ST Head Waveform Regulation

[WStayton]

Ok, I heard back from Tom Osborne, along with his permission to display the message or parts thereof, here.

First, what I asked, having chopped off all the description of what I am planning, since you already know that:

>1) First, I am concerned about the wave form on the output of the ST Generator
> Head, as delivered, no chages to the internal regulator. From your experience,
> just how dirty is the output and would it likely interfere in normal household
> loads like a computer or a tv w/ a satellite receiver, microwave, etc.
>
> 2) If the output is, indeed, unsuitable or even marginal for these type uses,
> how is the output if the AVR-type regulator that you also sell? Would it then
> be acceptable for the uses described above.
>
> I have seen an o'scope trace of the output of one of the other member's of
> Microcogen with your AVR on an ST head as delived from your shop and that
> apeared to be very clean, though that was a three phase head, so I'm not sure
> that I should automatically expect the same result on a single phase head.
>
> 3) Also, besides the wave form, how is the voltage vs load with the AVR
> regulator vs the straight Z winding fed output withouot the AVR unit?
>
> 4) Are the bearings in the two bearing head as delivered from China, generally
> lower quality than would be available here? I am inclinded to change them
> right "out of the box" if they come from China, but I am interested in hearing
> your opinion of them.
>
> 5) No matter how the head is equipped, with regard to the circuit feeding the
> windings, I figure that in an emergency, I could always feed straight DC from
> my battery bank to the brushes of the field coils of the generator to get
> electricity if all else fails, What is your opinion of this emergency-only
> procedure. Obviously I would "fish" around to determin what DC voltage gave me
> an acceptable output voltage, starting with 36 volts and increasing by 2 volt
> steps (one cell's worth) until I got something that I could live with - I would
> think that such a fishing expedition shouldbe conducted in advance so I woulod
> know what voltage to use if it was needed and could just hook it up if
> necessary
> and required.
>
> 6) How many hours do you feel tha one should plan on getting out of one set of
> brushes for this 24 kW generator-head.
>
>
> 7) Are their any spare parts that you would recommend, in addition to an extra
> set of brushes?
>
> Do you see any problem using the Lovejoy type coupling that you sell to hook
> the generator to the output of my automotive transmission? I had thought that
> it might be nice to try and figure out where the peak loads were coming from
> the generator (4 per revolution) and then set it up so so that they didn't
> coincide with the torque peak from the engine, but I have no idea of how to
> identify where the peaks from the generator occur! <grin>
>

To these questions, Mr. Osborne replied as follows:

>The ST generators is a good generator for backup or prime power >as long as you understand a few things about generators.
>This unit does have a little trash on the sine wave that come from >running brushes.

>There is also brush maintenance that must be done. They will last >from 900 hours to 3700 depending on how you keep the aligned >on the slip ring. The ST is inexpensive so it makes them  popular >with the DIY people.

>The best quality, if you do not want to do any maintenance, is >the Stamford brushless type. The waveform is very clean and >stable
>It has a SX460 or AS440 AVR that comes with this unit.

>Will try and answer your questions in the order you asked them.
>1) On the engine, make sure you use a good governor, mechanical >or electronic. Will need to maintain the gen head at 1800 rpm + - >60 rpm. This is 62hz to 58hz

>2)Would recommend an AVR for all your electronics even though i >have used them for all my electronics without an AVR( George at >Utterpower does not recommend the AVR)  www.utterpower.com >I just like the steady voltage. Remember, a steady voltage will >not make up for a varying rpm (frequency) Rpm must be regulated >(governed ) first

>3) Some people like doing away with the harmonic winding, do not >know exactly the reason.

>4) The bearings are sealed on the units we have. They will last >10,000 hours so would not be concerned about bearing at this >time.
>Use them until you hear a noise then change.

>5) The loveJoy coupling will be fine, just make sure the engine >and gen are mounted solid to the same frame, (no rubber shock >mounts) and then shock mount the frame if you like.

