On Wed, 22 Aug 2007 06:49:47 GMT, Ross Herbert
wrote:


You are right that the 3000 style as an AC type is rare, as there are
much better designs used for AC, but still using the same principle
of the divided magnetic path as Ron described.

Actually, I haven't found any description on AC relays which refers to
a "divided magnetic path", or anything remotely resembling this term,
so I doubt that it means anything at all. What I did find is a
description of the various types of shading ring (as refered to by Ron
and others) which might be found on AC relays and/or contactors meant
for 50/60 Hz operation. See page 36.
http://books.google.com/books?id=gES...sKmenpcNVhKamU


Ross page 36 does not seem to be relevant, however, your comment that
you find no reference to a divided path would indicate that you have
no idea what I have been talking about. You need to understand that
on an AC relay, the pole face is divided, and one section has the
shading ring around it, and the other section has no shading ring (so
that unshaded section it is just like you find on a DC relay). The
armature is therefore is attracted by the sum of the fluxes from each
of the two pole faces. The idea is that while the the coil is
energised, then even when the un-shaded pole flux is zero (twice per
cycle), there is still flux from the shaded (lagging or delayed) pole,
and so that there is no time during the AC cycle when there is zero
flux pull on the armature.

Peter Dettmann