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Utterpower PMG Q&A
Q. Why do you rate the smaller PMG at only 3.0KW continuous when you say you have ran it all day with a 4.2kw load on it? Aren't you losing customers by under stating the capability of the alternator? A. One of the first deployments for the PMG was part of a mission critical multifunctional APU (auxiliary power unit) that might see 150F temperatures in the compartment it lives in. It was a concern as to how much load we could place on it and still assure it ran cool enough. In our tests, we find that running 4KW is no problem at all as long as the ambient temperature is reasonable, I think if you have the alternator out in an open space where air can flow around it, and the temperature is reasonable, then a 4kw continuous load could be reasonable. Some think they might need more generator to handle the peak current required to start an induction motor, following are two screen screen shots that show you just how good the voltage is even with 5.55 KW of load on the unit! Yes, that's right, the unit is still supplying 224 volts (112 when wired parallel) at this load.
Above: 3KW unit on Utterpower Test Bench, note the load is pure resistive (PF=1.0). Almost 50 honest Amps and still well above the voltage allowed by the ANSI standard. If I find a hydro site where fuel or cost of electricity is not a factor in conducting a two week or longer test at let's say 4.2 KW, we might raise the continuous ratings, but for now, I think the people who frequent here know that there are generators sold that will flat burn up at their advertised ratings or the voltage will be so low that they'll be afraid to run at those advertised loads. Bottom line... don't compare this head to other heads rated at only 3KW unless it's designed for the military Q. Does the PMG run and make power all by itself? A. Yes, I get this Question more that you think... Answer is No, you need some source of power like an engine, hydro wheel, wind turbine, etc.. This is not a magic device, there are no free lunches in Physics, want the promise of a free lunch? Talk to a Politician or find the many scams on the internet that discuss HHO generators and other things designed to remove money from your pocket and give you zero return on your investment. Q. How much horse power do I need to run the PMG? A. This depends on what you expect to get out of it in the way of power, a rule of thumb is two horsepower in for every corrected (honest) 1000 watts out. Be careful what you read on the internet, I have seen a number of claims where people put 3000 watts of lighting on a generator and claim they have a 'real' 3K out and far less horsepower in than 2HP per KW, always do the math and don't be fooled by those who don't know what they're doing, or attempt to deceive you in order to sell you their stuff. Q. Why a PMG? Isn't there enough Generator choices out there already? A. For those of us that want assurance we can make back up power in emergencies; there are all too few generators that can survive being run weeks or months in service without problems. If you own the Utterpower PMG, it's easy to replace the engine if necessary and keep on running, Q. What Voltage does the PMG operate at? A. North American Standards allow us to operate as high as 127/254 volts, or as low as 110/220 (at the end of the distribution point). The PMG produces 127/254 at 60hz no load, and at a severe overload of 140% the PMG is still within the Spec for voltage droop, this is all done without a failure prone voltage regulator. Of course voltage droop is far better than just meeting our Standard when we observe the continuous rating of the PMG (3000 watts continuous), but the 4000 watt plus overload never seemed to get the unit very hot in our low ambient Summer temps here in Western Washington. The very low (extremely conservative) rating assures that this unit can run in a very warm and harsh environment and still meet it's rating. Q. What about high temps and low temps, can this damage the magnets used in the PMG? A. The PMG has been ran at rather extreme temps inside a box with heat added, the temp that would cook out any properties of the magnet is significantly hotter than any temperature we will see in a machine room or in a natural environment. As per cold, this only increases the performance of the magnets AND the copper windings, it does not affect the magnets or their properties to cycle them thru bitter cold temps. Q. Are there any serviceable parts inside? A. Not really, the front bearing on the shaft end (the one that sees the load) could be 'changed out' in the field with a few minutes of training, this can be done without pulling the rotor. In countries where there is not yet a repair facility, we plan to work with DIYers to allow them to safely change the rear bearing (requires removing the fan first). We are assembling with high grade bearings, and we expect these to run for many years before a bearing change is necessary. Q. I received my unit with a pulley, where do I get a belt for it, and why don't you sell them? A. We adopted the "K" Section Automotive belt because it can easily carry the max load and it's very easy to source the belt at reasonable cost, we recommend the 8 rib belts, but many use less expensive six rib belts without any problems. remember... using readily available parts is part of KISS engineering. To use some industrial belt because you think it is better just sets you up for a sourcing problem. Q. Can I spin the alternator either direction? A. Yes! Q. Why do you use a tapered bushing pulley? What's the advantage? A. Taper Locks are popular in commercial applications, it makes it VERY easy to place a pulley and to remove it, even with gloves on in sub zero temps. There are several ways to install these pulleys, but I recommend that you place the pulley on the shaft, and then put the Bushing (taper lock) on the outside. Use the Metric bolts AND the metric threaded holes in the pulley to secure the pulley to the shaft. Tighten evenly, each bolt a little bit at a time in a circular pattern, and don't use two hands on the wrench! No need to get them REAL tight, as they lock up pretty solid 'snugged up'. The jacking holes (threaded holes) are normally used to remove the pulley. Once you learn the advantages of taper locks, you'll find it hard to use anything else. One trick in installing the taper bushing, insert a screw driver in the slot, tap it in with a hammer to spread it a little, and it will slide on the shaft easy. Q. How do I check the Stator wiring, I want to be sure it's right before I run it. A. See the charts that show open circuit voltage output at rated output, verify that your stator puts out the same voltage. Also see the PMG testing Page Q. How do I check stator wire designations? , I want to be sure they're right. A. This is a good idea, I don't expect you to find trouble with the PMGs, but I have found several ST generator heads with the wrong designations on the leads from the factory. Here's how I quickly test and wire PMGs. see PMG testing Page Use a 12 volt light bulb, an incandescent tail light bulb or similar is all you need to make the basic checks and then wire correctly. Start with all leads separated, if any are strapped together, then remove the straps. You can find the ends of the windings by putting the light bulb across them, a simple twist of the shaft, (do it fast), and the bulb will light bright. Find both Stator windings one at a time. Note, if you short the ends of one winding together, it's hard to turn the shaft! 