Author Topic: brushless?  (Read 1865 times)

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quidam

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brushless?
« on: April 14, 2009, 04:27:27 PM »
first posting, so bear with me.  it seems to me that with alternators that utilize magnets there are significant problems with the stall speeds.  why not use a brushless configuration with an AVR (automatic voltage regulator)?  wouldnt this allow you to capture lesser loading at lower speeds and greater control of power generation under overspeed conditions?  couldnt this be done with a LARGE number of poles and generate very high voltages at lower rpms. battery chargers could trickle charge at low speeds and cut in more current as it becomes available.
« Last Edit: April 14, 2009, 04:27:27 PM by (unknown) »

TomW

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Re: brushless?
« Reply #1 on: April 14, 2009, 10:39:43 AM »
guidam;


You are new so I will simply suggest that you do some reading before solving problems that do not exist.


And make 2 fairly important points you seem to have either missed or chosen to ignore.


Most alternators discussed here do not have brushes.


Battery charging is a unique power production paradigm and often not covered adequately in a University education.


Just the first points I would make.


Tom

« Last Edit: April 14, 2009, 10:39:43 AM by TomW »

ghurd

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Re: brushless?
« Reply #2 on: April 14, 2009, 12:03:15 PM »
Problems with stall.  Depends on where you read.  Some other forums have problems getting up to charging voltages.


AVR, as I think you mean it, is fairly useless with wind.

I have a feeling you need to know the term "MPPT".  It may be what you are thinking about.


Brushless high voltage at low RPM is easy.  Can do it with 2 poles.  Happens too often for me.

G-

« Last Edit: April 14, 2009, 12:03:15 PM by ghurd »
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quidam

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Re: brushless?
« Reply #3 on: April 14, 2009, 02:44:00 PM »
thanks for the fast comment ghurd. some quick lookups lead me to think that the MPPT isn't quite what I meant but comes  close.  I was asking if  replacing the magnets with coils and using a seperate exciter circuit would allow you to limit the mechanical load  on the blade by controling the field strength externally and allow for generation of power at less than optimal speed. it also seems clear that I need to do some research on battery charging.  that said integrating an MPPT would seem to be indicated in this type of configuration.
« Last Edit: April 14, 2009, 02:44:00 PM by quidam »

ghurd

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Re: brushless?
« Reply #4 on: April 14, 2009, 03:47:28 PM »
Then you must be thinking of using something close to a car alternator.  

Not good.  Nothing anywhere near efficient.  Not controllable.

G-
« Last Edit: April 14, 2009, 03:47:28 PM by ghurd »
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quidam

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Re: brushless?
« Reply #5 on: April 14, 2009, 04:09:35 PM »
similar in components I suppose.  multiple stators/rotors, external exciter field etc. but auto alternators are designed to run at too high an rpm.  not well adapted to this application.  also not interested in anything requiring brushes. I am also steering away from anything requiring a mechanical linkage (belts,chains etc)
« Last Edit: April 14, 2009, 04:09:35 PM by quidam »

Bruce S

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Re: brushless?
« Reply #6 on: April 16, 2009, 09:25:14 AM »
As others have said , many have gone away from brushes a long while back.

There are still unit out there that work and have brushes, and they work for years without brush replacement, then when they wear out swap,swap, done put it up for another xx of years work..


The exciter circuit would be interesting to see.


Being that it would be AC you could build up a unit that is a step-up xformer, but the one big draw-back is that IF for whatever reason you run out of the ability to produce that first AC portion to excite the other field, then you may be out of luck.

Magnets last a long time even if you don't take care of them and simply turning a mag around a bundle of coil will get you "something" useful without anything else.

Keeping the number of items down to a minimum for a needed circuit is usually the most efficent way to go. The 'ole K.I.S. route.


If you have a design in mind draw us up one and let's see it.


Cheers

Bruce S


 

« Last Edit: April 16, 2009, 09:25:14 AM by Bruce S »
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hiker

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Re: brushless?
« Reply #7 on: April 17, 2009, 06:27:52 PM »
good read--old windchargers--with brushes....


