Re: what is the max bus voltage, 300V?

[Lee Hart <leeahart@earthlink.net>]

Rod Hower wrote:
> One thing that is a problem with sepex motors is the inability to
> change brush advance. This is a big problem when operating over a
> wide torque speed curve and a bigger problem when you try to regen
> (when the brushes would rather be at a different orientation than
> motoring) ... I would like to compare how a sepex design without
> moveable brushes can match the performance of an AC system.

In the early days (1900s), DC motors had movable brushes to optimize
commutation. By the 1920's they had figured out why the optimum brush
position moved (armature reaction), and devised compensating windings to
eliminate the effect. So when you look at any "state of the art" DC
motor after about 1930, it will have interpoles (smaller poles in
between the main poles), and face windings (winding set into the faces
of the main poles). When the designers get the position and number of
turns "just right", then optimum brush timing does not change with load
current, direction of rotation, or motor/generator operation.

The old aircraft starter-generators are an example of such a motor.
Though rated at 30v 500amps, I routinely ran mine at 72v 1000amps with
relatively little arcing!
--
Lee A. Hart                Ring the bells that still can ring
814 8th Ave. N.            Forget your perfect offering
Sartell, MN 56377 USA      There is a crack in everything
leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen