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Author Topic: Flickering lights  (Read 20691 times)

Procrustes

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Flickering lights
« on: January 24, 2006, 04:33:28 AM »
cujet wrote:

One thing I have noticed is that the lights flicker a bit with the lister. I believe it is due to the power stroke(s) causing a slight speed change. Meaning that there is not enough flywheel. Many have noticed this on the single cylinder listers also.

(http://listerengine.com/smf/index.php?topic=2.msg66#msg66)

Who else has seen this?  Is it a common problem?  How big a problem is it?  And would a twin have an advantage here over a single?

As always, thanks in advance for any help.

jimmer

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Re: Flickering lights
« Reply #1 on: January 24, 2006, 04:49:53 AM »
The flicker kinda goes with the single cylinder power stroke.

It is mainly an incandescent light problem. The best fix is to use the newer compact fluorescent lights.

Jim

Procrustes

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Re: Flickering lights
« Reply #2 on: January 24, 2006, 05:05:02 AM »
I use the flourescents all right.  So you don't see other symptoms then?

Incidentally cujet was talking about a twin there.

BruceM

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Re: Flickering lights
« Reply #3 on: January 24, 2006, 04:58:24 PM »
I don't believe the compact flourescents would solve the 10.8 Hz voltage droop. They don't have enough bulk DC storage capacitor to deal with it.  But maybe there's something going on I don't understand.

There would also be an interesting harmonic between the 4 poled generator rpm 1800 rpm and the engine's 650 rpm.  An occasional beat which might be an issue.

Bruce

jimmer

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Re: Flickering lights
« Reply #4 on: January 24, 2006, 05:17:45 PM »
Well all I can say is with my 8/1-ST5, any incandescent light I use flickers.

The compact fluorescent don't (screw-in type).

Jim

Procrustes

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Re: Flickering lights
« Reply #5 on: January 24, 2006, 05:39:57 PM »
I don't believe the compact flourescents would solve the 10.8 Hz voltage droop. They don't have enough bulk DC storage capacitor to deal with it.  But maybe there's something going on I don't understand.

There would also be an interesting harmonic between the 4 poled generator rpm 1800 rpm and the engine's 650 rpm.  An occasional beat which might be an issue.

This is the first I've heard of a 10.8 Hz droop.  That's more substantial than I'd assumed.  How big of a drawback is it?  Do twins halve this effect?

Bruce, could you elaborate on the 1800/650 harmonic you mentioned?  I don't know anything about this.

Listeroidsusa

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Re: Flickering lights
« Reply #6 on: January 25, 2006, 01:58:10 AM »
I would tend to think it is more in the generator than the engine. In the past I rewound electric motors and generators. Many times the flicker was due to the pole spacing in the generator. Many motors and generators use skewed windings so the voltage overlaps. 360 electrical degrees = one pole so if there is not a constant current produced there may be a portion of the cycle that is in transition more so in a single phase generator than in the balanced power flow of a 3 phase machine. My 6/1 GM-90 does not have a voltage or frequency droop and my lights work well, but it is a 3 phase unit. My governor holds the frequency at 1/10 of one cycle so frequency droop is not an issue.

Mike

t19

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Re: Flickering lights
« Reply #7 on: January 25, 2006, 02:44:47 AM »
I'm with Mike, sounds like a Gen head problem to me
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hotater

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Re: Flickering lights
« Reply #8 on: January 25, 2006, 03:21:30 AM »
I've had flickering lights of all kinds for seven months, but there's about to be a genhead change and I'll report on the difference.
  I had always *assumed* it was power stroke induced.  The Hz stays plus or minus .7 and voltage at nearly 130, but  lights of all types flicker in time with the engine's thump.
7200 hrs on 6-1/5Kw, FuKing Listeroid,
Currently running PS-Kit 6-1/5Kw...and some MPs and Chanfas and diesel snowplows and trucks and stuff.

Procrustes

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Re: Flickering lights
« Reply #9 on: January 27, 2006, 06:29:47 AM »
In "Lister Longevity" George B says that this flickering is due to the power stroke, and specifically mentions incandescents.  Further, flywheel weight mitigates the problem, as does not running a light load on the genset, as does the V belt (though it introduces more loss vs. serpentine).

This is page 86 of my copy.