The PLOWBOY INTERVIEW


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More Uncategorized from Mother Earth Living On June 2nd and 3rd, 1973 a Wind Energy Conversion Workshop was held in Washington, D.C. The gathering was sponsored by the National Science Foundation and implemented by the National Aeronautics and Space Administration.


Well sir...conferences and symposiums and workshops and all the other fancy meetings held to "study" a problem are all right, I suppose. But a fellow sometimes wonders if they're worth the trouble it takes to organize them.


This particular assembly was no exception. For, we're told, after nearly twó days of absorbing reports and addresses from people who've experimented with and used wind power...many of the "experts" and "engineers" there still didn't have what you could call a grasp of the energysource's potential. "You mean you really run all your lights and appliances and a typewriter and stereo and TV on electricity produced by a windplant? You mean you're doing that right now?" one incredulous engineer asked Henry Clews .


"I mean, if this thing actually works we should find out if it's practical enough to put into production. "


It was then that an authoritative-looking 70-year-old gentleman rose to his feet in the audience and said, in effect: "Why, you young whippersnapper. You're trying to reinvent the wheel. Not only will windplants work...not only can they be put into production...and not only can they be manufactured and sold profitably...but I personally built and marketed approximately 50 million dollars worth of the units from the early 30's to the mid-50's. We were already in full swing before you were born. "


Now I hasten to add that genial, polite Marcellus Jacobs didn't address the young and well-meaning (but somewhat ignorant) engineer quite so abruptly. Mr. Jacobs did, however, leave no doubt that windplants could be made to work. And he should know: Marcellus Jacobs is the man who almost singlehandedly invented the first practical wind-powered electrical generating system. He's the man who originated nearly all the noteworthy advances in the field from 1930 to 1956. And he's the man who dominated this specialized mini-industry until the day he decided to move on to other interests.


Marcellus Jacobs hasn't manufactured a windplant since 1956...but people who know still fight to find one of his old second or third hand units. Why? Well, Admiral Byrd set up one of the Jacobs systems at the South Pole in 1933. On June 17, 1955, Richard E. Byrd, Jr., wrote a letter to Mr. Jacobs in which he said:


I thought it might interest you to know that the wind generator installed (by my father)...at the original Little America, was still intact this year after almost a quarter of a century...The blades were still turning in the breeze (and) show little signs of weathering. Much of the paint is intact.


Marcellus Jacobs, in short, designed good windplants. He built 'em good too...and he built 'em to last.


Mr. Jacobs now lives and works on other environmentally oriented projects in Florida and Steve Weichelt recently visited him there. During the course of their conversation, Steve asked Jacobs to describe the development of his plants and to comment on the future he sees for wind power.


PLOWBOY: Mr. Jacobs, when and where were you born?


JACOBS: I was born in 1903 in Cando, North Dakota...up near the Canadian border. Then dad moved to a ranch in Montana south of Wolf Point...thirty miles from the Fort Peck Dam on the Missouri River. Wheat and cattle country.


PLOWBOY: Where did you go to school?


JACOBS: Everywhere. I didn't graduate from any university but I went to school in several different places. After I left high school I took one year of electrical training in Indiana and a special six-month course in electricity in Kansas City. Most of my education, though, just came from studying on my own. I got the books and picked up what I could from them, and thought the rest out for myself.


PLOWBOY: Which came first? Did your interest in electricity lead you to find that you could produce this form of power from the wind...or did you set out to do something useful with moving air masses, and end up harnessing them to electrical generators?


JACOBS: It was a little bit of both. When I was still in high school I built and sold little peanut radios that operated on storage batteries...and pretty soon we wanted motors and welders and drill presses and what have you that operated on current. At the same time, I had always been intrigued by the wind. It was natural, I suppose, to put the two interests together.


PLOWBOY: I take it then that you used the wind to produce the first electrical power you generated?


JACOBS: Oh no. Our ranch was 40 miles from town and in them days, of course, there wasn't any Rural Electrification Administration lines running all over the country. Weâ€"there were eight children in our familyâ€"had to make do with kerosene lamps and so on...but we soon got tired of that. So we rigged up an old secondhand engine to run a little DC generator. But it fluctuated every time the load changed so we hooked the generator up to some old car batteries to balance the system some and that worked pretty well. Along about then, though, we started a hand forge and put a motor on that and we needed more current than our engine-driven generator would produce. This was about 1922.