1-////////////-2 should be the first winding. 3-////////////-4 should be the second winding After you've proven the above combinations light your 12 volt incandescent bulb connect up the following 1-////////////-23-////////////-4 (make sure 2 and 3 are strapped together With the above configuration, place your 12 volt bulb across one and four, give the shaft the same quick twist, the 12 volt light bulb should get a lot brighter! If this is not the case, swap 1 and 2 and try again. Notice that the setup above is what you'll use for 120/240 service, 2 and 3 strapped together become your neutral. You will also note that only half the load (approximately 1500 watts can be carried between neutral and either terminal 1 or 2 in this configuration, this is typical of all generators wired for 120/240 single phase operation. If you will be using your PMG for 120 volt only, arrange the windings in the following configuration 1-////////////-2 In the above configuration, the two stator windings are in parallel, and the full 3000 watts can be supported, this is necessary when you have one LARGE single 120 VAC load. Put your light bulb across these pairs and give it a twist, if you had the two windings opposing each other, the shaft should be hard to turn. If this were the case, you'd swap 3 and 4 and try again. It should now be obvious a person could lose all the designations, and quickly sort out the leads.. Q. How do I wire in a fuse box or breaker panel? A. See the ST pages, how you wire it should be the same except for breaker sizing and lead designations. Q. What about the new 6KW unit, how many of these have been sold? A. I shipped off out first Beta 6KW unit to Physicist, DIYer and Friend 'Moe' in Canada, he has flogged it repeatedly at his off grid summer residence in BC, he likes it so well, it's been permanently installed along with a beautifully restored Lister 12/2 CS on his property. Beyond that, we have an additional 9 units in the field, members of this group were hand picked for their skills, AND they are active in generating off grid power or serious backup power for Hurricanes or similar. to date, we have zero issues, zero reports of troubles. I hold one hot spare on the shelf here at Utterpower just in case. there are more 6KW units back ordered, and we expect notice of delivery any day.. Q. 7/26/10.. "Why would I want to buy your PMG when you say there's no way to service it?" I just bought five ST generators instead. I know I can work on them and so can my customers. A. We gladly share how to disassemble the PMG, the magnets are strong and you can easily hurt yourself if you don't follow a simple procedure. Other than rewinding the stator, there's no reason to disassemble the PMG, the bearing on the shaft side (the bearing seeing the radial loading) is easy to get at, the other one requires you to pull the fan first.You need only clean the outside of the PMG well, and move the PMG to the table top on clean news paper, remove the front end bell, and replace the bearing, we do this to assure we don't contaminate the inside of the generator. Part of the reason the PMG lives such a long life is we don't run an open frame where dirt and grit gets in and erodes insulation off windings. Each run where the generator heats and cools can drive this dirt and grit further into the windings and insulation. In the case of the ST, few in North America have played with more ST Generators or collected more failure data on them than Utterpower and friends of Utterpower. For those who study the design, we will note the ST have all failure points of a hardware store Generator, and one more. It's taken me the better part of 10 years to form opinions on the ST. One of the problems is the incredible variables between manufactures and Generator heads in the same shipment. Some of the problems noted were exploding plastic fans, rectifiers of poor quality, bearings that made noise and soon failed right out of the crate! Many of these things a DIYer can fix, but the most disturbing problem some of my field contacts reported was excessive slip ring wear. This is NOT a minor problem for those who will run long hours off grid, one company in Hawaii reported one of the slip rings was so bad at 2000 hours of logged running time, that they were forced to remove it from service. The stock slip rings are installed by placing them in a fixture and then injecting plastic around them, I have seen a percentage of them that don't run true, but I suspect that one of the contributors to slip ring erosion is the alloy they use. I think the Chinese have found something that works and is far cheaper than what we would specify if we were building one for ourselves. I believe there may be a market for a kit to rebuild the slip rings in the field, the 5KW rotor can weigh upwards to 70 pounds, it also needs special crating to assure the bobbins are not damaged, so sending off the rotor for repair is going to be expensive! Maybe as expensive as buying a new one? Fact is... fuel in many third world countries is so expensive that power plants are often run only long enough to grind grain or pump water up to a tank for a remote village, if these slip rings work for 99% of the common applications, maybe they did the right thing by using a cheaper slip ring material and lowing the price? Those with Hydro power make valuable reports. I have one customer (well he was a customer till I sold him two ST generators). Both units lasted less than a year each before the slip rings failed entirely. I did write an article (on my CD) that explains what you can do to minimize this problem, but as you might guess, reversing the polarity of the field current at regular intervals helps but does not cure the problem. The bottom line? The PMG is a reliable generator with none of the problems the ST has, due to shipping charges and the fact the drive system is far less expensive, the PMG can often be delivered to the customer cheaper than an ST head. This is the one you use for your personal generator build..
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