My understanding of the terminology is that the yoke holds the pole
pieces together and is often part of the frame or casing, so the
answer to your question is no.
In a "normal" motor, the armature windings are wound around a core
which gives the armature greater momentum and thermal mass.
A coreless motor literally has no core. The armature is simply the
windings. The lower mass means they can respond much more quickly to
changes in voltage. The lower thermal mass is one reason they are said
to be unhappy when fed too low a frequency of pulsed waveform.
Purpose is technical. They have very low interia, no cogging. They are the
engineering choice for expensive (thousands to millions of pounds) precision
instruments where such behaviour is required. They have some uses in model
railway propulsion, if married to appropriate gearing.
Design. In most cases, the armature is just a wire basket, there is no
central "core" to the motor. This is what gives it the low inertia. In some
designs, the fixed magnet is placed within the centre of the basket. The
winding basket design means there are no specific "poles", so the motor does
Years ago, I edited a short work on making ones own motors, which covered
"normal" and "coreless" designs. I might translate it for the internet
sometime, though its value is only historical, as cheap quality small motors
are available commercially.
Webmaster at http://www.2mm.org.uk/
I have a Wills (yes, Wills, not SEF ;-) ex-SECR H class kit that I built
back in the late 80s, and it has a Portescap RG4 in it. When I run it (which
is not very often at the moment) it is very smooth. I'm wondering how best
to convert it to DCC though. What would be the motor settings on a Lenz Gold
to best suit??
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