PLOWBOY: And that's when you began experimenting with windplants.


JACOBS: Yes. I first tried to use a fan off one of the regular water-pumping windmills we had there on the ranch. I took a Ford Model T rear axle and cut the side shaft off where one of the wheels was supposed to go and I put the big fan on instead. Then I mounted the tail vane out where the other wheel should be...and I extended the drive shaft down to the ground where I had my generator. I just locked the differential with a pin so that as the wind turned the fan it would drive the shaft.


PLOWBOY: Did it work?


JACOBS: Oh yes, after a fashion. But there were several things wrong with the setup. It wasn't efficient, you know...there was no real gain. One of those big water-pumping windmill wheels is designed to catch all the wind in its diameter right at the start. Otherwise it'll never go. It'll just sit there. Unless the pump has lost its prime, that wheel has to lift water right from the instant it begins turning. It needs a lot of starting torque...and that's why it has so many large blades.


Once the wheel gets up some speed, however, about 80% of those blades get in each other's way. They begin fighting each other. In fact, a water-pumping windmill needs all the power it generates just to run itself in an 18 or 20 mph wind. You can pull the pump rod loose and the wheel won't run away. It can't. The force of the wind during a storm may blow the wheel into the tower and push the tower over...but the fan won't over-rev and tear itself apart.


The wheel we finally came up with for a windplant, now, is altogether different. There's no load on it at the beginning, you see...just the very slight drag of two ball bearings. The three little blades sticking out of the wheel's hub are all you need to start the thing turning in a two mph breeze. And those narrow blades are also all you need to catch every bit of air that moves through the wheel's diameter when the wind blows 20 mph. They'll do it better than all those sails on a water-pumping windmill's fan too. A three-bladed windplant propeller may develop between six and eight horsepower in an 18 mph wind, while an ordinary windmill wheel of the same diameter sitting right beside it won't produce much over two.


PLOWBOY: How long did you experiment with the old water-pumping windmill fans before you gave up on them?


JACOBS: Well, we messed around for three years or so. We even made a governor that turned every one of the bladesâ€"to feather themâ€"on such a wheel...but there were just too many other factors working against the design. To put it very simply: If you can catch all the wind that moves through a certain diameter with three blades, there's no need to have fifty of them hanging out there. The extras just get in the way.


PLOWBOY: But why three? Why not two blades? Or four?


JACOBS: We tried them. We tried those other numbers. See, I learned to fly in 1926 or '27 and that gave me the idea that an airplane-type propeller was what we wanted. Most of those props, of course, had only two blades so that's what we used.


PLOWBOY: You took one right off an airplane?


JACOBS: No. They didn't have the right pitch. But we made some windplant propellers that were quite similar to the ones used on aircraft. We didn't stay with them long, though. I discoveredâ€"very early in the gameâ€"that a two-bladed propeller has vibration problems that a prop with three blades doesn't have.


PLOWBOY: But we're still using two-bladers on airplanes!


JACOBS: Not always. When Curtiss-Wright developed some of that company's first really big engines at the start of World War Two, they found that the powerplants tore themselves right out of their mounts when the planes were kicked into an abrupt turn. I won't go into a long, confusing explanation of why this happens. It's enough to say that the Curtiss-Wright engineers and test pilots wrecked a bunch of aircraft before they finally solved the problem by going to three-bladed propellers...something I had done years earlier with my windplants.


See, this potentially destructive situation always exists with propellers that have two blades. It's always there but most of the time it doesn't give airplanes any trouble. I mean...when you make a turn with a plane, how large a curve do you usually fly? A quarter mile? Half mile? That's not nearly sharp enough to cause a problem. But a windplant supported in its center on a bearing whips right around, doesn't it? There just isn't any way to make a two-bladed wheel hold up on a windplant. Sooner or laterâ€"and probably soonerâ€"it'll snap off at the hub...or one of the blades will let go.


PLOWBOY: But a three-blader won't.


JACOBS: No.


PLOWBOY: OK. Why wouldn't four blades be better yet?


