[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: gEDA-user: Calculating a linear self excited induction generator


On Jun 11, 2006, at 3:40 PM, Samuel A. Falvo II wrote:

On 6/11/06, Karel Kulhavy <clock@xxxxxxxxxxxxx> wrote: 
I read about self excited induction generator, homopolar generators,
liquid metal dynamos, interstellar plasma dynamos, linear motors
and electric meters.

Ummm . . . Interstellar?!

Sure. That's where the galactic magnetic field comes from. Natural dynamos are common in the universe: there's lots of conductive stuff in electrical contact and in differential rotation.

About 3 years ago I heard a talk by Roger Blandford on the electromagnetic physics of stellar collapse forming a black hole. The dynamo saturation condition for the accretion disk a few seconds after the initial collapse suggests there should be zetavolt potentials driving exaamp currents around! Roger tweaked his physicist audience by using SI units rather than the Gaussian units physicists usually use: after all, he was analyzing the star as electrical machinery. The only trouble is that the SI doesn't define prefixes high enough to handle the power (something like 10^42 watts)! That power can make a gamma ray burst that's still intense enough to be detected by an instrument you can hold in your hand after traveling 10 billion years!

I expect to use gEDA to design the electronics for a new generation gamma ray burst detector starting later this year.


I got an idea of placing two coils almost touching the aluminium rim and
wiring them somehow obscurely with capacitors (how people do in wind
power plants with squirrel cage motors nobly relabeled as "self excited
induction generators") so they would prime themselves and start
generating. If it works with cyclic asynchronous motor it should work
with a linear one too, shouldn't? 

In what way is it self-priming?  Given a large enough, flat plate
dynamo, I'm sure one could exploit the Earth's natural magnetic field.
But, a small dynamo the size of which is suitable for a bike would
never have sufficient surface area for electrical generation, no
matter how fast it's made to spin.

Remember that energy is neither created nor destroyed -- if it's
self-generating, it has to draw energy from somewhere.  Traditional
alternators draw this energy from shaft rotation.  Where is the
self-excited generator drawing its energy from?

Dynamos convert mechanical energy into electromagnetic energy. In a dynamo, there is positive magnetic feedback, so any tiny seed field will build up until it reaches a saturation level determined by the structure and operating conditions of the dynamo. The seed field magnitude doesn't matter. But dynamo design is tricky: you really have to understand and use Maxwell's equations. The network theory we use for circuit design won't get you there.

John Doty              Noqsi Aerospace, Ltd.
jpd@xxxxxxxxxxxxx


_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user