Re: Steam power
- I would like to hear from an electrical engineer about this starter
question Pat. I was taught in school that a series wound motor under
no load would wind up and self destruct. Now I do not know much
about winding motors. I have forgotten most of what I knew also but
I am wondering if some starter motors have any - either compound or
synchronous windings. It probably would be better, knowlage wise,
for me to ask - Does any starter motors have any other type of
winding included with their series windings to limit their top
r.p.m.? In my opinion that would be the only way a starter motor
could be used for such below potrayed use. That is, unless the
voltage could be electronically controlled, say, in the manner of
vehicle "day running head-lights" where the voltage is controlled
with a false A. C current. For use on the starter I don't know but
it might have to be rectified after that. This would take the place
of a variable resistance to control the speed (reostat ???) so
current would be limited by cutting the voltage without the heat-
loss of the variable resistance.
--- In firstname.lastname@example.org, Pat Delany <rigmatch@...> wrote:
> How little I know!
> I am hooked on the idea that grinding should be a
> major part of MM operation. I can't machine a decent
> finish on lot of the steel scrap that I collect and I
> suspect that I am not alone. My personal answer has
> been to rough the piece out and finish it to size with
> an air powered tool post grinder that I built. Is a
> small starter motor a practical power source for a
> tool post grinder?
> -- stinkfoot151 <stinkfoot151@...> wrote:
> > Starters are series wound DC motors, meaning that
> > the current they
> > consume when stalled...and therefore the torque
> > developed when
> > stalled is extremely high. If allowed to free run,
> > the starter will
> > wind up to a certain RPM where its back emf...or
> > internal generator
> > so to speak...creates enough reverse voltage to
> > limit current to only
> > that required to overcome friction while spinning at
> > that free
> > running high RPM.
> > This doesn't address the bearing overheating problem
> > due to high RPM
> > though. Maybe a modified starter with ball or
> > roller bearings would
> > be practical.
> > My point is, given the proper bearings and if the
> > starter is
> > relatively lightly loaded and allowed to spin up to
> > a somewhat high
> > RPM. Heating due to current draw will not be an
> > issue. My guess
> > would be to load it down while monitoring
> > temperature which should
> > stabilize at some combination of torque, RPM, and
> > voltage. Brush
> > wear will be less here too since less current is
> > being drawn by the
> > motor.
> > --- In email@example.com, "David G.
> > LeVine" <dlevine@>
> > wrote:
> > >
> > > At 03:25 PM 7/2/2007, you wrote:
> > >
> > > >On 7/2/07, Pat Delany
> > <<mailto:rigmatch%40yahoo.com>rigmatch@>
> > wrote:
> > > > > Honestly, the only practical use for a starter
> > motor that I can
> > think
> > > > > of is to use it for a temporary speed reducer
> > like in the book.
> > As for
> > > > > steam, I shudder at the fuel consumption in
> > areas where it
> > takes much
> > > > > of the day to find twigs for fuel to cook
> > dinner.
> > > >
> > > >Solution: water cool the starter, use the steam
> > to power another
> > > >station, and cook your food with the excess heat.
> > > >
> > > >(joke)
> > >
> > > Actually, I just looked at the Advance Auto Parts
> > catalog. Did you
> > > realize that starters now run 3 HP or more and
> > come with a 4.4:1
> > gear
> > > reduction units? That means 2.2 KW input at 100%
> > efficiency. That
> > > WILL get hot in a hurry.
> > >
> > >
> > > David G. LeVine
> > > Nashua, NH 03060
> > >
> Yahoo! oneSearch: Finally, mobile search
> that gives answers, not web links.
- At 12:46 AM 7/4/2007, you wrote:
>OK. I am an electrical and mechanical engineer. Or at least those are theMy field is electrical -- electronic to be specific, but I played
>fields in which I am degreed and have experience.
>A series wound motor _could_ spin to self-destructive speeds, but
>other losses usually limits the ultimate speed. If there is a
>possibility of a
>motor running unloaded, the design will include sufficient
>resistance to limit
>the maximum speed to that which the mechanism can withstand.
with cars a lot. One issue is that starters had soldered connections
which melt and spray metal when they get too hot.
The new PM starters will generate back EMF when unloaded and won't
spin as fast, which LIMITS the probability of self destruction. Of
course the bearings can become warm if this keeps up too long, and
that is not my field of expertise.
David G. LeVine
Nashua, NH 03060