JACOBS: Well, there'd be no object in going to four.


Look. It doesn't matter if you have one blade or a dozen...if you design them right you can make that wheel catch all the wind that comes through it. You can stand behind those spinning blades and strike a match and it'll hardly blow out. You're catching all the wind, you see, and slowing it down and changing its direction. One blade is just as good as four or five or more.


The only trouble with one blade, however, is that you can't balance it...and two blades have the vibration problem I've mentioned. A wheel with three blades nicely solves both these problems and you'd be foolish to add any more.


PLOWBOY: Why?


JACOBS: Because the tips of that wheel are moving through the air at 125 mph and every time you put on another tip you're adding unnecessary drag. It takes a lot of energy to push something through the air at 125 mph, you know. That's a waste of power.


There's another factor involved too. We wanted our windplantsâ€"which had 15-foot-diameter propellersâ€"to develop their maximum charging rates in a wind of, say, 20 mph...but we didn't want their tip speeds to exceed 125 mph. A three-bladed prop met these requirements admirably.


PLOWBOY: All right. This takes us up to about 1927. What happened next?


JACOBS: Well, once we had the propeller design worked out, we still had two main problems: speed and pressure. If you want to get as much power as you can from a light breeze, you've got to have a propeller of large diameter. But when you have a large diameter, you've also got something you can't control in a high wind. You need some way to regulate your propeller's speed and you want to be able to take the pressure of the wind off your blades during a real gale.


So I developed the fly-ball governor. I mounted weights on the hubs of our propellers so the centrifugal force of higher speeds would twist all three blades identically, see, and change their pitch. This automatically feathered the propellers in high winds. It both slowed them down and relieved the pressure against them.


PLOWBOY: There's another kind of governor, you know...made by the Zenith Corporation.


JACOBS: They call that a governor! It's like holding the throttle down on your car while you step on the brakes to slow down! Their blade is fixed, you see, and when you apply a brake out here the way they do, you only slow down the propeller. You don't relieve the pressure of the wind blowing against those blades. I've replaced hundreds of those windplants when storms just pushed their blades right into the towers.


PLOWBOY: Your plants never had that trouble?


JACOBS: Never. We set the centrifugal controls so our blades couldn't receive more than the pressure for which they were rated. We've had winds of more than a hundred miles an hour on our plants down there at the South Pole. No problem. We've had plants scattered all over the West Indies and on the Florida Keys, and we've never had one go down in a hurricane yet.


PLOWBOY: Did you patent your governor...


JACOBS: Yes, but Curtiss-Wright stole it from me on a technicality.


PLOWBOY: ...and did you start putting it on windplants?


JACOBS: Oh yes. We built about 20 or 25 plants out there in Montana from 1927 to 1931. They all had our new propellers and governors on them and we sold them to ranchers in the area.


PLOWBOY: What did you use for generators?


JACOBS: We bought our generators from Robbins and Myers and we built both 32- and 110-volt DC systems. I think we got our towers from the Challenge Windmill Company in Batavia, Illinois. The towers, you know, were actually meant for water-pumping windmills. Nobody else was making windplants. We invented the business in North America...I guess the world. A few others were playing around with ideas but we were the first to manufacture a practical machine.


In 1931 we sold our ranch holdingsâ€"my brother was with me at the timeâ€"and I formed a Montana corporation, sold stock and really set up to make windplants. Later, of course, I moved the operation to Minneapolis.


PLOWBOY: Did you go right into production on an assembly line basis back there in 1931?


JACOBS: No, we spent about a year or better designing and building a big generator. There wasn't one available at that time that would produce 2,000 watts of power at our working range of 225 rpm. You couldn't buy one anywhere, so we designed and built one just for our propeller.


Now this was quite important for a couple of reasons: Number one, there's a lot more to good propeller design than most people realize and, number two, the best propeller in the world isn't worth much if the generator it turns isn't exactly matched to the prop.


See, the whole idea of high-speed propeller design is to throw the wind that hits the blades...the whole idea is to throw it out quickly. You don't want it to drag all the way along the back of the blades. That's a tremendous amount of frictionâ€"a tremendous forceâ€"and you want to eliminate it. Sometimes a very little changeâ€"a 64th of an inchâ€"in the curve on the back of a propeller can affect its power output a seemingly immeasurable amount.


