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Author Topic: I'm ready to buy a gen head..............  (Read 647 times)

Brad Silwood

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I'm ready to buy a gen head..............
« on: March 31, 2021, 04:59:17 AM »
......... for my Lovson 6/1 CS. I wish I had had enough foresight, to have gotten an Utterpower PMG years ago. I've been doing a bunch of searching the brands, and reading through years of posts. Have looked from the Chinese ST's, to Northern tools brushless, Stamfords, an on and on. I even spoke to a fella that would make me a custom head. One of the brands doesn't make below 8kw, and I imagine 5kw is probably max for my single. So, I'd like yalls opinions please. Who's had good service with what ?

If I wanted a brushless unit, with clean power out, didn't want to buy Chinese, now that I'm thoroughly confused - is there such an animal

Thanks,
Brad

« Last Edit: March 31, 2021, 05:39:48 AM by Brad Silwood »
Lovson 6/1, 23.5 " spoke style flywheels, has not run yet
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dieselgman

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Re: I'm ready to buy a gen head..............
« Reply #1 on: March 31, 2021, 05:07:06 AM »
Stamford original or Chinese Stamford copy - very close to the same thing. Stamford original 8.2kW about double the cost of the Chinese clone. Lister/Petter  had Chinese manufacturers building most of their (rebranded) generator heads for the past decade. We stock a wide array of these machines.

There is no real penalty in running an 8kW head at 1/2 its rated output... so that is a non-issue.

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cujet

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Re: I'm ready to buy a gen head..............
« Reply #2 on: April 26, 2021, 01:28:34 PM »
I have 2 ST heads. The 6-1 has a ST-8 and the 20-2 has an ST-15. Both of mine are relatively low quality units and produced a less than ideal sine wave and unsteady voltage. They also required/require bearing changes to higher quality ball bearings. I've taken some steps to improve the sine wave and regulation by adding an aftermarket voltage regulator and picking up the regulation current from the main winding and not the Z winding on my ST-15 (as the Z winding was unable to get the voltage high enough, it was 219 max and dropped to 209 under load). With these mods, my ST heads are capable of producing high enough quality power. Even the oscilloscope sine wave tracing looks pretty good.

However, the main issue I have is related to the power pulses of the Listeroid engines. Each time the engine has a power-stroke, the gen head speeds up a touch. This leads to flickering light bulbs and complaining UPS power supplies. As you might expect, a few items in the house, like the microwave, simply won't work. Not really a big deal, as I can power that with my Honda EU2000i.

I'm not sure the choice of a 3600 RPM head would fully solve any problems, but it would allow one to install a more effective heavy pulley/flywheel on the gen head as the higher 3600 RPM speed (vs the 1800 of the ST head) has much more inertia. Might smooth out the power pulses a bit more. But it's just a guess as to how much improvement there would be.

If I were to do it again, I'd choose a higher quality generator head and I might experiment with a 3600RPM head.

In any case, the gensets have seen heavy duty post-hurricane use. Both worked well for extended periods of time and the relatively minor power quality issues were not terribly hard to deal with.
« Last Edit: April 26, 2021, 01:33:57 PM by cujet »
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BruceM

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Re: I'm ready to buy a gen head..............
« Reply #3 on: April 26, 2021, 06:30:52 PM »
Hey Cujet, I concur with your assessment.  After being inside handful of ST heads, I don't recommend them.  Mine is working OK, but even my backup unit ended up having serious problems, beyond bearings and rectifiers.  Some are pretty good and/or can be made so by an AVR on the mains (to avoid many of the Z winding issues), but it's more work than the cost savings are worth.  I'd rather have a 3600 rpm head than mess with another ST.

I believe the problem with your microwave oven is the cheap AVR you have;  it is NOT regulating to RMS voltage, which a well functioning Z winding does fairly well.  This affects a large, low power factor load like a microwave and will result in low voltage.  I ran into this the hard way, of course.  I have the ability to switch out my AVR and go back to the direct harmonic excitation with dropping resistor, and that's how I deal with that kind of loads (like a friend's small MIG welder running on low amperage setting).   

Brad-
The folks who have followed Gary's advice and gone with the Stamford have reported nothing but easy, trouble free operation.  I highly recommend DES.  No marketing/promotional bullshit (I have a severe allergy to it), incredible depth of knowledge and 1st rate support.

