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Pastimes : From A to Zeev" -- SI Sacks Zeev -- Ignore unavailable to you. Want to Upgrade?

To: Zeev Hed who wrote (657)	12/4/1999 10:18:00 AM
From: Mark Johnson	Respond to of 708

<<why is Lev leaving just before harvesting the fruits of his persistence?>>> You know the above comment is the same kind of negative spin you've put on the Valence thread...The comments you've been criticized for.... Everyone knows that Lev's stay was for 18 months or so (and you know damn well). He has always maintained his return was temporary until he got the company up and running.....It's shameful for you to keep up the negative spin.....I detect a little sour grapes on your part...

To: Zeev Hed who wrote (657)	12/26/1999 10:17:00 AM
From: long-gone	Read Replies (1) \| Respond to of 708

Dr., I'm hearing stories(even from friends in the electrical generation world) about the windings in both generators & motors becoming aluminum with silver sheathing or straight silver. These seem to be coming from both the "normal" and the super-conducting sides of the industry. a quick search led me to this which speaks of silver sheathing on aluminum windings: (Is there something "new" about which we should know?) Performance of High Temperature Superconducting Coils for Implementation into Megawatt Class Generators* A. J. RODENBUSH and S. J. YOUNG American Superconductor Corporation, Westborough, Massachusetts, USA Abstract--The United States Air Force and Ballistic Missile Defense Organization are developing a 1-Megawatt exciter/ generator for airborne applications. The exciter is constructed with an eight pole external field winding and rotating hydrogen cooled armature with integral rectifier. The exciter was originally designed with high purity aluminum field coils cooled with liquid hydrogen. The United States Air Force is presently investigating the potential for replacing the aluminum field coils with high temperature superconductor (HTS) field coils cooled with hydrogen. Eight HTS race track shaped field coils were built with BSCCO-2223 tapes for operation at 20K. They were constructed to be consistent in geometry with the aluminum coils. The electrical performance of the HTS coils exceeded the required 72,000 ampere-turns at the 1-microvolt per centimeter electric field criteria. This paper reviews the design, construction and testing of the field coils and discusses the potential of this technology for airborne applications. * Research supported by United States Air Force AFRL/ PRPS and BMDO Science and Technology Office. INTRODUCTION The Wright Patterson Airforce Base (WPAFB) has been developing lightweight high power density generators since the early 1970?s for airborne applications. The work began with the development of a high-speed superconducting generator1 employing low temperature superconducting (LTS) windings for the rotor. The stator employed water-cooled copper winding operating at very high current densities. Concerns such as vacuum integrity for cryogenic insulation at 4.2K and the fragile nature of the rotor due to extensive thermal and magnetic shields necessary for protection of the LTS windings led to the development of hyperconducting aluminum windings2, 3 for both the stator and rotor which were cooled to 20 K with liquid hydrogen. This produced a fairly compact and robust machine that did not require extensive thermal and magnetic shields. In recent years, high temperature superconductors (HTS) development has provided impetus for the replacement of the aluminum rotor magnet poles with HTS poles4. Like the hyperconducting aluminum machine3, the HTS machine can operate above 21 K and would not require elaborate thermal and electromagnetic shields. The HTS generator can deliver 1 MW if each pole develops 72,000 A-turns4. This paper discusses the design and construction of HTS magnet poles for this generator. (cont) amsuper.com Zeev, I'm hearing claims of improving efficiency by 30%.