The present invention relates to an end winding support for a rotor in an electrical machine, where the rotor consists of a lamination stack in which winding bars are arranged, distributed around its circumference, with the winding bars extending beyond an axial end of the lamination stack in order to form the end winding, and also relates to a process for installing a rotor winding with an end winding of this kind.
If the rotors of electrical machines are designed with bar windings, they are also subject to high centrifugal forces, particularly at high speeds. The rotor windings of variable-speed machines, for example, are often designed as bar windings. In particular, the machines in variable-speed pumped storage power stations are operated at high speeds and their bar windings are therefore subject to high centripetal accelerations. In the region of the rotor base there are usually groups of two winding bars arranged on top of one another in axial slots, as is sufficiently well known, and these are held in radial direction against the centrifugal force by means of slot wedges. In order to achieve the necessary connection arrangement and the required interspacing between the winding bars, the winding bars must be slanted away from the axial direction in the region of the end winding, where the winding bars in the top and bottom layers slant in opposite directions so that they intersect. Due to the complicated arrangement and geometry of the winding bars in the end winding region, it is not possible to hold them in slots with wedges in the same way as in the rotor base region. The end windings are subject to stress from the prevailing centrifugal forces as a result, which means that radial support is required for the end windings.
Furthermore, the end windings and the winding bars, respectively, in the region of the end windings must be cooled, as is also sufficiently well known. As a rule, cooling is effected via a gaseous cooling medium that is directed over the end windings.
Various possibilities for supporting an end winding are known from the state of the art. So-called retaining rings are common, which are usually shrunk onto the rotor base and rest on the rotor base as a result. An example of this is found in GB 378 920 A, where an outer ring with teeth is pushed through the rotor slots onto the rotor base and is then turned so that the teeth come to rest between two slots, thus blocking the axial mobility of the outer ring. This outer ring supports the end winding in radial direction against the centrifugal forces. A similar arrangement is shown in GB 1 474 439 A, where two rings are shrunk on outside round the end winding, but again rest on the rotor base in radial direction. The problem with such arrangements, particularly in electrical machines in the heavy duty range, is that ventilation slots arranged between the partial lamination stacks to cool the rotor are closed off by the retaining ring shrunk onto the rotor base, which interferes with cooling of the rotor base in this region.