On Apr 11, 10:42*pm, Evan wrote:
On Apr 11, 1:32*pm, harry wrote:



Not he's got it right except for the fact that allr otating electric
lmachinary is AC.

I love how you can state that without any sort of qualification...

You seem to have forgotten about higher end bathroom fans
which use an inverter to operate a DC motor which is much
quieter than an AC motor...

AND

Light Rail vehicles are operated on DC systems which drive
HUGE traction motors with either an overhead wire or third
rail using the other rails as a one-way return path through
the vehicle chassis...

This is 600VDC and up, and WILL kill you if you make
any mistakes around it...

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

~~ Evan

All rotating machinery is AC. Some are fitted with a mechanical
rectifier/inverter called a comutator and brushes which ignorant
people somehow think run on a different principle. You need to get
into motor theory.

I don't know why you bring up rail traction. A hundred years ago
electrical traction was often DC transmission. However all this is
long abandoned even before the advent of semiconductors.
http://wiki.answers.com/Q/How_schrage_motor_works

Since the advent of semiconductors the efficiency and technology has
vastly improved
http://en.wikipedia.org/wiki/Inverte...equency_drives