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Permanent Magnet Generators - PMGs
120/240 VAC 60HZ 3KW Utterpower PMG
Overview This page under development
Neodymium Magnets are many times stronger than the magnets we played with as kids, in fact 'Neos' of any size are down right dangerous to play with. Our interest in this material is building compact and extremely reliable generators and alternators that follow the KISS philosophy of Design. There is no doubt in my mind that the generator I describe on this page is the 'MAD MAX' choice of all generators. If you didn't see the Mad Max movie, (science fiction) it's about the future; a time when energy is scarce and expensive, and everything you own better be tough as nails, because replacements aren't going to be easy to find at any cost. I consider myself very fortunate to be in communication with people around the world who live off the grid, some are in the jungles of South America, some in harsh environments in Africa, and still others are living in climates where -20F is not considered all that cold. My friend Mamad in Iran has probably been to some of the harshest environments anyone could imagine where he made repairs to equipment he specializes in. Mamad for one knows what it takes for machines to survive in these hostile places, it's often all about simple and rugged design (KISS engineering). It just doesn't seem to matter where the generator is or how it's used, 99% of all reported failures of Generators (Alternators) occur in certain components. If the Generator has a voltage regulator, this is the device that often fails, and it is also reported as the most expensive item to replace. Fact is; some people report that buying another generator was cheaper than the estimated replacement or repair of their voltage regulator. Other items responsible for failures are rectifiers that supply the DC current to the field winding, brushes or brush holders, worn out slip rings, broken or damaged wiring associated with the brush rigging, and defects in the field winding on the rotor. In the case of the Brushless Alternator designs, there are components on the rotor that fail, Caps for one. Some Brushless Alternators have an access door that will allow you to replace these components without taking the generator apart, in other generators; you're in for some work. Unless you have the skills to replace even small parts, it's going to cost you considerable money to get a generator head repaired, and if you have to ship it off to a service center, it's usually a major expense and inconvenience. As you already guessed, the PMG doesn't have any of these components, and if there ever was a Generator designed to survive an EMP, this is it! No electronics of any kind. The fewer the number of components, the less failures. Until recently, the only PMGs I could find were Military pieces, (like those in aircraft) that were designed to be both lighter and more reliable, but these are far from the devices most of us want for making our own power. I did find a few hobbyist that were using Automotive Alternator housings and making their own rotors to produce some lower power PMGs but I find these less than suitable for my applications. A friend and AE enthusiast in the NE ordered one of the PMGs built on an Auto Alternator Frame, he promptly burnt it up running it at it's advertised KVA output while charging batteries. If you buy one of these, I suggest you monitor the temperature of the frame, and talk to the vendor about how hot you can get it before damage might be done. Of course warranty periods are a nice thing to note before you purchase. In 2005, I placed an utterpower built Listgen 6/1 in an off gird location in the North Western Cascade Mountains in Washington State. This unit usually runs six to eight hours a day, the test site is rather perfect, (no mechanical skills in the house hold) and until last month the family had no idea they were running one of the more powerful 60HZ 120VAC PMGs I've ever seen. This family will readily admit that this 60hz generator set has not received the best care, yes there were water leaks in the cooling system, but nobody thought that adding all that water would dilute the antifreeze and lead to a broken water jacket one morning. We all know about JB Weld, and the visiting Son patched the unit back up and saved Christmas! But sooner or later, the cooling water got too low, and the BIG overheat came... I've seen heads so hot, the paint turned black, and fell off in big flakes. BUT not all heads survive this, and this one didn't and finally (after time), it got bad enough where the engine wouldn't start. They installed a new head, and were quickly back in business. The family does have a 5kw gas backup, but the cost of fuel is several times greater than the cost of running the ListerPMG, so there's a panic to get it running fast when it fails. As poor as the install is, (my opinion) there's been zero problems with the PMG. Just to note, total harmonic distortion on this machine was measured at 4%, and this 3KW (conservatively rated) unit has carried 4000 watts plus for some hours without over heating in the LAB and again in the field. That's well beyond what most off grid families ever need, and there's still far more surge capability left! One of the strong points of this design is it's ability