Well forty years ago, I designed a special machine that would let me determine just how efficient a blade design might be. I had a test stand made up that extended out two feet past the end of a propeller and at each foot along the arm we mounted a separate wind pressure gauge. We checked a lot of blades on that stand until we knew exactly how to design a propeller that was as efficient as we could make it.


PLOWBOY: And then you built a generator to match the prop?


JACOBS: Yes. We had to balance the generator's load to match the efficiency of the propeller. If your blades work best at a certain rpm in a 7-1/2 mph breeze, they should turn exactly twice as fast when the wind blows 15 mph, shouldn't they? They won't catch all of that 15 mph wind unless they do, will they?


OK. The trick is to design the generator so that its load increases just fast enough to allow the propeller to double its rpm as the force of the wind doubles. And that's what we did...right up to the top speed we wanted, which was 18â€"20 mph.


Now this wasn't easy, because a conventional generator doubles its output when its speed increases by only something like 25%. Obviously that wasn't a very good match for our propeller...so we tried several things until we finally came up with a special alloy for the field poles in the generator. We finally got a combination that made the load of the generator fit the output power curve of the propeller over the entire range of windspeeds up to 22, -3 or -4 miles an hour...where the blades were set to feather out.


It was a lot of trouble, but it was worth it. Wincharger, for instance, didn't take the time to balance the components of its plant in this manner and that unit was only one-third as efficient as ours at higher windspeeds.


PLOWBOY: Wow. You really took pains to design and build the best possible windplant, didn't you?


JACOBS: Oh yes. I've only told you a part of it. We came up with our own special brushes in the generator, you know.


It's not too hard to set up a big DC generator and run it with a stationary engine, see, because you've got a fixed speed of operation and you can adjust everything so it's working the best for that rate of output. Now I'm particularly thinking of the commutator arm and its brushes which slide from one wound coil to another inside the generator. Every time those brushes move from coil to coil, you know, they want to throw a spark. When you break DC you get an arc...and those flashes will burn little rust spots on the commutator and then it'll just grind the brushes off in a matter of months.


What you look for, of course, is the neutral zone...the one small area where your brushes will throw the least spark as they leave one coil and go to the next. This isn't too hard to find and when you've got a fixed speed on your engine and generator you can set everything just right to make use of it.


A windplant isn't like that, though. It's set to kick its generator into operation at about 125 rpm and it reaches full outputâ€"3,000 watts or whateverâ€"up around 225 rpm. Now that's OK...but every time the rpm variesâ€"and it can change a thousand times a dayâ€"the neutral zone shifts. No matter how you adjust your commutator, then, your windplant's brushes are going to be set to throw a much bigger spark than you'd like as they move from coil to coil during the greater part of the plant's operation.


Everyone in the business faced this problem, of course, but none of the others ever licked it. We did. I developed a brush made up of a layer of graphite, then carbon, then graphite, then carbon. This gave us a brush with a high cross-section resistance. The DC current would practically quit flowing before the brush made its jump from one coil to the next and that was just what we wanted.


We tried to get National Carbon to make these, special brushes for us but they weren't even interested enough to send a man out to see us. Stackpole couldn't understand what we wanted either but they did build the brushes to our specifications and that licked the commutation problem. We've had plants run ten or fifteen years on their original set of brushes. That's unusual. Ask anyone who's operated other manufacturers' windplants.


PLOWBOY: Didn't you also make some noteworthy breakthroughs in the way you regulated the voltage of your units?


JACOBS: Yes. That's another tough situation you have to face with DC. To change the irregular power generated by the wind into a steady flow of current for use, you have to go through batteries. The only trouble is that you can't let your generator feed the same amount of electrical energy to the batteries all the time or you'll burn the storage cells out. As a charge is built in a battery-as the battery becomes more nearly "full"â€"you want to charge it at a slower and slower rate.


Well, Wincharger and all the others tried this and that but they never came up with the voltage regulators and cutoffs they needed to solve the problem. That's why you always had to get up at two o'clock in the morning or some other unhandy hour and shut those plants off to keep them from burning out their storage banks.


