The impellor and magnet turn as the pump head creates a magnetic field that
attracts / repels the magnet attached to the impellor.

I don't know enough to tell if they switch multiple coils to create a
rotating field or it is just the ac power fed to it which as Alternating
current swings from (in our 240 volt 50 Hz system here in New Zealand) from
+120 to -120 and back 50 times a second creates a series of magnetic swings
surrounding the magnet on the impellor.

Does that make sense? - not an easy thing to explain without pictures....


wrote in message
oups.com...

Richard wrote:
My experience is not with the Eheim pumps, but their canister filters.

The ceramic rod through the impellor assembly should be one piece. it
fits
(on my filters anyway) into a cylindrical rubber "bearing" at each
end -
this holds the shaft steady and centered. The shaft does not turn.

The coil in the pump head makes the magnet spin on the shaft. As the
impellor can only turn about 180 degrees on the magnet it turns with it
and
hence pumps the water.

.


Richard - thanks for the reply.

"The shaft does not turn" - the impeller is attached to the impeller
shaft. iI the impeller shaft does not turn, what causes the impeller to
rotate? - MIke