Fig. 1,485.—Section of Western Electric stationary armature core showing laminations clamped in place, and ventilating ducts. The stator or stationary armature consists of soft iron laminations assembled in the magnet frame with stator coils embedded in the core slots. The laminations are punched separately and then carefully annealed to reduce hysteresis losses. After annealing, a coat of japan is applied, effectively preventing the flow of eddy currents in the assembled core. The frame is cast iron and of the box type construction. The frames of the smaller sizes are cast in one piece, while frames of the larger sizes are split to facilitate installation. Large openings are provided in the box type frame, in order to improve the ventilation. The laminations are securely held in place in the frame by heavy end rings and by steel clamping fingers which are firmly bolted to the frame. The outer circumference of the core is dovetailed to the frame, and the inner circumference is slotted to receive the windings. The alignment of the slots is insured by means of metal wedges, and no filing is done on the slots, so that each lamination is always insulated from the next one. Numerous ventilating ducts allow the free circulation of cool air through and around the coils. The open slot construction is employed and the coils are fitted into insulating troughs which offer excellent mechanical and electric protection. The coils are held in place by suitable wedges.
8. With respect to the shape of the coil ends, as:
- a. Single range;
- b. Two range;
- etc.
In addition to these several classes of winding, there are a number of miscellaneous windings of which the following might be mentioned:
- a. Chain or basket winding;
- b. Skew coil winding;
- c. Fed-in winding;
- d. Imbricated winding;
- e. Mummified winding;
- f. Spiral winding;
- g. Shuttle winding;
- h. Creeping winding;
- i. Turbine alternator winding.
Fig. 1,486.—Method of assembling form wound coils. The picture shows a section of a General Electric armature with part of the coils in place. A layer of insulating material is first placed in the slots, before inserting the coils as seen at the left. When the coils are in place and surrounded by this layer of insulating material the retaining wedges are inserted in the notches, thus closing the slots and protecting the coils from mechanical injury. A few wedges are seen in position at the right.