PTO generators and slight flickering of lights

allischalmers6 · Jun 26, 2013

I was reading some time ago that a Johnny Popper is not good to run a pto generator due to harmonic distortion. I It said that you can see the power strokes and the non powerstrokes in a johnny popper. Why is that? Is harmonic distortion the flicker we see in the lights?

Billy Shafer · Jun 26, 2013

Some single cylinder engines can be hard on voltage output. Onan used a set of anti flicker points. To help wit the output. Some generators have a stability pot on them to help take out the flicker.

Bob Bancroft · Jun 26, 2013

I don't know the answer. But I do notice the lights aren't steady when running on my PTO alternator powered by an AC C, like they are on the power line.
Although it does seem like if I can get enough load on it so the tractor is working, and the slap is taken put of the drive line, chain, etc., it helps.

Bob M · Jun 26, 2013

The flicker often seen in lights powered by a generator pulled by a 2 cylinder Deere tractor is FREQUENCY distortion. It is caused by RPM variation between power and non-power portions of crankshaft rotation. As generator voltage output is proportional to RPM it can cause a visible flicker in incandescent lights as the RPM varies up and down with each pair of power strokes.

It's most noticeble with the slowest turning diesels (R, 80, 820, etc) and less noticeable with the higher RPM small gassers (H, M, 40, 420, etc). And it's essentially non-existent on a generator pulled by a fast-spinning 6 cylinder like a 4020.

Incidentally HARMONIC distortion is the distortion of current/voltage waveform from an ideal sine wave. You need an oscilloscope or other waveform analyzer to detect it. Harmonic distortion does not cause lights to flicker.

Mike M · Jun 27, 2013

Ohio Edison must be using JD 2 poppers then !! LOL My lights flicker worse with them then when my powers out and I fire up the old Army genset. 1945 powered by a Willys 4 cyl.

I have powered our pto gen. with some 2 cyls. before. They did allright but by far not as good as a 4 or 6 cyl.

buickanddeere · Jun 27, 2013

We a 30KW pto generator and some 4.8KW milk house heaters if required. That we load the two cylinders with. At least once a year the lesser used tractors are run up to load and temp for an hour.
The 40, 50""s , 70D, 720D, 80 and 435 have little to no obvious flicker. The 60 and 70G have a nasty flicker.

ss55 · Jun 27, 2013

Could part of the flicker also be caused by the engine's governor responses or governor "hunting" as well as by the uneven firing order of the cylinders on a 2 cylinder Deere tractor?

If the flickering is caused by the uneven firing order:
At around 900 rpm a 4 cycle engine with 180-540 degree firing would "pop" about 450 times per minute or 7.5 times per seconds. The lights would flicker at a steady 7.5 Hertz.

If the lights flicker at a slower rates it could be the governor's response to a less than full load.

PTO generators and slight flickering of lights

allischalmers6

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Billy Shafer

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Bob Bancroft

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Bob M

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Mike M

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buickanddeere

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ss55

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