6/18/06 Hello, my name is Paul E. Schoen, and I have been a fairly regular contributor to the SmallEfficientVehicles group since April. That is where I learned about this group. I have become discouraged with SEV after several of my posts were disapproved, only because the moderator thought an item had been already decided, or it contained some "inconvenient truths" that he did not agree with. There seems to be a growing realization that their $5000 target will be impossible to meet, especially with the specifications and technology they have decided on. I always try to express what I consider true, and I will offer constructive criticism if I see errors in anything. It is counterproductive to argue about anything if it is not based on solid principles of physics and design engineering. However, it is certainly OK to express far-fetched ideas as a way of stimulating thought in new directions. My main experience is in electronics design, particularly high power equipment such as circuit breaker test sets, which involve the generation, control, and measurement of very high currents (up to 100,000 amperes). I am particularly interested in three phase induction motors and VF controllers. I feel that this type of motor will be the best choice for automotive traction use, and I am looking into the possibility of winding a motor for low voltage and using V/F to boost its horsepower to several times its rating at 60 Hz. I believe a motor can be made that will provide about 20 HP in the same frame as a 3 to 5 HP motor. I have wound a 12 pole motor for 8 VAC, and operated it at 180 Hz, 1800 RPM, 24 VAC. I am now working on a special controller to drive such motors directly from battery power of 48-72 VDC. It appears that the main topics in this group are on the fuel powered engine, and I agree that much can be done to boost fuel economy with advanced technology. However, I think there are advantages to hybrid vehicles, especially plug-in types, because of the lower overall energy cost of grid-supplied (or privately generated) electricity, and also the capacity for regeneration. I drive a 1998 Saturn, which has averaged 36 MPG and peaked at 46 MPG, so I know good fuel economy can be attained without severe limitations on performance. One of the biggest issues is the competitive and aggressive mindset of many drivers, and the HP wars which cater to that. Once people view driving as a cooperative venture for the purpose of transportation, rather than a thrill ride or compensation for inadequacy, they will demand more economical vehicles, and the roads will be a safer place. I hope I can be of some help in this worthwhile project. Paul ================================================================================================= 6/23/06 I see that there is not much activity in this group, and most of it lately concerns the fuel-powered motor. There were also some valid suggestions to direct efforts toward building some sort of actual vehicle, which would be a way to validate some of the proposals and discussions of alternate ideas. As previously stated, my main interest is in AC induction motors, and using PWM techniques to extract maximum HP from the smallest possible size, at lowest cost. I think the most successful vehicle will be one which uses electric motors for traction power, and an advanced high efficiency fuel burning engine for long range capability. I am fascinated by the possibilities of the Tesla engine, and it seems a good candidate for this purpose. A very practical project may be the addition of an auxiliary electric motor drive package to existing FWD vehicles. This essentially creates a hybrid with two propulsion systems that can be used independently or together, for redundancy, and optimal performance and economy in various conditions. It is possible that this configuration may also produce the most practical ground-up design. As I understand it, the overall drive train computer will control all aspects of the vehicle's operation, and in the case of a hybrid, it could choose which propulsion means is most effective in any situation. However, there should probably be separate embedded processors in each subsystem, and a way to decouple the main computer so that either subsystem could be used in case of a problem. I hope to be able to stimulate more lively discussion in this group. That is what I enjoyed in SEV, until it became a frustrating argument of common sense and basic physics against an unreasonable dream. ================================================================================================= 6/24/06 That might be a good design for a maximum efficiency personal vehicle, but I doubt it could ever be commercially viable to a reasonably wide market. I think a three wheeler in this configuration may be more stable for emergency braking and cornering, but a four wheel design is probably more practical for a two passenger or four passenger vehicle which will meet the needs and acceptance of most people. I sense that a major emphasis in this group is new or improved ICE technologies, and the development of the advanced motor controller. However, there needs to be a specific goal to shoot for. Once an acceptable prototype concept has been specified (at least overall parameters), specific parts of the vehicle can be worked out and the best overall design can be achieved. Being new to the group, I may have missed some of this, but perhaps some sort of cooperative Wiki can be set up to allow members to contribute portions of the design in their respective areas of knowledge. Once such a concept has been formed, and a consensus reached on some details, maybe we can start assembling an actual prototype. Of course, this would need to be done at a particular physical location which may not be accessible to most members. If anyone has access to a school with a good automotive and metalworking shop, that would probably be ideal. Possibly several different prototypes could be assembled in different locations. I am just anxious to get something going beyond discussion and get some hands on experience. I may still develop my hybrid accessory and attach it to my spare vehicle (a 1997 Saturn SW1), which was officially totaled but is still driveable. My main problem now is making an inexpensive transmission to obtain sufficient starting and hill climbing torque, as well as a reasonable top speed, with