On Thu, 10 Jan 2008 20:23:22 -0600, Rick Fochtman wrote: >--------------------<snip>--------------------- (John Eells) > >> True at the high end only. e.g., 168s used MGs because they used >> 415Hz power but 158s did not; they just used regular old 3-phase 60Hz >> 220V power. >> I was accustomed, decades ago, to hearing "400 Hz." Was it always 415 Hz., subject to verbal shorthand? "A" on a Baroque oboe? 0.4 KiHz? (Never mind!)
>> I never did know why, though. I always wondered whether it was to >> keep the number and size of power supply capacitors to a reasonable >> minimum. > >-----------------<unsnip>-------------------- >Transformers for 415 Hz are also much smaller and lighter than those for >the equivalent worload in 60 Hz. power. > (Important for aviation applications.) In fact, full-wave rectified 3-phase has <20% ripple with no filtering whatever (ignoring glitches). Almost good enough. Thoughts: o With more poles on the MG, one could get even higher frequencies. o With more windings on the MG, one could get more phases, probably even better than higher frequencies. o Why transformers? This is a specialized, dedicated application; use multiple taps on the generator (presumably stator) winding. All non-electrician's conjecture. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
