RE: DIRECT DRIVE REVISITED

[eric.chang@chrysalis.org]

Hi.  From what I have read, one of the major strengths of an AC motor
(or, equivalently, BLDC) is not that it is more efficient, but that it is more
reliable, or should I say, more predictable.  I was just reviewing
some Ford data on their ETR II prototype, and they had an interesting 
gra[h.  They were running it against a typical DC conversion,  and
it fell short in efficiency for all except the variable city driving
schedule (which, admittedly, is the most realistic).  Obviously,
the AC drive will perform much better under these conditions, since it has
regen.  Damon's recent post mentioned  stress fon DC motor and
associated drive line components.  The commutator problem is absent,
so there is greater opportunity for impedance matching.  But that kind of
silicon still costs more than gears, and it is not clear whether it is more
efficient as well.  Note for example, that one one would have
to also  account for motor aosses atlosses at the higher currents.
 
Eric