Are Inverter Refrigerators immune to what's known as Dirty Power?

[Apothecary]

I can state unequivocally that my side by side Frigidaire refrigerator, Model # FRS26TS7DB2, manufactured July of 2004 would run on the generator mentioned above, but would not get cold.
I discontinued trying to use that generator with that refrigerator because I assumed it would damage it. I subsequently had the freezer fan motor fail. Related? Not sure.
Maybe the fan that blows air across the coils was unable to run properly with that generator?

That same refrigerator is still working today (after replacing the fan motor).

I would be interested to know what the THD is for this generator. And how that compares to other similar generators.
As it stands now, I only consider it usable for the water heater and incandescent lighting.

 

[Nigel Goodwin]

I would be interested to know what the THD is for this generator. And how that compares to other similar generators.

I would suggest that the output you've shown (was it off or on load?) is absolutely horrible, surely an AC generator should put out a pretty decent looking sine wave?.

 

[Reloadron]

Maybe someone with a better understanding of harmonics can tell us if this is a potentially harmful Sinusoidal wave form.
It has "some" noise apparently, but overall not a terribly bad waveform. I didn't see any major spiking of voltage.

OK, setting the newer inverter generators aside for a few moments. The waveform you posted does not really seem all that bad to me. However, this also depends on what load the waveform is driving. Let's for example take a 60 Hz AC Induction Motor. The motor is likely not even going to "see" the harmonics on that waveform or care about the presence of the harmonics. The typical AC induction motor which is a 2 Pole motor running at 120 VAC works out like this and the same formula applies to a generator, a non inverting type generator:

Generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120 Conversely, P = 120*f/N

60 Hz. = 3600 * 2 / 120

So a common two pole motor running at 60 Hz will have a rotational speed of 3600 RPM but allowing for some motor pole slips the common RPM is 3450. The motor is not going to see or respond fast enough to the harmonics you see. As long as the true RMS voltage is correct the motor will run just fine.

When we get into the inverter world a few things change. We take an AC voltage and convert it to DC much like an automotive alternator converts the AC it generates to DC. Then the DC is filtered and cleaned up. That DC power is used to drive and inverter which converts the DC back to AC at a fixed frequency.

When measuring the AC output of a generator, be it inverter or non-inverter type we care about the RMS voltage and the wave shape but both should be measured under a load. Anyway, the wave shape you posted does not look all that bad to me as I have seen much worse do just fine running electronics and motors. There are instruments designed around measuring power quality but as I have said before you really won't see much or come away with any quantative numbers using a scope.

Ron

 

[debe]

Its not a sinusoidal wave form, its a triangular nothing like what mains power is. Also power boards in Inverter generators can fail especialy when loads are dropped on & off. I have thrown out several inverter generators with failed inverter boards as the replacement price is too high.

 

[Apothecary]

They didn't specify which one, but here's another generator waveform....presumably NON Inverter

 

[Reloadron]

I think pretty much all of them will look about like that. Some of it is likely brush noise from where the field is applied through slip rings. I still do not see where it matters much as I ran this house plenty of times on my old 4.0 KW unit. I never had appliance failures I could attribute to the generator.

Ron