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More on Voltage Regulators (AVRs) EARN $100 CASH! Here's my offer, if you have a 'flicker problem', AND you buy one of the AVRs mentioned below, AND you can prove with scope traces that there is a discernible difference in the wave form where the human eye can perceive a definite improvement, AND the EEs who frequent here accept the results, then Utterpower will send you $100, AND give your Voltage Regulator coverage here, including a link to your sales site! In order to build some background for readers who haven't followed this, let me tell you what I think causes flicker, there is a lot of stuff out there to read, one person in our DIYer community even wrote it was the ST generator causing it :-) Here's how I have come to see it AFTER studying it, and leaning from EEs I trust. Diesels have rather strong power strokes, this shows up as a less than constant rotational speed of the crankshaft. The human eye does have some retentive powers, and at 60Hz or so, it is difficult or impossible for the average human to see a flicker WHEN peak voltages are constant. However, the human eye is very good at distinguishing a peak voltage that is different than the one prior or after it. What the eye locks onto are the >peaks< associated with each power stroke, and they are infrequent enough where the retentive powers of the eye can not MASK the events, you might see these at a rate of 15 events per second (example). The question we need ask, can this VR circuit (offered for sale) mentioned below actually do what the person who sells it says it can, or is this just more snake oil? Can we use this as a leaning experience here at Utterpower? ---------------------------------------------------------------- Here’s the post that inspired this page… the following was posted in a public forum, another EE saw it, and sent it.. ( I say that because the Author professes to be an EE according to my readers). From:
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George Comment: As per the mention of flicker reduction, “quite a bit” is not a term that EE’s I know and trust use. It is however a common term Salesmen use, we ask ourselves, is there something being sold here? How hard would it have been to put the scope on the wave form and actually measure the reduction? If there was strong evidence the reduction was there, wouldn’t you measure it and report it? Ever met an EE who didn’t own a scope or have access to one? Following is more input about AVRs.. this is my opinion, but it has been honed with years of reports from the field and repair facilities. An expensive voltage regulator custom built for a gen head is a good thing, especially if there is a limiter for field current, and it has been tuned for the gen head you deploy it on. Still, the vast majority of generators sold do not have VRs, the ones that do are poorly implemented and are the number one cause of failure. A good one is often more expensive than the generator head itself. With input from a lot of people, I think I have the messages on Utterpower pages just about right. If you come across anything that needs work, let me know. A high percentage of PMG buyers have lost generators when they thought they needed it most. All of them had the failure happen on the Gen head side as opposed to the prime mover side. Some did take the set to a repair facility and found exactly what I had shared on my pages, repair too expensive because of the cost of the electronic repair parts.. What I find most entertaining here is the fact that it’s a person selling the AVR that reports they’re good, what a surprise. Certainly that can be said about me as a counter I guess, (Utterpower doesn’t like them because he doesn’t have mine), (fact is, I was later reminded he did offer to supply his AVR to utterpower). There’s nothing wrong with an AVR except the really good and reliable ones are usually built specifically for the Gen Head deployed. They are normally found on expensive Gen Sets, sets beyond what DIYers are normally willing to pay. Anyone who knows how production lines work learns quickly, making AVRs 1000 or 10,000 at a time is what you must do, cost per unit plunges. Manufacturers often use statistical data to carry them past the warranty period, parts they stock after that get marked up as the number in inventory falls, these are where the ridiculous prices your are quoted come from, they have darned few on the shelf, and they can say they have the parts as opposed to having someone say they didn’t support what they sold. There’s always the other option, the supplier of the AVR will do a short run of spares for 10 to 100 times the price of the original production run. This is what Generator manufacturers attempt to avoid, there is also a lot of expense in warehousing spares for discontinued product. I remember we once designed a power supply with a certain FET, we bought 6000 of them for pennies each, when we went back looking for the same part, we couldn’t find them. The cost to fire up the production line and have this specific FET made was pretty high per our measure. Look at FETs sometime, it’ll boggle your mind how unique a FET can be, and how specific the needs of your designed power supply is to the FET you need. Designers and manufacturers learn quickly what burns them. The point is, after your generator gets a few years under it's belt, that marginally designed AVR could be raising the current well beyond what the field was designed for. Sometimes, it just heats the insulation varnish a little too much, it gets brittle, the thermal expansion, the vibration work on it over time, and then the falure shows up as a shorted field. A diagnosis of the root cause may be missed. If you're really unlucky, maybe the rewind shop would rewind the rotor, and set up up to fry a second field winding? Lucky you! The other possibility is you bought a higher end generator with a better AVR, as it gets older, the AVR may get fairly expensive to replace (they often do). This is where folks go a little crazy when they get a quote of twice what they paid for a used generator to replace the AVR. A good AVR is Good, A generator that uses an AVR is not likely to work after an EMP attack. A generator that doesn’t have an AVR will not fail for the number one reason generators fail "AVR failed" there's nothing to add other than the obvious, if it isn't part of the design, it won't fail. AVR are often deployed because the governor is inadequate, why not work on that instead? More to think about: There are all kinds of ways to regulate voltage, possibly the worst ever was what we saw in British Motorcycles (and Others) in the sixties, and simple Zener and resistor that put what looked like a crowbar across the output of the generator when the voltage was near hot enough to blow out the taillight. These units were finned and found mounted on the frame somewhere, and quite expensive to replace, I think is was partly responsible for building the Lucas reputation, Lucas= “The Prince of Darkness” I remember a few cheaper TV sets, looking at the way they regulated voltage was to use a zener and a resistor to create a voltage drop, the set used a lot more energy, and the heat and current often caused a diode to fail. You took this set in for repair, they charged you $125 to replace the diode and you might be good for another year. Other sets used more refined and expensive methods of voltage regulation and didn’t fail. A TV repairman of the day might whip open a few schematics and show you the difference. At the end of the day, if you want an AVR, learn the difference between a good one and a bad one. Do not get one that will drive the current in the field so high it will damage the field! This is a VERY typical report here. In addition, if someone tells you it will even partially eliminate flick, ask him if he has some scope traces that shows the difference? For those who want the most rugged and reliable set, I suggest you invest in the governor and the controls there, a lazy governor is one of the reasons AVRs are deployed, low mass flywheels aggravate the problem. All the best, George B. Additions to this page: Where VRs are discussed: http://www.utterpower.com/ST.htm http://www.utterpower.com/pmg.htm Input from Community on the public post above: Quote from PE: The more I learned about my AVR, the more I liked the standard harmonic excitation. It's simple and reliable, and it won't damage the field. My AVR is now the backup unit on the ST12 Quote from EE Here's what I've decided on AVRs. To get all the features we're looking for, in a unit designed to drive a main field directly, it would likely retail for at least $300, and perhaps a good bit more. Most DIYers would be better off spending their time and money on a good governor. The harmonic excitation system works extremely well if you can hold the speed constant. One more quote: “Quite a Bit of flicker reduction” Those of us who have studied this; we know that’s impossible. A reply post: How was the reduction in flicker measured, and how much was it? An EE would hang his head in shame knowing he had been hung out to dry. Another Quote: “I think this guy is taking shots at Utterpower because this same guy offered to supply George with his product and George refused to buy them.” ---- The above is a little embarrassing because I had forgot all about the email and the offer to supply Utterpower with these AVRs, but it is fact :-) So in the end, do your own thinking, and always read between the lines, remember, there's a language appropriate for Cooks, a 'pinch' of this, and a 'sprinkle' of that, but in our world, reporting what you actually measured is what you need to do in the DIYer community, we are generally older folks who have learned to read between the lines. Give us the facts, and let us decide. George B
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