Method for Winding the Stator in a Three Phase AC Machine

The present invention relates to a method for winding the stator of a three phase AC machine. In particular it relates to a winding method suitable for machine winding of the stator of an AC generator.

Methods are known by which a two layer winding is manually wound onto the stator of an AC generator. However machine winding of generators having relatively small stator inner diameters and a high number of grooves is generally not possible because first the lower layer of all coils must be wound and inserted into the grooves and only then can the upper layer be inserted. Since the upper layer is within the internal space of the stator, it is in the way when the lower layer is inserted. Further, in AC machinery with a small internal diameter there is not sufficient room for accommodating the inserting mechanism of an automatic winding machine. In known machine winding methods, the coils for the different phases are inserted into the grooves of the stator as single windings in the sequence in which the electrical phase angle of 120.degree. exists between sequentially wound windings. In this method, cross-over points for the winding ends result and further, the insertion of a subsequent winding is hindered by the already present preceding winding.

It is an object of the present invention to furnish a winding method in which the coil or winding ends do not interfere in the winding process. It is a further object of the present invention to furnish a winding method in which a particularly high space utilization factor results for the grooves of the stator. Briefly, in accordance with the invention, in a three phase AC machine having a plurality of poles and a stator having a predetermined number n grooves per pole and phase, a first winding is wound from a first starting groove to a first end groove and a wire end is furnished near said first end groove. A second winding is wound starting at a second groove adjacent to said first groove and ending at a second end groove adjacent to said first end groove. Again, a second wire end is supplied near said second end groove. A third winding is wound starting at a third starting groove adjacent to said second groove and ending at a third end groove adjacent to said second end groove. A third wire end is created near said third end groove. The starts of the winding at said first, second and third groove and said first, second and third wire ends are then electrically interconnected in such a manner that the start of the second winding and the second winding end are electrically interchanged. In a preferred embodiment distributed windings are used in order to increase the space factor for the grooves and to create an even better arrangement of the coil ends.

FIG. 1 shows the voltages induced in each winding of a three phase AC generator as a function of angle of rotation;

FIG. 2 is a schematic diagram showing the construction of an AC generator;

FIG. 3 is a winding diagram of a known winding method;

FIG. 4 shows a three phase winding connected in a Y connection; and

FIGS. 5-7 show a first, second and third embodiment of a winding method of the present invention as applied to a three phase 12 pole AC generator.

FIG. 1 shows the variation of voltage induced in each of three windings as a function of the angle of rotation of the stator. As is well known, an angle of 120.degree. exists between the individual phases.

FIG. 2 shows the construction of a 12 pole three phase AC generator. The number of poles 2p is equal to 12, and the number of grooves per pole and phase n is equal to 1. For a three phase AC winding the number of phases m equal 3. The number of grooves N is thus N equal 36. As shown in FIG. 2, the first winding is started at groove 1. Specifically, a winding 40 whose winding start is designated by the letter u is inserted into groove 1, a winding 41 whose winding start is denoted by the letter v is inserted into groove 3 and a winding 42 whose winding start is denoted by the letter w is inserted into groove 5. FIG. 3 shows the winding diagram corresponding to this known method. The start of the first winding 40 is denoted by u, that of the second winding 41 by v and that of the third winding by w. Winding end x of the first winding is in groove 34, the winding end y of the second winding in groove 36 and the winding end z of the third winding in groove 2. An electrical phase angle of 120.degree. results between the individual conductors of the three phase winding. The individual windings are then connected as desired, for example in a known Y connection as shown in FIG. 4. Specifically, winding ends x, y, z are connected at a common point. The winding diagram shown in FIG. 3 is disadvantageous for machine winding, because the winding ends interfere with each other and thereby cause the space factor for the individual grooves to be very low.