On flicker, the best you can do is  heavy flywheels plus a small brushed head with a fast AVR off of mains to compensate for the rpm/voltage sag of compression stroke and voltage rise on power stroke.  Larger heads can't be compensated as well electronically due to much larger rotor inductance and the resulting lag in response.
Lister put a flywheel on the SOM generator and big flywheels for good reason.  I have measured the reduction in flicker on my custom AVR versus  another forum members's SOM flywheel 6/1 who I sent my measurment/filter circuit. They both provide about the same reduction.  I found that improvement is just enough to allow me to use the 8-250 watt heat lamps in my shop; 60 watt incandescent bulbs are unbearable.  LED bulbs which have a switch mode power supply, regulating the LED current will not have problems with Listerflicker.  They do generate significant power line EMI but that's your trade off.  So listerflicker can be avoided as an issue if you are careful about LED bulb/lamp selection.

Best Wishes,
Bruce







32 coupe

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Re: I'm ready to buy a gen head..............
« Reply #4 on: April 27, 2021, 12:46:11 AM »
I have 3 ST heads and 2 Stanford clone heads.

2 of the ST heads are very well behaved units. No AVR's on them and they
maintain voltage and hz under a heavy load. I don't have a scope so I don't
know what the waveform looks like but it runs everything in the house and shop
with no problems. They were purchased 12 years ago or there abouts.

The 3rd ST head does produce power but its really just a heavy paperweight.
An imbalanced load will set the thing into an animal like screech from hell.
Without the AVR it will put out a respectable 320 volts or so.  It is probibly 2 or 3 years old.

The 2 Stamford clone heads are rock solid. Great under load with practically no voltage or hz
drift. They are 2 or 3 years old.

The only thing I did discover with the clone heads are that the metal mounting bracket is rather flimsy.
My small mitsubishi set up with the lovejoy coupler direct drive system would vibrate the gen head enough
to destroy the rubber spyder. I added a brace from the engine to the top of the gen head and that cured that
problem.

My other clone is run with a serpentine belt/pulley and a Listeroid. I haven't run it enough to really know what it's what because
the problem with the gen head bracket flexing wasn't discovered untill after the serpentine setup was test run
then set aside. 

So with that said the only way I would buy another ST would be if I could run and inspect it. Run under
load and inspect for copper wire and better bearings.

The clones cost about 2x the ST heads. Why deal with the head ache especially if you want to have
a system that is reliable. The question is do you NEED a generator. And what do you want to do with it.

I have several generators including military sets. I have had the luxury of "playing" with the Listeroids and
ST and Stamford clone gen heads. Different belt drive setups and types.

When I need a generator I pull out the Changfa direct drive with a 15 kw ST head or a military unit.

Buy the Stamford clone and you can sleep at night without worrying about the ChiCom ST generator letting
out the magic smoke. The Stamford  clone is ChiCom as well but MUCH better quality.

Enjoy,
Gary



« Last Edit: April 27, 2021, 01:11:55 AM by 32 coupe »
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cujet

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Re: I'm ready to buy a gen head..............
« Reply #5 on: April 27, 2021, 10:32:15 PM »

I believe the problem with your microwave oven is the cheap AVR you have;  it is NOT regulating to RMS voltage, which a well functioning Z winding does fairly well.   


Well, the AVR was not that cheap....  ;D it's not the original, but an aftermarket one from Central Georgia Generator. It's able to keep the voltage much more steady and does help reduce flicker. I also have a bank of capacitors in the field circuit to smooth out the power.

Whether it's a properly made, quality AVR is difficult for me to assess. I will say that voltage remains at 120 per leg. The Z winding was/is wildly insufficient on my ST head and provided unacceptable performance.
« Last Edit: April 28, 2021, 03:13:10 AM by cujet »
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BruceM

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Re: I'm ready to buy a gen head..............
« Reply #6 on: April 28, 2021, 03:39:08 PM »
Hi Cujet,
CGG was selling cheapo AVRs, cheapo bearings hardly better than the orginals, and low quality ST heads where the harmonic windings are so far off (high) that an AVR must be used.  My backup ST-3 has harmonic windings so low in output that AVR off the mains is required, plus other serious mechanical issues. (My ST-3s are not from CGG, the problems are in China, and CGG does try to make good.)  My neighbor got an aluminum rotor winding ST-3 (that failed) from CGG also.  You can get the same AVR's direct from China for under $50 each. They have a modest service life, a few years. 

They do not regulate to RMS voltage, and that explains your microwave oven (typically a large, low power factor load) issue pretty well.  One issue I found is that the analog RMS IC's have so much delay that it blows the flicker compensation.  I tried to add that to my custom AVR to handle large low PF loads, but then found my shop heat lamps were unbearable, so reverted to the simple RC filtered semi-peak voltage regulation.