Lister Engines > Listeroid Engines

My fix for Listeroid light flicker

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veggie:
I tried to evaluate the effect of the rotational speed variation from the pulse of a large displacement single cylinder four cycle engine (AKA Lister).

From my estimations (that's all they are, just estimations), the power pulse and resulting momentary generator RPM change on a lister(oid) with a 3600 rpm AC generator head are considerable.

Lets assume that the engine pulse (or speed drop/increase) is the equivalent to a
momentary "bump" of 2 rpm at the engine. (That's a guess on my part).
It's not really important because what is being tested here is the relationship
between two generator speeds. The comparison between 1800 and 3600 would
stay the same regardless of the exact speed "bump" value.

3500 RPM Generator Head:
ENGINE RPM      RATIO         GEN. RPM
================================
650                       5.53                 3600
648                       5.53                 3583 <---- a change of 17 RPM !


Now lets look at and 1800 rpm head...

ENGINE RPM      RATIO         GEN. RPM
================================
650                       2.77                 1800
648                       2.77                 1794 <---- a change of 6 RPM

*************************************************************************************************

OK, now what if it were a bit more pronounced.
Say on a power stroke the lurch causes a equivalent 2 rpm bump, and on the coasting cycle the target speed drops by 2 rpm.
(Assuming the generator is under load so there is considerable resistance to rotation). The flywheel inertia is attempting to overcome the drag from the Generator head, but there is still some drop in rpm). A total of 4 rpm from power stroke to the end of the coasting cycle.
Because of the belt ratio, the speed change is amplified 5.53 times !

3500 RPM Generator Head: (4 rpm interruption)
ENGINE RPM      RATIO         GEN. RPM
================================
650                       5.53                 3600
646                       5.53                 3583 <---- a change of 116 RPM !
A concerning 116 rpm momentary effect. (Even if it's just for one rotation until the next firing stroke.)
A definite cause for flickering lights and a distorted sine wave pattern.


Now lets look at and 1800 rpm head with the same rotational interruption (4 rpm)...

ENGINE RPM      RATIO         GEN. RPM
================================
650                       2.77                 1800
646                       2.77                 1789 <---- a change of only 11 RPM

So an 1800 rpm head has considerably less rotational interruption due to the smaller speed change ratio of the belt drive.
Hence less voltage change and less light flicker.

I would argue that a 1200 rpm (or even a 900 rpm) head would have considerably less flicker.
In the old days, there were 900 rpm generator heads.

BruceM:
I have a form of epilepsy from MS and so Listerflicker is an issue for me.  I use my Listeroid to power my shop's 2000W of heat lamps.  Before I did some work on the flicker, I could not use my shop heat lamps without health and safety problems. 

The Lister CS frequency and resulting generator head frequency variation is in itself not the big problem for lighting flicker, based on my experimentation with a custom AVR on the ST-3.

Instead it is the poor voltage regulation resulting from rpm variation; slowest speed during compression, fastest during power stroke.  With an AC voltage peak filter on a step down transformer, I was able to see this as a 5Hz hump variation visible on oscilloscope. Another forum member used it on his unit with SOM flywheels and saw a similar amplitude and frequency pattern, though without a digital oscilloscope it was very hard for him to see this 5 Hz signal representing AC peak voltage variation over time.

By messing with the RC time constant used for measuring the AC peak voltage for my custom AVR, and using mains voltage (not harmonic) to have more power during the compression stroke, I was able to match the performance of the SOM flywheels.  For 100W bulbs or bigger, that good enough for me to use.  One of the problems is that the very large inductance of the 4 rotor coils of the ST-3 causes a delay in response to changes in excitation current/voltage.  So even though excitation is cut off by my AVR during the compression stroke as voltage rises too high, it continues to rise with no further excitation added (the inductance stores and gives back the energy).  This could be electronically compensated,  by either partially shorting the excitation coils, or clipping the peaks of the AC waveform.  Both waste power, though the AC waveform peak clipping could be captured into a capacitor bank to be used for subsequent excitation.   This would be pretty complicated, and there is little market for such a sophisticated ($) AVR for very low speed engines, so I didn't try to tackle it once my own flicker reduction efforts were sufficient for my using 250W heat lamp bulbs for a few hours at a time. 

It is true that frequency variation alone might be noticeable by some, but my opinion is that mostly, it is voltage variation caused by rpm variation of the engine.  For my 650 rpm CS 6/1, the AC voltage peak has a 5 Hz hump; drops low during compression, then goes up after power stroke and sags, repeat.

While some of my older posts seem to have vanished, this old thread on the flicker issue might be helpful for newbies:
https://listerengine.com/smf/index.php?topic=2572.msg30553#msg30553

As for LED bulbs- they will be no help for flicker unless the bulb is the type with a switching AC to DC converter/regulator. Many currently made LED bulbs only rectify the AC to a small capacitor, with a linear DC current limiter, and they will flicker as bad or worse than incandescent bulbs since the LED's have no filament thermal persistence as incandescent bulbs do, increasingly for higher wattages.  You can generally confirm the presence of a SMPS type LED bulb by using an AM regenerative tuner type radio tuned between stations near the bulb on and off.  If you hear some new noises when on, yep, it's a switcher type bulb. 

Best Wishes,
Bruce

glassblower:
Very nice Build, Neat and orderly.

I'm looking to build a similar system to work with my solar panel system as well. It looks like you are using the mppt75 charge controller from you single wire alternator, is that correct? Did you install a two conductor lug on your single terminal of your alternator?  When you integrate the solar system, I assume it will have it's own charge controller tied to the same set of batteries. Which Magnum inverter did you use?

Sorry for all the questions, kept pausing the video and tried to understand how it was all wired together.

Thanks

veggie:

--- Quote from: glassblower on April 28, 2022, 06:07:12 PM ---Very nice Build, Neat and orderly.

I'm looking to build a similar system to work with my solar panel system as well. It looks like you are using the mppt75 charge controller from you single wire alternator, is that correct? Did you install a two conductor lug on your single terminal of your alternator?  When you integrate the solar system, I assume it will have it's own charge controller tied to the same set of batteries. Which Magnum inverter did you use?

Sorry for all the questions, kept pausing the video and tried to understand how it was all wired together.

Thanks

--- End quote ---

Hi,

The 50A alternator is wired directly to the batteries and the uses the voltage regulator in the alternator to control current/voltage when the engine is running.
The "Intronix Power" 25A, 24 volt solar charge controller (CC) is not connected to the alternator in any way.
Solar panels connect to the input of the CC and the the output of the CC is wired directly to the battery posts.
So, two separate charging systems connected to the same battery.

good luck with your system build,
veggie

glassblower:
Gotcha, Makes perfect sense. I like the simplicity of that design. Thanks Veggie !

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