A more advantageous winding method and one which is easier to carry out on a machine is shown in FIG. 5. In this winding diagram in accordance with the present invention, a first winding is inserted in groove 1. The start of the first winding is denoted by the letter u. This strand is then wound through groove 4, etc. The winding end of the first winding is in groove 34. Thereafter a strand is inserted into the second groove 2 and wound until it ends at groove 35. Finally, a strand is inserted in groove 3 and wound to end at groove 36. The start of the winding inserted in groove 3 is v, the end of the strand ending at groove 36 is y. If now the strand starting in groove 2 is considered, it will be noted that a phase angle of 120.degree. relative to the other two phases will result if the ends of this second winding or strand are interchanged, that is if the winding start is considered at groove 35 (and is therefore denoted by w) while the winding end is considered the end in groove 2 which has the designation z. With this electrical interchange, each of the three windings has an electrical phase angle of 120.degree. relative to the other two. The winding diagram shown in FIG. 5 results in a process wherein the coil ends do not interfere with each other during insertion of the windings. This allows the space utilization factor to be substantially increased.

If a distributed winding is used, a further improvement in winding ease and in the space utilization factor results. For this purpose, a first partial winding is wound starting at groove 1, the winding continuing in the direction of increasing groove numbers from u.sub.1 to x.sub.1. Next, starting in groove 2 and winding in a direction with increasing groove numbers, a second winding is wound from z.sub.1 to w.sub.1, while the third partial winding starting in groove 3 is wound from v.sub.1 to y.sub.1. After this first group of partial windings has been inserted, a second group of partial windings is wound and inserted into the grooves as shown in FIG. 5. The insertion of the windings for the first phase of the second group of windings starts in groove 4, the winding taking place from x.sub.2 to u.sub.2. Thereafter the second partial winding is started in groove 5. The winding proceeds from w.sub.2 to z.sub.2. Finally, the second partial group for the third phase is wound starting in groove 6 and proceeding in the same direction from y.sub.2 to v.sub.2. It will be noted that the winding direction for the first, second and third groups of partial windings is the same, that is in the direction of increasing groove numbers. The phase angle of 120.degree. between individual phases is again achieved by interchanging the end terminals of the middle winding.

The coil ends are then connected as follows: u.sub.1 is connected to u.sub.2 to yield end u; v.sub.1 is connected to v.sub.2 to yield end v; w.sub.1 is connected to w.sub.2 to yield end w. For a Y connection, the coil ends x.sub.1, x.sub.2, y.sub.1, y.sub.2, z.sub.1, z.sub.2 are all interconnected to constitute the center point of the Y. The distributed winding diagram shown in FIG. 6 illustrates a method which yields a particularly high space factor for the grooves of the stator. The individual coil ends of the windings are arranged next to each other similarly as in a two layer winding without interfering with each other either during or after insertion. It is a further advantage of the method illustrated by the diagram of FIG. 6 that the winding takes place in the same direction throughout. This advantage compensates for the slight disadvantage which results from the fact that 12 winding ends must be electrically connected to each other.

The disadvantage of having to connect the 12 winding ends to each other can be eliminated by the method shown in FIG. 7. If the method illustrated in FIG. 7, the individual windings of the different phases are wound simultaneously. That means that the first group of partial windings is wound simultaneously, starting, respectively, in grooves 1, 2 and 3. After the winding of this set of partial windings has been completed, a second group of partial windings is wound in the opposite direction and inserted into the corresponding grooves, the winding ends appearing in the fourth, fifth and sixth grooves. Again, the ends z and the start w of the second winding are electrically exchanged thereby creating a phase angle of 120.degree. between the individual partial windings of each group. In the embodiment according to FIG. 7, the coil ends do not interfere with each other either in the inserted condition or during insertion. Here, too, a particularly high space factor results, allowing a higher power output for a machine having the same dimensions as known machines utilizing the previously known winding method.

The winding methods described above are in principle as applicable to a lap winding as they are to a wave winding. However, for manufacture on automatic winding machines, the wave winding has been found particularly advantageous.

While the invention has been illustrated for a 12 pole machine, the same principle applies to AC machines having any other number of poles, the distance between "adjacent" grooves always being equal to the number of grooves per pole and phase. For example if the number of grooves per pole and phase, n=2, grooves 1 and 2 belong together so that the set of grooves 1, 2 and the set of grooves 3, 4 together constitute adjacent grooves.

Various changes and modifications may be made within the scope of the inventive concept.