We had the only windplant that didn't have this trouble because ours was the only one which was completely voltage regulated. Our controlâ€"we called it the Master Mindâ€"inserted a resistance into the generator fields to weaken their output as the batteries filled up.


Now that was a problem in itself because the Master Mind contained a set of points that had to open and close thousands of times a week. This meant thousands of arcs and flashes. Eventually the points would stick and make the generator begin to run like a motor as soon as the wind died down. That wasn't good, you know, because it would soon drain all the energy stored in the batteries.


We licked that one by developing what we called our "reverse current relay". We ran a little bit of direct currentâ€"opposite in polarity to the main flowâ€"right back through the points to make them open with one quick flash instead of just hang there, floating, until they'd burned themselves out. It was a little shunt circuit, actually, that opened and closed the main cutoff with one clean action just when we wanted it to.


PLOWBOY: How long did it take you to figure all this out?


JACOBS: Well, from the time we started fooling with windplants...about ten years. Our most important work was done in less than two years...from 1931 to 1933. By '33 or '34 we were in pretty good swing. We came up with a few improvements as we went along, of course...but after 1936 or '37 we ran for 20 years without making any basic changes in our design.


PLOWBOY: I suppose you brought in an expert from time to time for consultation.


JACOBS: No, because back then there weren't any experts on slow-speed electrical generation. There were no experts on voltage regulation and nobody had ever heard of making an airplane-type propeller for a generator. There were no books on the subject...nothing to go by. I developed my own expertise. When you have a problem, you know, you just stick with it until you find a solution. That's how I wound up with more than 25 patents. Every one of those patents represents a problem that we solved.


PLOWBOY: Well it seems that there's more than just problem solving involved here. People who know say that yours are still absolutely the finest windplants ever manufactured by anybody anywhere in the world. You must have had strong feelings about the quality of any equipment that bore your name.


JACOBS: Oh sure. I'm kind of a freak, see. I want things to work forever. I built my plants to last a lifetime.


I've had battles with manufacturers all my life. When I started looking for bearings to put in our windplants, I found out that what the companies that made them called "permanent"...would last about two years. The bearings themselves were pretty good, see, but the seals around the races would dry out and let the grease inside get away after a few years. What I did was take some of the bearings used in the rear axle of a car, mount them in a special compartment with a special lubricant and then put my own seal over them. They'll last 20 years that way...and 20 years is closer to a lifetime than two.


We've had plants that have run 25 years with no lubrication. I talked to a rancher out in New Mexico last July and he's been using his for over 25. He's still using it and he's never done much more than climb up once a year and tighten a few bolts and whatnot.


The brushes on most windplants, as you know, go out all the time. They don't last long at all. Well I got a letter about a year ago from a mission in Africa. The people there bought their plant in 1936 and that letter was their first order for replacement brushes. They've used the generator all that time. Same thing with our blades.


PLOWBOY: Yes! I wanted to get to that. Tell me about the construction of your propellers. Did you make them of metal?


JACOBS: On no. Solid metalâ€"even aluminumâ€"would have been too heavy. Too much centrifugal force. The more flywheel effect you get, see, the more trouble you have shifting the plant around and that means more strain on all the component parts.


We did stamp out some hollow aluminum blades once, but they weren't at all satisfactory in the north country. They had a tendency to sweat. Frost would form on their insides and throw them out of balance...and that could shake a plant completely apart.


No. Our old standby was aircraft-quality, vertical grain spruce. Sitka spruce from the West Coast. I used to go out and select the lumber personally and have carloads of it shipped back to the factory. During the war, I had a little trouble getting the quality I wanted.


PLOWBOY: And how did you turn the raw lumber into blades?


JACOBS: We rough-cut the airfoils firstâ€"from 2 X 8 planksâ€"on a special machine. Then we put them aside in the kiln-dry rooms for several weeks to make sure they were completely set and weren't going to warp. After that we made our final cuts.


PLOWBOY: Did you hand-sand them?