>6) Do not know how to figure peak loads coming from the gen >head.  Do know you need to check carefully the harmonic >vibrations
>Do a good search on the harmonic vibrations in diesel generator >sets  http://www.deicon.com/technote/>diesel_gen_tuned_vib_abs.pdf
>Small units like this is not as much a problem as larger units.

  Read it and tell me what you think!

Regardz,

Wayne Stayton

[mike90045]

I think an 8 bit analog handheld .

There is digital, where bit count= resolution, and there is Analog.   Anyone trying to sell you 8 bit analog, I'd be wary of .

[rcavictim]

I think an 8 bit analog handheld .

There is digital, where bit count= resolution, and there is Analog.   Anyone trying to sell you 8 bit analog, I'd be wary of .

Could be the price.  two bits = 25 cents.  8 bits = a dollar.

8 bit resolution refers to binary numbers (digital is only ones and zeros) meaning the scale is divided into 256 discrete steps.  That is not very good resolution.

[Shipo]

I had  the same concern when I'm on generator, how safe are the power on the sensible equipment. The best idea is to have all those equipment on a UPS.

[mbryner]

Or run all gen head output through charge controller first.   Then the only thing that gets to the house is perfect sine wave from the inverter.

[Ronmar]

My ST-5 output is not that bad.  I have compared it to generators I work with using an O-scope, and it is comparable with perhaps a little brush noise, and some slot noise as the ST rotors are not skewed.  I am also not running mine at maximun output(not enough engine:() so the Z winding effects may not be as pronounced at those lower loads.  Good simple backup power, I am happy with

Most electronics should not have a problem, as they are taking the AC line voltage and converting it to DC via a switching power supply anyway.  That power supply has a very large input voltage range, and can take in some real crap and make DC out of it:) 

[mbryner]

Completely in agreement w/ Ronmar.   The only problem I ever had w/ the ST head was flickering fluorescent light bulbs, probably because of the pulsed output from the slow speed engine's power strokes.  Anything that ultimately uses DC shouldn't care.   Are there any specific devices, Wayne (original poster), that you are worried about?

[Tom Reed]

After living for 3 years with our ST5 the only item in the house that has an issue with the output is our dishwasher. It seems to be very sensitive to over voltage at around 126 volts. It works fine while bulk charging, but as we reach the end of the absorption cycle it tends to shut it's self down. We have all the other common household stuff and as a software developer I'm on the computer a lot of the time while it's running and no problems. Fortunately we've had no appliance failures either.  Our ST5 is a straight Z winding non-AVR unit.   

[Ronmar]

My dishwasher works just fine on ST power, well at least as fine as she does on commercial power.  She being a teenager can be a little difficult to get to do her chores regardless of the power feeding the house:)

Actually I don't try and run my electric dishwasher on the generator.  My power study showed It's internal water heating elements are a rather large single leg/120V load... 

[WStayton]

to mbryner:

  I'm most worried about a desk computer (no name - built by me with a basket-full of cheap parts) and television via satellite receiver.

  However, I my have made a mountain out of a mole hill, here, since I'm planning on running the generator only about 6 hours a day twice a week for 20 weeks out of the year and then 6 hours a day once a week for ten weeks out of the year - this would be only for supplemental power when the solar panels wouldn't keep up due to length of day, cloudy weather limitations.

  Maybe I'm doing a truck load of worring about a small-basket sized problem?

  Current plan, FWIW is to use a 24 kW ST head with the AVR controller plugged by Tom Osborne, though I didn't feel that his response to my query really answered some (most?) of my questions - I may go back for a second dip on a couple of them! <grin>

[Tom Reed]

We've got satellite internet and TV, no issues there either. Even with infamous Listeroid flicker. 

[sailawayrb]

I reckon I have run just everything possible that can consume electric on my ST5 without any AVR.  I have not experienced any issues other than the microwave appears to be noisier.  I have also not noticed any flickering lights either (incandescent or fluorescent).  Perhaps using a resilient engine mount provides sufficient damping of the 5.4 power stroke to keep a significant portion from getting to ST.