small electric motors. Paul ================================================================================================= 6.24.06 I agree that series wound DC motors have good low end and stall torque, but they suffer from high maintenance and limited regen capability. They were used in older locomotives, but newer ones use ACIMs, if the following link is to be believed. http://www.railway-technical.com/tract-02.html There must always be a controller between the battery bank (and/or supercapacitor bank), so that the motor can be supplied with only just what it needs for propulsion, and convert its regen voltage into the proper values for charging the capacitors and batteries. The main problem with an ACIM compared to a series (or shunt) wound DC motor is that it would need a mechanical transmission for optimal efficiency without resorting to an oversized motor. I have some ideas for such a transmission, which would be essentially a planetary drive with electrically driven (tooth) clutches to change ratios, and would do so only when the motor speed is synchronized to the selected ratio. Precise speed control such as this is easy to do with an ACIM. It would be nearly impossible with a commutated DC motor. A BLDC would be a good choice, but they are expensive and not as rugged, and require accurate speed and position sensors. A very real problem with bolting a motor to the wheel hub is that it greatly increases the inertia of the wheel so that it cannot respond as quickly to bumps, and produces a rougher ride, as well as putting extra strain on the tires. Paul ================================================================================================== 6/25/05 I was under the assumption that the curves were for a VF drive. Otherwise, the torque would be between the stall torque or breakdown torque at anything less than rated speed (synchronous speed - slip). These torque values are something like 2x to 3x rated torque, depending on motor design. I don't think you can get any more torque by using a VF drive, but you can definitely operate more efficiently at variable speeds. Efficiency probably drops considerably when operating any motor beyond its rated torque, as it is generally proportional to current. A motor with 90% efficiency probably loses 5% due to copper losses. Pushed to 3x, copper losses of 9 times that amount are possible, so efficiency drops to about 50%. This is probably true also for motors with higher peak torque, such as BLDC and series wound DC. This may be acceptable for short duration surges, but then sufficient time for cooling must be allowed at less than rated torque. I was impressed with the specifications of some of the BLDC motors for vehicular applications. They are believable if you take into account the fluid cooling requirement. However, costs of this type of technology are quite high compared to ACIMs. Please check out the links I added under a new folder for traction motors. Some of the concepts are quite interesting, especially the Ironless Wheel Motor. I have not found much research on higher frequency ACIMs, as I have been investigating. The only limitation to this seems to be more iron losses as frequency increases, and I saw a reference where this becomes most significant above about 180 Hz. However, there are 400 Hz motors which appear to be in line with my estimation of at least a 3x to 5x reduction in size and weight for ACIMs. Thus it may be possible to make a 15 HP motor that is only about 150 lb and perhaps 8" dia and 12" long. Paul 6/26/06 Iron losses, as I understand it, are caused by heat generated in the iron rotor and stator due to magnetization. It is essentially a mechanical process of realigning molecules, which creates friction. Higher frequency does this more often, creating more heat. Better magnetic materials and thinner laminations reduces this effect. An ACIM has typically low losses in the rotor, because it can be constructed with very heavy windings running at high current and low voltage which needs very little, if any, insulation. I think I saw a chart indicating about 20-30% of total losses in the rotor. This is good, because it is difficult to extract heat from a rotor. A BLDC uses magnets in the rotor, but there is still iron to complete the magnetic path. The stator current is used exclusively to attract the magnets in the rotor, rather than inducing current in the rotor, so I would guess this gives this type of PM design a 50% edge on ACIM. So, efficiencies about twice that of an ACIM are to be expected. This is in line with the published figures. In both cases, most heat is generated in the stator, and it is generally caused by copper losses, which increase with temperature. Thus, fluid cooling can greatly increase efficiency and allow for greater overloading. In an ACIM, as for transformers, higher frequencies allow more power in smaller volume and weight, but in ordinary motors the iron losses become significant at (so I am told) about 2x to 3x, but 400 Hz motors are available, so it can be at least 6x with proper design. The additional expense of better materials and thinner laminations should be offset by the smaller size and weight. This concept could be proven by building a motor, but there are many factors involved in making one that has optimal characteristics. Some factors, such as rotor skew, and ratio of stator to rotor slots, seem to be almost a black art. There are some motor design software packages available, but they are very expensive and seem (to me) difficult to use. I would leave that task to an experienced professional. It would be very expensive to build a number of experimental motors and test each one. It does not cost much to rewind existing motors, as I have done, but those designs were not optimized for the number of poles and higher frequency. I think this would be a wonderful project for an EE program at a university, with access to the specialized tools required, and perhaps funding for this type of research. However, it seems that most efforts are going into BLDC and SR designs, despite higher cost and other negative factors. Paul I thought about using ferrite, but it is extremely brittle and difficult to form and machine. Also, high frequencies require either very high RPMs or a very high number of poles. A 12 pole motor is very common, and can be wound on a standard 36 slot stator for 600 