JACOBS: No, we had a great big sanding machine that worked down both sides of a blade. It was set up like a planer or a duplicating lathe, you know. You clamped your raw blade into mounts on one side and then you ran a set of feeler rollers over a perfectly finished blade that was always mounted on the other side. This guided the application of power sanders to the unfinished airfoil...and you could smooth it right down to the exact contours of the master very quickly, easily and automatically this way.


PLOWBOY: How did you finish the blades?


JACOBS: With an asphalt-base, aluminum paint.


PLOWBOY: And that's all?


JACOBS: That's all they needed. Propellers we built 25 or more years ago are still going strong.


PLOWBOY: I notice that you never put a brake on your plants.


JACOBS: No, our tail vane was enough. We had it hinged so we could lock it straight behind the generator or swung away off to the side. It would remain streamlined to the wind either way, of course, so when it was in the second position it pulled the generator and propeller right around edgeways to the moving air. This took most of the wind off the blades and they'd sit up there and just idle during violent storms.


PLOWBOY: But other manufacturers could swing the tail vanes on their machines to the side too.


JACOBS: Yes, but most of them did it the wrong way. They fastened the vane straight behind the generator with springs and you had to use a line from the ground to pull it around to the side. If that line broke during a gale, there was nothing you could do about it. The windplant would run away and tear itself all to pieces...unless you had a brake that you could apply...and brakes, for some other reasons, weren't a good idea either.


We set our spring up the other way, see. It always wanted to hold the vane to the side and you had to use a line to pull the tail straight back. This way, if the line broke, the vane would pull the propeller around and make it idle. Ours was designed to protect itself if anything went wrong.


PLOWBOY: So you never used a brake?


JACOBS: We tested some when we were still experimenting out in Montana, and very quickly found that they're a source of trouble. The brake bands freeze up and you have to climb the tower with a hammer and knock them loose. Besides that, it's not very smart to completely stop a windplant propeller. The ice mostly freezes on the lowest blade and that'll wreck your plant if you turn it loose. It's much better to let the propeller swing around a little bit during a winter storm. What ice or frost it collects will be distributed evenly that way and won't give you any trouble.


PLOWBOY: Fantastic. You really checked out all the angles, didn't you? What did this translate to in business?


JACOBS: Oh, I don't know exactly. We must have built about 50 million dollars worth of plants in 25 years.


PLOWBOY: Wow! What was your biggest year?


JACOBS: I can't remember...but I think we had 260 employees at one time. We could produce eight to ten plants a day working one shift and during the war we ran three. We ran around the clock in Minneapolis and I even bought another factory in Iowa and ran it for a few years. We didn't build windplants out there but we manufactured similar equipment...electrical and magnetic hardware for the Army and Navy. Gear that protected our ships from the Germans' magnetic mines...stuff like that.


PLOWBOY: I've heard you once came up with another protective device. Something to do with pipelines.


JACOBS: Yes, I'm quite proudâ€"I'd say justifiably soâ€"of the cathodic protection system I devised in 1933. I don't know if you're familiar with the problem or not, but when you put big pieces of metal in the groundâ€"things like pipelinesâ€"they just waste away. They don't rust...but the metal is carried into the dirt by electrolysis. It's just eaten up and carried away. The earth, in effect, is electroplated at the expense of the pipeline.


I found that this action can be stopped by putting a little negative direct currentâ€"only 3/10 of a voltâ€"on the metal and a little positive DC into the surrounding soil. This discovery has saved the pipeline companies millions upon millions of dollars. All the big bridges are now protected this way too. Every very large steel structure.


PLOWBOY: Have you developed anything else that the ordinary individual would find more directly related to your windplants?


JACOBS: Well we used to sell everything you'd need on the ranchâ€"fans, motors, electric irons, toasters, percolators, freezers, refrigerators, whateverâ€"all built to run on 32-volt DC. Hamilton Beach manufactured them for me to my specifications. I even had a freezer that was so well insulated you could unplug it and it would keep ice cream frozen for four or five days. All this equipment could be powered by our windplants, of course.


PLOWBOY: Do you think those days will ever come back? What future do you see for windplants?