Bob B.

[Ronmar]

Bob B,   Without an AVR, I don't see how you could possibly not notice the flicker.  All single cylinder gensets have it.  The most resilient engine mount in the world will do absolutely nothing for the crankshaft/rotor deceleration on the compression stroke, and the acceleration on the power stroke...  I use mostly CFL's, so don't hardly see it when on generator power, but the incandescents and a few of my shop florescents show it...  Since the harmonically excited ST heads output voltage is RPM dependent, these accelerations and decelerations make the voltage change that really make the flicker "Pop".  An AVR really takes the edge off of the flicker by stabelizing the voltage during these accelerations and decelerations...

Like Tom, I run sat receiver, flat panel TV and computers without any issues.  All these modern devices have switching power supplies with a very wide tollerance.  In fact, most modern equipment is built for the world market, with one power supply able to handle UK/European 220 power at 50HZ all the way down to 120V US domestic at 60HZ, with only a plug change, or use of an adapter plug at the receptical...  The only thing that really effects them are extreme low voltages(brownout), where they basically herniate themselves trying to hold up their end of the log and deliver their rated output from the greatly diminished input.

I have UPS's on these systems to mainly protect from brownout conditions, but they are small switching type UPS's so if the input is acceptable(between 107 and 127V), they are passing it right thru to the output, or they are online, draining battery and beeping every minute:)  When I loose power on an evening, I can be up on generator power, without the wife or kids ever stopping the watching of the tv show that is on:)  The UPS fills in the 10 minutes or so of power gap... 

[sailawayrb]

I would certainly agree that one can feed PCs practically pure noise and they will digest it perfectly fine given that they are DC devices with robust power supplies.  I think I have in excess of 15 homebuilt PCs operation at our place for various purposes (and some are used for high end gaming, high end engineering analysis, and home automation) and we have never experienced a single hiccup while on ST power.  The only device I have any concern running on ST power has been our microwave, which actually sounds different when being feed ST power...but nevertheless works well and hasn't had a problem either.

I would agree that if the infamous Lister/ST flicker is purely due to the piston velocity change during the power stroke, in theory this should be unaffected by the method of engine mounting as the piston is indeed hard linked to the flywheel, which is also essentially hard linked to ST (if one assumes a serpentine belt provides hard linkage).  However, the forces that create piston velocity also react (equal and opposite) with the engine crankcase and hence the engine mount, which can then ultimately react with the piston (both fundamentally and via harmonic structural bending modes).

Ability to perceive light flicker does vary significantly for different people too.  I think the generally accepted average threshold of perceiving light flicker is about 50 Hz (i.e., if a light goes ON and OFF less than 50 times per second, it becomes perceptible to the average population).  For our US 60 Hz power, an incandescent light flickers at 120 Hz (i.e., the light goes ON and OFF 120 times per second).  The older florescent lights with magnetic ballasts flicker at 120 Hz as well.  The newer florescent lights that have electronic ballasts flicker in excess of 20,000 Hz.  No one in my family has noticed any flicker on our old tube fluorescents, new compact fluorescents, or incandescent lights.  The only thing visibly noticeable is the brief transient when toggling from live grid to live generator via the transfer switch.

Bob B.

[sailawayrb]

I should also mention that my ST is wired for 120VAC, so my electrical loads are ALWAYS balanced and my ST doesn't exhibit any "growling" or other associated unsteady ST dynamics issues. Our house power requirements range from about 1500 to 2500 watts, so well below 6/1 and ST5 limits.  I also use George's engine throttle linkage mod to minimize the RPM variation resulting from our relatively small electrical load variations. Per Kilowatt monitor, my maximum voltage variation is less than plus/minus 3 VAC from my nominal 122 VAC. Frequency variation is within plus/minus 1 HZ from my nominal 60 HZ. If I had a light flicker issue, I think I would consider designing/constructing a low bandpass filter with a cutoff frequency around 25 Hz in lieu of using an AVR.

Bob B.