to start larger induction motors like those found in 240 Volt well pumps. In a lot of locations, if you can't start the pump, you haven't found the right solution. In my opinion, there is a reason to utilize the AC generator for charging batteries, in many cases, it's just too easy to select an Inverter with a built in battery charger and AC transfer switch, AND take advantage of the convenience. If you think you need more DC charging capabilities, it's just too easy to add a heavy duty battery charger that has AC input. The AC generator gives you the ability to carry your important AC loads when your inverter goes down, and if you selected a DC only generator head for your back up unit, you might have less options, and you might want to consider a backup inverter, and maybe a spare DC generator head. This Little 120/240 AC unit will allow you to run a 240 VAC wire feed welder, and get a critical job done. People will argue what off grid power design is better, and some will say they don't have a use for 240 VAC. It's always true right up to the point where you really need it. In 2007, the PMG has been further refined, with units in the jungles and harsh saltwater marine environments. So you ask... if they're so good, why doesn't Sears and Roebuck have them? I think part of the answer is the EXTREME effort it involves to properly engineer a PMG for a specific use, unlike the Synchronous Generator; you can't tweak the field current to make it right, you need design it exactly right, and you need to design it all over again for each model. There are certainly more challenges beyond that, you don't go to "magnets are us", and stick them to the rotor, each magnet is custom machined, then charged and >certified< to have the proper flux density; this is a time consuming process, but it is the only way you can get superior voltage droop from no load to full load, and again, we can't cheat by increasing the current in the field, because we have no windings in the field. We also need to note that the PMG rotor is currently far more expensive than a few turns of wire, and the other components used in the more common designs, but this unit will compete when we consider delivered price, and the cost of shipping a replacement unit will be a fraction of the cost of some of the current and more popular off grid generator head solutions. Other problems with the PMG design involve air flow and properly cooling the Generator while keeping dust and dirt out that erode the protective coatings off the magnets, and stator windings. The Utterpower design cools the rotor directly, but it's a sealed unit, so no dust or dirt is blown thru the stator windings or past the magnets to contaminate the inside of the unit. Open framed PMGs can prematurely fail as we soon learn that there is a lot of ferrous materials in soils and in and around the typical operating environment of a generator set. We must remember just how strong these magnets are. There are several test sites where the Lister 6/1 and PMG are the source of power feeding (AC IN) to inverters that are known to be a little particular as to the Frequency and voltage of the generators, and this PMG makes a nice clean sine wave and the appropriate peak voltage to make these Inverters and their built in charging units happy. The model 1003 120/240 60hz unit is a perfect match for the mighty 6/1, and it can make all the current that the massive flywheels can help deliver for starting heavy loads like well pumps. One of the major advantages of the PMG is it can be sent via UPS, or FEDEX. This is a major savings over other generators all by itself, and as we know, the cost of fuel continues to increase the cost of truck shipping. The voltage droop in the utterpower PMG will allow you to operate at 60hz and meet ANSI C84.1 from no load to full rated load, and if we look at the ANSI utilization chart, if your distribution system is short or heavy gauge; you can place a 48% overload on the PMG and still meet the standard in many cases.
More info to follow on Permanent Magnet Generators (PMG), we have prototype units in the field now. We are taking orders, and will start filling them in February 2008. Simply send me an email to get on our notification list. We will market thru Associates The Watt Shop in New Zealand is currently selling the 50hz version of this unit, and others are waiting for production to catch up with demand. If you're in NZ, consider Darren Hill at the Watt Shop for all your off grid power requirements. A fun experiment to show the kids. Neodymium-iron-boron (NIB), often called NEOs for short hand, are many times more powerful than ceramic, ferrite or other magnets we grew up with as kids. If you dropped a spherical shaped ceramic magnet down a piece of Aluminum pipe, it will fall thru the pipe slower than a ball bearing by a noticeable amount, depending on the field strength of the magnet, you might need a keen eye to tell the difference. Now drop a NEO down the same Piece of Aluminum pipe, and it will literally appear to hover in the tube, I think it took 5 or 6 seconds to drop all the way thru the 3 to 4 foot thick wall tube I used. NEOS are VERY strong indeed! You can buy round Neos from several vendors, otherpower.com is one source. New 186_PMG_GEN Prototype
All the best George
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