Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-01-26
2001-03-13
Mullins, Burton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S195000, C174S033000
Reexamination Certificate
active
06201333
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention:
The invention relates to a method for producing a conductor bar of a stator winding for an electric machine, in particular a generator, with a stator as well as a rotor disposed rotatably therein. Each conductor bar is formed from component conductors which are made of conductive material, are situated one above another in pairs, traverse a stack from a top layer obliquely to a bottom layer and in each case have uniform cranks in the vicinity of the top layer and in a bottom region. The cranks of each two component conductors placed one above another and assigned to one another in pairs are disposed offset in the longitudinal direction at a spacing relative to cranks of a succeeding or preceding pair of component conductors. The component conductors are disposed in two stacks located next to one another and laterally adjoining one another. The component conductors are each situated one above another in pairs and in each case are mutually interlocked through the use of the laterally neighboring component conductors. As a result, each conductor bar extends partially on the surface of the stator facing toward and away from the rotor. The invention also relates to a conductor bar for such a stator winding which is produced according to the method.
It is known in the case of large electric machines, in particular of rotary machines such as motors or generators, which have a stator and a rotor rotatably disposed therein, for the windings disposed in the stator and in the rotor to be configured by using conductor bars with a large rectangular cross section made from electrically conducting material, such as copper.
In that structure, because of the large cross section per conductor bar required in each case, the individual conductor bars are formed from component conductors which are usually disposed in each case one behind another radially with interposed insulation in two stacks located next to one another.
In order to avoid, or at least to reduce an increase in resistance due to the displacement of current from the interior of the conductor to the surface thereof, the individual conductors are usually provided with uniform cranks which have the effect of causing each component conductor bar to run partly along the surface of the conductor.
In that regard, the word crank is understood as a double bending of the individual component conductor of a conductor bar which permits each individual conductor to be joined partly to the other component conductors inside the conductor bar in such a way that the component conductor runs alternately in one or the other, adjoining conductor stack. The individual component conductors are interlocked helically so that it can occur continuously. In that configuration, each component conductor runs in sections in the same relationship in the planes of the winding which is provided.
That possibility for reducing resistance has been successfully employed for a long time. However, it has now emerged that in the case of electrical machines of higher power, in which each conductor bar must have a relatively large current-carrying capacity, such interlocking or offsetting encounters limits of feasibility which can only be reached by a different dimensioning of the component conductors.
The result thereof, on one hand, is that when producing the component conductors for a conductor bar there is a specific need for space for the finished or offset component conductors, and that need results from the radius of curvature for the crank. On the other hand, the space available in the stator is insufficient for the volume required by the finished offset conductor bars. The consequence so far has been an increased outlay for production in order to nevertheless be able to install the conductor bars provided in the available space.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for producing conductor bars and a stator winding for an electric machine having correspondingly produced conductor bars, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and in which the outlay for production is reduced without disadvantages for electrical functioning.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing conductor bars of a stator winding in an electric machine, in particular a generator, having a stator and a rotor rotatable therein, which comprises forming each conductor bar by placing component conductors made of conductive material one above another in pairs, traversing a stack from a top layer obliquely to a bottom layer and each having uniform cranks in the vicinity of the top layer and in a bottom region; offsetting the cranks of each two component conductors placed one above another and assigned to one another in pairs in longitudinal direction at a spacing relative to the cranks of a succeeding or preceding pair of component conductors; placing the component conductors in two stacks located next to one another and laterally adjoining one another; placing each of the component conductors one above another in pairs and mutually interlocked by laterally neighboring component conductors, causing each conductor bar to extend partially on a surface of the stator facing toward and away from the rotor; and locating the cranks of the component conductors of a pair of conductor bars at a spacing from one another in the longitudinal direction to produce an interspace relative to the component conductor of the pair of conductor bars disposed therebelow.
With the objects of the invention in view, there is also provided a stator winding for an electric machine, in particular a generator, having a stator and a rotor rotatable therein, the improvement comprising conductor bars formed of at least three component conductors made of conductive material; the component conductors disposed in two stacks laterally adjoining one another in two planes located radially one behind another; the component conductors having uniform periodic cranks disposed at a spacing; the component conductors mutually interlocked, with each conductor bar running alternately partially on a surface of the stator facing the rotor; and the cranks of the component conductors of one of the conductor bars disposed in longitudinal direction at a spacing from one another forming an interspace relative to the component conductor of the conductor bar of the next plane disposed therebelow. The interspace accommodates the changes to the cross section of the component conductors which are caused by repositioning of material during offsetting.
In other words, the offsetting or interlocking technique that is already known to date, in which it is ensured that the periodic cranks which are disposed at a defined axial spacing in each component conductor connect without a spacing at the neighboring component conductor, is abandoned in favor of a new offsetting technique. In the new offsetting technique spacings are deliberately provided between the cranks of the neighboring component conductors, that is to say those situated one on another and assigned to one another in pairs. These spacings which are provided according to the invention produce interspaces that are used in order to accommodate the component conductors with the radii of curvature required for the cranks, and with the local cross sectional thickening necessarily associated herewith. This is done without requiring an additional outlay, or the occurrence of undesired straining of the conductor package.
In contrast with initially existing objections that these interspaces could have a negative effect on the electrical properties of the relevant electric machine provided therewith, practical trials have shown that there is no problem in achieving the targeted increase in power through the use of the inventive structure of the conductor bars.
An inventive stator winding is consequently formed from conductor bars in which each conductor bar
ABB Patent GmbH
Greenberg Laurence A.
Lerner Herbert L.
Mullins Burton
Stemer Werner H.
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