Fig. 268.
Fig. 269.
Fig. 270.
In order to secure an easier fit, the side bars E F, and end pieces, A B, are so cast that slots M are formed when the two parts are put together.
This machine possesses several advantages. For example, if we magnetize the cores alternately, as indicated by the characters N S, it will be seen that the magnetic circuit between the poles of each part of a casting is completed through the solid iron side bars. The bearings for the shaft are located at the neutral points of the field, so that the armature core is not affected by the magnetic condition of the field.
The improvement is not restricted to the use of four pole pieces, as it is evident that each pole piece could be divided or more than four formed by the shape of the casting.