Author Topic: tell me about the "brushless" heads  (Read 1857 times)

32 coupe

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tell me about the "brushless" heads
« on: September 14, 2017, 05:43:24 PM »
After a few bouts with storms and running a genset for quite a few hours I am considering a
brushless head.
Being "electrically challenged"  I only know I am tired of tje flickering lights. Not to say my system is
terrible, because it's not, but from what I have read the brushless heads are the way to go.

Any input ?

Gary

« Last Edit: September 14, 2017, 06:18:50 PM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
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38ac

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Re: tell ma about the "brushless" heads
« Reply #1 on: September 14, 2017, 06:00:39 PM »
Gary, I am right up there with the worst of electrically challenged but  I do know that flicker is not a generator head problem, meaning it is not created by the head. It is a mechanical problem created by the prime mover, thus the fixes are mechanical not electrical.  If anyone has successfully eliminated flicker  buy playing with the electrical end of the set I have forgotten reading about it. It canbe reduced, but not eliminated.  One of my friends has an absolutely top of the line (and very $$$) generator on a Ruston Hornsby Mark CR 17HP single cylinder diesel and flicker is so bad from that 300 RPM engine that he has all but given up on the project.  As an aside flicker affects people differently, like you it drives me nuts but the wife doesnt know what I am talking about, she doesnt even notice it.
Collector and horder of about anything diesel

32 coupe

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Re: tell ma about the "brushless" heads
« Reply #2 on: September 14, 2017, 06:18:20 PM »
I wondered about that.
I have a 3 cylinder Mitsubishi engine that I am going
to try. Thinking the 3 cylinder my run "smoother".
I will be playing with it soon and report my findings.

Thanks, Butch, your input is always appreciated !

Gary

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

Tom

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Re: tell me about the "brushless" heads
« Reply #3 on: September 14, 2017, 06:28:34 PM »
If I had to build a new system from scratch, I'd have an inverter supply all the mains power and use the Listeroid just to charge the batteries. My system is 48v and what I would do is run an STC 3 phase gen head and rectify the power into a MPPT charge controller. My reasoning on the STC gen head is that if needed 120vac can still be pulled off of each leg of it and the 3 phase power will rectify cleanly and cheaply into DC power.
Tom
2004 Ashwamegh 6/1 #217 - ST5 just over 3k hours.

BruceM

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Re: tell me about the "brushless" heads
« Reply #4 on: September 14, 2017, 09:19:47 PM »
+1 for brushless heads being of no benefit for flicker. 

I have a design for a simple AVR that does compensate for Listerflicker.  A PCB was made from version of that and offered here at one time. fine. Low wattage incandescent bulbs are still problematic for me but I don't use AC for those, I use 120VDC.

It does a better job on flicker correction when powered by the mains than the cheap China AVRs CGG is selling. 

You have to remember that an AVR connected to the harmonic windings as the excitation source can only limit the harmonic ouput. If the harmonic is barely adequate, it's output will NOT be adequate during the compression cycle, so the AVR will not be able to compensate.  The excitation source must have substantial excess power to handle this situation.

Contact me if you need the schematic or PCB layout. It is a job suited for a fairly skilled electronics technician and not a novice.


cujet

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Re: tell me about the "brushless" heads
« Reply #5 on: September 16, 2017, 01:46:34 AM »
I suppose the only real remedy is additional flywheel inertia. I'd love to reduce the flicker on my 20/2 setup. To that end, I picked up a very heavy flywheel for the generator head. Have not installed it yet. I'm thinking that even that 50 pound additional gen head flywheel won't be enough to make much difference though.

What's weird to me is that my flicker is worst on startup, and far better after a few hours run time.
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BruceM

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Re: tell me about the "brushless" heads
« Reply #6 on: September 16, 2017, 01:54:40 AM »
Sorry I missed that important observation earlier, Cujet. Does it have any adjustments?  Some AVRs do and can be tuned to better compensate for Listerflicker.  At present it may be making it worse. 


MachineNLectricMan

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Re: tell me about the "brushless" heads
« Reply #7 on: September 16, 2017, 09:41:11 AM »
I've heard of an effect known as diesel knock on cold engines where the onset of ignition is delayed, then occurs all at once causing a sudden rise in pressure. Along with this will be a sudden onset of flywheel acceleration. When the engine warms up, this knock disappears. This could make flicker worse while the engine is warming up. The electronics in any semiconductor based AVR should not have any warm up effects if designed correctly.

In my early days of electronics repair, we had tubes, they did require a warm up. Some of the mobile radios we once installed and repaired occupied the entire trunk of a car for only a hundred watts or so! Unless you have a tube AVR, it's got to be an engine effect.

dieselspanner

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Re: tell me about the "brushless" heads
« Reply #8 on: September 16, 2017, 10:50:44 AM »
I've noticed a similar effect on the 12v 'lgnition' type lamp I've installed on the supply from a small transformer.' wired into one phase, it supplies the fan.

After a while the 'flicker' is far less pronounced, the rev counter is electronic and only 'samples' once a second so that wouldn't show any pulsing, food for thought.

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

cujet

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Re: tell me about the "brushless" heads
« Reply #9 on: September 16, 2017, 01:34:06 PM »
The AVR is just the one sold at Central Georgia Generator. It's a fairly standard unit, and I do not believe it has any adjustment other than voltage. But I will double check.

I think it is the AVR115 unit he sells.
« Last Edit: September 16, 2017, 01:37:07 PM by cujet »
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glort

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Re: tell me about the "brushless" heads
« Reply #10 on: September 16, 2017, 04:10:16 PM »

I have read f people saying they put Double flywheels on their engines and it didn't help a lot which seems at odds with what one would think but maybe the extra momentum does not sufficiently account for the slowdown maybe from compression and then the acceleration from firing.