RPM at 60 Hz, and 3600 RPM at 360 Hz. It could probably be extended safely to 4000 to 5000 RPM. For the winner in miniaturization, look for Molecular Motor. Also check this miniature high speed motor: http://www.sandia.gov/mstc/technologies/micromachines/movies/motors.html Or this one: http://www.berkeley.edu/news/media/releases/2003/07/23_motor.shtml 6/29/06 I looked through the Wiki, at least somewhat, and it does give me a better understanding of the core direction of the group. As far as I can tell, most of the effort is toward construction and testing of a PCM using an existing microcontroller specially made for the purpose. However I am not really sure about other areasof the design, such as the actual engine, driveline components, chassis, and overall concept. I am more oriented toward EVs or hybrids, although a very efficient CV, especially with alternative fuel, may be most cost effective. This is mostly due to energy storage and refueling limitations of present battery technology. My latest addition to the links, the study on EV production, seems to validate that, but rising fuel prices and battery improvements may shift the balance toward the EV. My proposal for an immediate design concept is a vehicle with conventional FWD, using an ICE for primary motive power, and a secondary RWD plug-in electric system. Each system may be configured for barely adequate (and most efficient) power, but used together, would have good acceleration and economy. In this way, the two systems could be developed and tested independently, and improvements on each may be made as testing progresses. It looks like you are looking for someone to design a PC board for your prototype controller. I have a fairly advanced PCB design system, which is Mentor Graphics PADS design suite. It is one of the leading top end systems, and is used for advanced motherboards, cell phones, defense projects, and all sorts of complex and dense circuits. There is an established community of professional users who collaborate with each other to solve design problems and give advice. I can probably help design the boards for your system, but I will need specific information about the overall dimensions, connector spacing, and the design itself. The demo version of PADS is available at www.mentor.com, and it will allow users to view the design and output CAM files, but not make changes to be saved. If you want me to help with that area, please let me know whom I should contact. Paul ================================================================================================= 6/30/06 I almost bought the Eagle package some time ago, but I was disappointed in some of its capabilities. I previously used a DOS-based schematic capture program called Futurenet, which is now public domain as far as I know. It will still run in an MSDOS window under WinXP. It can be output to an HPGL plot file which can be translated to other formats for printing. I also have a rudimentary version of a converter which will translate it to PADS ASCII format. The demo version of PADS is available for free download on www.Mentor.com, and it is fully functional for small designs. For larger designs, the output commands are disabled, although changes can be made, and then saved by ASCII export using its visual basic function. So, only one person in the design team would need the full package to do DRC and create the final Gerber files for fab. Anyone else could use the demo to view the design and even contribute changes. I think decal and part editing can be done as well. It would be really nice if we could use the open source Kicad PCB package. They are constantly improving their product, and it is freely available for download. They have a Kicad Users Group: http://groups.yahoo.com/group/kicad-users/ Another interesting package is Tina, which I have for circuit simulation, but they also have a PCB design suite for less than $1000. I had some problems with an early demo, but it has some nice features, including 3-d view of finished boards. Just some thoughts. Maybe I should try the Eagle demo package again and see if they have fixed the problems I saw a few (Maybe 5) years ago. I do not feel qualified to do much design work on the main controller, but I probably could contribute to the motor drive and battery management subcomponents. I plan to build some prototypes soon, which will include a DC-DC converter, three phase PWM VF control for the motor, and a power storage management system to handle power supply and regen for the battery bank and ultracapacitor surge storage. Paul ================================================================================================= 7/1/06 I don't know if this could be done practically as a home project, but it would probably require the ability to control the valves (or a part of the camshaft) so that the unused cylinders would not perform compression or intake. Possibly the cam could be locked in the exhaust position and cut off fuel injection to the unused cylinders. It would be simple with electrically operated valves, but I don't think any standard automotive engines have them. Also, there is often a valve clearance problem that will not allow a valve to stay open for an entire revolution. There are some newer engines that use multiple displacement, and there is also an engine that has an electrically operated camshaft to vary the valve timing for maximum power or economy as desired. Probably a lot cheaper and easier to retrofit with a more efficient engine or just get a complete car designed with fuel efficiency as a primary goal. Another option is to add a small electric motor/generator to the fan belt system, and use it to charge batteries during downhill (with the main engine turned off), and then provide a little bit of power for cruising on flat terrain. I once found a website that described this idea for performance enhancement. The main engine could be restarted just from rolling inertia when needed, especially with a manual transmission. This would work even better if there could be some sort of compression release to allow the engine to turn more freely. Otherwise, perhaps use the engine as a pump to compress air and then use that with some pneumatic motors to provide extra power. BTW, check out this link I found while searching for information about this concept: http://www.mrcontrols.com/primers/ems.htm Paul