Re: Direct Drive Revisited

[XURQ03A@prodigy.com ( LEE A HART)]

> Torque converters, sprag clutches that's mechanical stuff aren't they?

Luckily (for us EEs), there is an electrical equivalent for most mechanical devices.

            transmission = transformer (with fixed taps)
        torque converter = variac (variable transformer) but with
                           high resistance winding (i.e. lossy)
            sprag clutch = diode (locks up to pass torque one way, but
                           spins free the other)

> Lets talk! I have designed production 1/8th HP PM PWM motor controls...
> As I also stated to Lee Hart, I work at Miller Electric welding equipment.

That's a pretty close field. Both EVs and welders have to handle high power,
and be pretty tough and reliable. Though one thing occurs to me; welders don't
care much about efficiency.

> ...I'd like having something simple rather then duct taped together!

But duct tape *is* simple! Perhaps you meant "reliable" instead of simple?

>> Another advantage to AC is inherant regen, whereas it is complex to
>> implement DC regen.

> I was thinking of a boost converter... not that complex. What am I missing?

All motors can be used as generators (i.e. do regen). The problem is that some
are easier to use than others. The series DC motor (most commonly used in EVs)
happens to be one type that is hard to use as a generator. To put it in
electrical terms, it has a negative resistance as a generator, and so is
inherently unstable.

A sophisticated controller can compensate, and do regen with a series DC
motor. However, most series DC motor controllers are not built for it.

If you want simple reliable easy regen, use a shunt or PM DC motor. Then the
controller problems for regen become simple. Though using it as a traction
motor becomes harder (nothing is ever free :-)

Lee Hart                     If you would not be forgotten
4209 France Ave. N.          Soon as you are dead and rotten
Robbinsdale, MN 55422 USA    Either write things worth the reading
phone (612) 533-3226         Or do things worthy of the writing
e-mail XURQ03A@prodigy.com   (Ben Franklin, Poor Richard's Almanac)