It's not always black-and-white. A good inverter generator will have an extremely clean sine output. But, at least considering standalone DC->AC inverters, low-end inverters will be ugly modified sine wave outputs. Better inverters are pure sine output.
I'd imagine there are inexpensive inverter generators that are modified sine wave outputs. But generally, yes, an inverter generator should have a cleaner electrical output than a typical fixed-RPM ("contractor") generator.
I have a Hitachi oscilloscope. I have looked at the wave form for my inductor non inverter generator. It was clearly modified sine wave and very blocky. I use that one only for the water heater and AC incandescent lighting. No sensitive electronics. WAG....10-15% THD
Because my leads were misplaced and I just ordered a new set of probes, I haven't checked the waveform from my inverter generators.
Typically, inverter Generators need to have a THD of less than 6% to be considered safe for sensitive electronics. While people say they have "safely" used non inverter generators on sensitive electronics, what they may be unaware of is that accelerated wear (mostly in the form of heat) can occur which can shorten the life of the electronics even though it may not have failed at the time.
It's sort of like driving a car with the tires far out of alignment. You can still drive it, but the wear on the tires will be accelerated.
After I get the waveform output for my inverter generators I'll post the results and pictures of the waveforms.
If ANY of my inverter generators produce more than 6% THD, then the primary benefit would only be fuel efficiency. The large capacitors and electronics are supposed to smooth out the harmonics to below 6%
I have 3 inverter generators. A HarborFreight Predator 3500, a Pulsar PG2000is and a Honda eu2000i. I'll be checking the waveforms from all 3.
I expect all three to have fairly nice sinusoidal waveforms compared to the non inverter generator.
That said, When I CALLED Pulsar and spoke to someone in their cust serv dept, they said their inverter generators produce 5% THD at 50% load and as much as 8% THD at full load. BUT....in the Owners Manual under SPECS, it says Less than or equal to 3% THD. I think the technician was looking at NON Inverter specs. But as others have pointed out, the simple fact that you have an inverter generator is not a guarantee that the output is "clean".
HarborFreight Claims their Predator 3500 Inverter Generator to have only 2% THD (load unspecified). That seems to be an odd claim.
The Honda eu2000i is said to have only about 1% THD.
While I won't have the precise THD, it will be fairly self evident from the waveform the quality of the power output. Well, to some degree.
What might be of most value from all this is that even cheap inverter Gensets today have THD that is very acceptable for sensitive electronics.....provided they are being honest in their published THD numbers. Anything below 6% THD is generally considered safe for all electronics.
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