Re: is the magnetic field really moving?

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"blackhead" <larryharson@[EMAIL PROTECTED]
> wrote in message 
news:018bb8d6-1d5a-4622-8deb-23d004d5f217@[EMAIL PROTECTED]
 2 Sep, 20:14, phil-news-nos...@[EMAIL PROTECTED]
 wrote:
> On Mon, 1 Sep 2008 14:07:36 -0500 Terry L Hewett Sr 
> <terrylhewet...@[EMAIL PROTECTED]
> wrote:
>

He mentioned that it isn't new and is a gramme ring

http://en.wikipedia.org/wiki/Gramme_machine

I'm quite aware of the construction of a Gramme Ring machine- Terry's 
machine isn't one.

Note also that a Gramme Ring machine is a rather primitive DC machine 
(advanced in one respect in that it made more effective  use of  the 
windings  and of comutation than its predecessors- making it practical).
The 
Wiki article indicates that only one coil on each side was active- in fact

all the coils on either side except for the ones under the brushes were 
active. It was a continuous coil rather than separate coils as indicated
in 
the diagrams. However less than half of each turn was active so design 
changed (as indicated under the "modern form") to eliminate the interior 
conductors. This modern form is  not and never was (as far as I know but I

really only got to know the  details of DC machine design about 50+ years 
ago) called a  Gramme ring machine as implied in the article although it
is 
definitely recognized as the predecessor of modern DC commutator motors.

The Wiki article is misleading when it says "The Gramme machine used a
ring 
armature, i.e., a series of thirty armature coils, wound around a
revolving 
ring of soft iron. The coils are connected in series, and the junction 
between each pair is connected to a commutator on which two brushes run.
The 
permanent magnets magnetize the soft iron ring, producing a magnetic field

which rotates around through the coils in order as the armature turns."

This appears to imply that the ring moves independently of the coils and 
that there is a magnetic field rotating inside the ring. Not so. If you go

to the article from which  this statement is taken, ( 
http://chem.ch.huji.ac.il/history/gramme.html
)  there is a clear
schematic 
showing the fields and windings as well as somewhat better pictures The 
coils (attached to the ring) rotate through and transverse to the magnetic

field produced by the external field poles as shown (as in a modern 
machine).

-- 

Don Kelly dhky@[EMAIL PROTECTED]
 the X to answer