One thing I learned from mucking round from small engine DIY Dynos is weight is not as Important as Diameter.  I large circumfrence  flywheel of lighter weight has more momentum and resists speed change more than a smaller but heavier rotating mass.
It might be more benificial to have a 50" 20 Kg flywheel than a 24" 50Kg flywheel.
I'm sure there are formulas that could be looked up to work it out.

One way to avoid flicker is to convert the power.
I have put Car alternators on my roid feeding a 12 or 24V battery setup and run an inverter from that. Smooths the power perfectly as the battery filters out and clamps any fluctuation... not that I have seem much 

I Also used Computer UPS units. Can be had relatively cheap if the battery's are stuffed. I wired the battery leads to car battery leads and wired the terminals, alt outputs and UPS leads all together.  Worked perfect and the output was perfectly stable as is the job of those units in the first place.
The ones you want for this idealy are the ones that will " Self Start", ie, will fire up when connected to battery power only and don't need mains power to fire up. These tend to be the double conversion units which are essentially a battery charger and inverter in one.  The AC is refctified to DC and fed to the battery. The DC from the battery is then inverted to AC again. 

Makes the units output very stable and tolerant of a wide range of  AC problems because they basically ignore the AC and create output from the DC/ battery side.

APC UPS units up to the 3Kw units I have played with are all 24V. Another brand ( black colour, forget the name) are 96V in the higher outputs which isn't nearly as useful for generator application.

BruceM

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Re: tell me about the "brushless" heads
« Reply #11 on: September 16, 2017, 09:06:10 PM »
Good theory, MNLM.

Caps and resistors do drift in value with heat, so some analog timing circuits do change slightly with temperature.  Many better ($300+)  AVR designs will have separate fast and slow response stability/damping circuits that are RC based and thus could drift with temperature if badly designed; but I like any other theory better that would provide an explanation for a meaningful change in engine deceleration/acceleration profile despite identical average RPM.  There is a sharp drop off of speed during compression, though one would think that would get worse when hot; perhaps it's the ignition event and acceleration. 

 I'd love to see data on a rubber wheel type tachometer showing rpm profile hot and cold!







 




starfire

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Re: tell me about the "brushless" heads
« Reply #12 on: September 17, 2017, 01:41:42 AM »
Perhaps we could add a psuedo electronics and AVR section to this forum?

 In pre electronic times, like 200 years ago when I was a boy, voltage regulation was done passively, and did work rather well. I remember the old Westinghouse, Vickers, Markon stuff that wouldnt know what a transistor or SCR was, yet they ran well and maintained pretty good regulation and certainly didnt flicker.

Easier than messing  with heavy flywheels, try this.
Magnetic amplifiers were common back then, although they were not recognised as such at the time.
Its easy to make one.
take a common isolation transformer.
Short circuit the output terminals, or the input, it wont matter.
The other two unshorted terminals are connected in series with the generator load , ie the IT live goes to the live of the generator, the neutral to the lights/house.
What this does is place a current sensitive variable  inductance in series with the output generator current, the current increases as the voltage increases on each mains cycle, therefore filtering occurs on a cycle by cycle basis , much more accurate and quicker than can be achieved by varying exciter current alone.
 A transformer "reflects"  the impedance from the primary into the secondary, therefore with light loads, the transformer will have a higher series AC impedance than with heavy loads ,this is dependent on your particular  core saturation curve, reluctance and other boring stuff
Given the random nature of your transformer and generator combo, this may  work well or provide no change at all., but is just minutes to try.
 Ideally, custom inductors are required, but luck can happen with commonly available items.
I am assuming those with the nounce to be messing with this stuff also know to be safe.
To have this work well, a low value high current wire wound type adjustable resistance load should replace the transformer short, and then adjusted for best performance. These will commonly  be in around the 5 to 25 ohm range allowing the core saturation level to be adjusted
This method  can remove all high frequency flicker and tidy up shitty waveforms. when set up correctly
The transformer VA rating needs to be at least equal to the average generator load, err on the heavy side, if unsure, watch the temperature rise, warm is ok..
« Last Edit: September 17, 2017, 03:57:15 AM by starfire »

Barenburg

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Re: tell me about the "brushless" heads
« Reply #13 on: October 08, 2018, 07:10:29 PM »
Has anyone tried the Isolation Transformer trick?

BruceM

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Re: tell me about the "brushless" heads
« Reply #14 on: October 09, 2018, 12:40:30 AM »
The transformer "trick" Starfire suggested does not work. 

Not even a regulating transformer (operating at saturation) works; I tried that many years ago. They just aren't designed for coping with the frequency variation along with voltage regulation.

A very responsive AVR will help, better if run off the mains or a transformer with LOTS of extra capacity.  Based on AC electronic measurements using a low pass filter an SOM flywheel 6/1 provided about the same reduction as my AVR on a std. My Rajkot spoked wheel ST-3.

I could never live in a house with 60 watt incandescents on an SOM; that is too much flicker for me.  At 100 watts it is bearable for a short time but is bothesome. At 250 watts (my heat lamps in the shop) it is acceptable for 4 hrs of use.
Higher wattage bulbs have less flicker due to thermal mass of the thicker element.

Screw the inverter, 120VDC is the way to go.  Zero conversion/standby loss, and 90% of all switching power supplies won't complain a bit.

I only turn on my inverter for running the well pump or washer, everything else is run on 120VDC.