BruceM

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Re: Flickering lights
« Reply #10 on: January 28, 2006, 01:21:26 AM »
Part of the problem in discussing flicker is that people's ability to see flicker of various frequencies varies greatly.  So a report of "bad flicker" or "no flicker" depends on that individual unless the measurement was via photodiode and an oscilliscope!

Edit 1/28: Since flicker sensitivity generally decreases with increasing frequency, it's not surprising that the faster RPM engines have less problem with flicker than the 650 rpm engines. The increased effectiveness of the flywheels at higher rpm has also got to help. So there's one point (maybe important if lighting is a big issue) for higher rpm.(end edit) 

Most frequency meters are going to be looking at a time weighted average, either from the meter movement itself.  So just because a meter says's the average frequency is within 0.1 Hz doesn't mean that there isn't variation of voltage/light output at 10.8 Hz.  There most certainly is.

Even at just 0.5% modulation at 60 Hz,, there are folks who will be bothered. Often these are the people who subjectively "don't like computers", or "just don't like LCD displays". (LCD's are internally refreshed at 60 Hz regardless of the computer's video frequency and have 0.5-1% modulation.)

At lower frequencies like 10.8 Hz,, the sensitivity to light intensity fluctuation (modulation) is typically even greater, and I wouldn't be surprised to see some people notice even 0.1% modulation at that frequency. This level of modulation of peak voltage you would certainly see from acceleration of engine/generator at power stroke time. 

As to the "beat" between the 10.8 Hz engine and the generator's 60Hz output:   When the increasing velocity at the power stroke coincides with peaking output wave of the generator, you will get an abnormally high peak voltage. This beat will be a well below 10.8 Hz, and I don't know if it's an issue.  Edit:  Since this beat is sub hertz and the generator power pulse rate is so much higher, I think I was off base on this. 





« Last Edit: January 28, 2006, 03:34:48 PM by BruceM »

Tom

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Re: Flickering lights
« Reply #11 on: January 28, 2006, 06:33:51 PM »
Another source of flicker can be dirty slip rings. I had this problem with an Onan and solved it with an abrasive stick purchased from the generator shop. Just rub the stick on the slip rings with the generator spining. However if your flicker is in time with the power stroke well, dirt is probably not the problem. I have not used my rig for lights at night so I don't know if mine does it.l
Tom
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solarguy

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Re: Flickering lights
« Reply #12 on: February 18, 2006, 10:31:40 PM »
The few incandescents we have flicker very noticably.  The "old fashioned" 4 ft shop fluorescent lights also flicker a lot.  The CF fluorescent bulbs flicker hardly at all.

A twin will definitely have faster flicker.  1000 rpm prime movers will also have faster flicker.  Five power strokes per second is the root cause of my problem.  I rarely notice it any more.

Back in the day, there was such a thing as 20 Hz AC as grid power.  It didn't last long and was pretty localized.  One of the reasons it went away was because of the annoying flicker.

Good luck and have fun!

troy

Doug

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Re: Flickering lights
« Reply #13 on: February 19, 2006, 02:40:10 AM »
This might come as a shock to you solar guy but 25 Hz power was around for a lot longer than you may realize. We only stopped generating about 15 years ago because we finaly didn't need it any more. 25 hz power was realy nice in industrial use because it allowed you to run low speed drives with 4 and 6 pole machines. It was also easy to generate and had lower line looses.
25 Hz machines had more than twice the iron in them than 60 Hz, as a result the iron ran cooler and insulation lasted longer.

And then there was the 25 flicker.....
Something only an industrial electrician could love I guess.

I will make an effort to go to 3800 level 6 shaft hoist room and snap some photos to post of the all the old 1930s open switch gear and 25 cycle machinery, its kind of like stepping back in time. The whole room has a massive Lister feel to it I think you guys might like, giant iron castings in black and green with huge handles, ball weight goveners and large dials and meters. After 70 years and decades of neglect it looks as if you could simply do a little sweeping, turn on some 25 cycle and start skipping ore and hoisting again.

Doug

trigzy

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Re: Flickering lights
« Reply #14 on: February 19, 2006, 02:46:22 AM »
Doug,
         Last time I had access to the information, there was still some 25Hz generation in Northern Ontario, providing only a few customers who have large machinery similiar to what you have described.

There's even some 25Hz generators at Sir Adam Beck I, (in Niagara Falls, ON) that are matched to a M-G set to convert it to 60Hz

Steve
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