JACOBS: There'll always be a small, scattered market for individual plantsâ€"especially in the more remote areas of the worldâ€"but the Rural Electrification Administration has pretty well killed the demand for self-contained DC systems in this country. AC is just too readily available everywhere. Alternating current is all over the place...often at artificially low prices. That's a tough combination to beat and I quit trying to fight it in the 50's. I could see the handwriting on the wall back around '52, '53, '54...and we closed the factory in 1956.


PLOWBOY: But conditions are changing. There is an energy crisis now, you know. That AC is going to get more and more expensive and we're going to have to tap some power sourcesâ€"such as the wind-that we haven't really thought a lot about in the past.


JACOBS: Yes, but I still feel that the individual DC plant is largely a thing of the past. If I were building windplants today, I'd go AC. And I wouldn't concentrate on the small units...I'd think about larger ones that could feed directly into the distribution grid that's already set up.


As a matter of fact, I proposed just that idea to Congress back in 1952. The power companies, you know, already have a great number of steel towers set up to carry their transmission lines across the country. I added to this the fact that AC generators require almost no maintenance at all...and I came up with an idea: Put windplants right on top of the towers.


Pick a stretchâ€"I took Minneapolis to Great Falls for an exampleâ€"and install a thousand AC windplants on the towers in between. It doesn't matter what the wind does, at least some of the generators will be producing all the time. Just let 'em feed supplemental power into the grid whenever the wind blows.


The beautiful part of this plan is the fact that the wind blows strongest and most steadily when we need it most...in the winter. I've talked to the men who manage the power grid and they tell me electric heat has become so popular that they're now forced to keep thousands of dollars' worth of standby diesels on hand...just to handle the winter overload.


PLOWBOY: OK. But let's say that someone who reads this doesn't agree with you. Let's say he wants to go into business right now manufacturing essentially the same windplant you produced for 25 years. What happened to your old dies, the old tools? What about your patents?


JACOBS: The equipment is all gone. I stopped in at the factory a while back and it's used for something else now. None of the original setup is there at all. As for the patents...quite a few are public property now.


PLOWBOY: All right. Let's get even more basic. What if an individual wants to go out and build his own windplant the way you put your first ones together...with materials he finds in junkyards and other odds and ends?


JACOBS: Well I haven't been active in the field for 15 or 18 years now. There's a lot of new stuff I'm not familiar with...but I'd say that some of the AC generators and the rectifiers now available should make that pretty easy.


PLOWBOY: You're not actively engaged in windplant work of any kind at this time?


JACOBS: No, I have other interests now.


PLOWBOY; You mean you don't think about wind-driven generators at all?


JACOBS: Well...I did buy one of my old plants out in New Mexico this summer...and I've still got quite an assortment of DC equipment and appliances packed away. I'm doing it mostly for my son, you know...but I imagine I'm going to have a little fun setting that windplant up and running it this winter.

« Last Edit: April 17, 2009, 06:27:52 PM by hiker »
WILD in ALASKA

TomW

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Re: brushless?
« Reply #8 on: April 17, 2009, 06:50:10 PM »
Hopefully you cut and pasted this yard of text with permission of the author!


A link would have worked.


Tom

« Last Edit: April 17, 2009, 06:50:10 PM by TomW »

Flux

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Re: brushless?
« Reply #9 on: April 18, 2009, 04:26:54 AM »
I have been away for a week and can't be bothered to go through all this again now, but somewhere I have done a diary entry about "matching the load" and I started from the wound field perspective and then went on to the issues you meet when you replace the wound field with permanent magnets.


Yes indeed the wound field machine lets you have complete control over the load matching. What you can never avoid is the field requirements and to some extent the iron losses associated with this type of alternator. In low winds the field takes all of your power so fine for high wind operation if you are prepared to sacrifice the low wind output.


Power densities and efficiencies are higher for permanent magnet alternators at these lower speeds and the large wind power people are now going that way rather than wound field. But nothing is the perfect solution, all are compromises, and the wound field option is not entirely without merit.


The issue about voltage and also the issues of AVRs are a red herring as you will find out when you understand the full requirements for wind machines. You can get any voltage with any type of alternator. Wind power is not suited to direct power production with no energy store so an AVR is no real use and even if you try to use the internal regulator in a car alternator it will cause you many problems.


Flux

« Last Edit: April 18, 2009, 04:26:54 AM by Flux »