Sorry, that last email got screwed up somehow. Norm wrote;
Tesla was a sad genius. If he had just a little of Edison's interest in marketing he would have been wealthy enough to finance his all of his scientific investigations to his heart's content. Reply; Well, as I recall, according to an article in "Invention and Technology" magazine some years back, he DID have a big percentage of Westinghouse's profits by contract for his poly-phase AC generating stations at Niagara Falls, but they soon realized that their future investors would not be happy with that deal and reneged on the contract. If they had not, Telsa's ancestors today would probably be very wealthy indeed! Or maybe he would have just built even larger wireless transmission towers and burned through all that money also. Norm; > DC has many disadvantages. DC motors must have brushes, which are > maintenance intensive, a common point of failure, and a source of RF > noise, or have an internal inverter (such as used in "computer" fans) > to produce ac. DC cannot produce the rotating magnetic field used in > virtually all industrial motors. Reply; Many motors now, even some in washing machines and such like, are 'brushless' DC motors. And the fact that DC motors need to commutate or rectify power is not a problem with todays semiconductors that have a better conductivity that solid copper! The fact is that both AC and DC have advantages and disadvantages, depending on application. Some of the most efficient, compact, and most powerful motors in use today are DC permanent magnetic motors. One big advantage to using DC here is the ability to control the impeadence of the motor much more precisely than could be done with AC, which means less loss (and less heat). Another big advantage of DC motors is that in general they can have a much wider speed range, so a transmission may not be needed. Better control of torque throughout their range yields a smoother motion, where that is important. The biggest dis-advantage of brushless DC motors it that they cost significantly more and controllers can also be a bit more expensive. I would add, that if we ever do get a true 'energy super-highway' or that is a nation wide power transmission grid capable of sending humongous amounts of power across the continent from wind and solar production points for example to consumption points when and where needed, a critical part of that new grid will be DC transmission lines. This will allow small suppliers to connect on or off grid very fast without the cumbersome processes needed today and go a long way to make the grid more stable than it is now. It will also mean greater efficiency than AC transmission. In the future it may well be AC that is relegated to the back seat! -Ken _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
