

The real spec to pay attention to is Total Harmonic Distortion

Total Harmonic Distortion is a heavy concept, but it is a real metric

Total Harmonic Distortion (THD) is the stated measurement related to the quality of electricity.The amount of THD will influence how your equipment may respond or perform.

When power quality is discussed, you will hear terms like “clean electricity” and sine wave power. What these refer to is the lower harmonic distortion of the electrical AC wave and the ability to take square wave generated electrical power and smooth the edges to produce a phase that is smoother and less square.

“Clean electricity” is considered good with a THD of less than 6% and often stated or promoted at 5% or less.

Sadly, most marketing ignores this metric. They all likely refer to a THD of less than 5%.

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  • Great answer. Thanks for the clarity. +1 – M.Mat Oct 28 '19 at 5:58
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An inverter generator is not a pure sine-wave generator. See Ken Dupree's comment on this web page:

https://rurallivingtoday.com/generators/power-inverters-vs-generators-which-best/

There's a lot of good info on this page which depending on your usage will confirm whether your specific generator is appropriate for you intended use.

Inverter Gen (IG) vs Std Gen (SG)

  • IGs are smaller, lighter, & quieter
  • IGs adjust speed to the power needed
  • IGs convert DC to AC power using electronics
  • SGs are noisy, heavy & mounted on frame & wheels
  • IGs save up to 40% on fuel
  • IGs reduce exhaust
  • SGs run at 3600 rpm regardless of load
  • IGs, produce AC by converting DC to AC
  • SGs are better for high power out
  • SGs are cheaper; IGs are higher priced
  • IGs produce a “simulated” AC sine wave
  • IGs do well creating a sine wave, but they’re not perfect; electronics don't like their sawtooth effect
  • SGs produce a pure sine wave
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  • 1
    @peinal, thanks for the summary; I took the liberty of moving it from your comment into the answer, and added some formatting for easier readability. – Nate S. Oct 28 '19 at 17:20
  • This implies that SG's are better for sensitive electronics, which is absolutely not true. SGs may produce a truly analog wave, but the lack of consistent 60Hz presents a problem. – trpt4him Aug 1 at 15:15
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It depends on what type of IG you get. I will break it down for you in general terms. In North America, we use 110 VAC at 60Hz. That means the waveform coming to our household outlet is alternating 60 times per sec ;)[ In Europe it may be 220 V 50 times as they use 50 Hz load]. How IG achieves this is fairly simple (or complicated depending on your understanding of the science/principle). Most InvGen have 3 phase permanent magnet alternator in delta configuration - meaning 3 sets of stator wired at 120 degree out of phase and magnets as rotor. when the gas engine turns the rotor, the coils produces 3 pure sine wave 120 degree out of phase at whatever frequency the engine is turning. Generally this is 260 VAC and RPM/60 Hz. This is then send via rectifier to produce almost DC 260VDC (with some ripple). This is where the inverter comes into play. It then turns that DC signal to 110VAC at 60Hz with MOSFETs and all that doodad. An expensive inverter could convert that DC into close to true sine wave while lesser ones would not.

That being said, a conventional generator produces pure sine wave when no load. They try to maintain RPM of 3600. Cause that would be 60 cycle per sec or 60 hz which is what we would use in NA. Again, cheaper ConGens do not have sophisticated regulators etc etc

In theory.

but, if you hook up an oscilloscope you will find out...

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  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. – Daniel Griscom Jan 20 at 19:56
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Apart from how the equipment to be powered derives it's own timing, there is a benefit of not having the line frequency tied to the engine rpm and that is noise reduction. Under less than full load, the engine can run at reduced rpm without impacting the AC line rate. I suspect it saves fuel too. But frequency is only one aspect of AC power. The generator output can have a fundamental frequency of almost exactly 60 Hz and still not be even close to clean enough. So the question of purity or distortion is not missing the point at all. Some equipment just won't run right on a modified sine.

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