Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-02-05
2003-08-05
Mullins, Burton S. (Department: 3729)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S179000, C310S180000, C310S208000
Reexamination Certificate
active
06603234
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a winding for electrical machines wherein a number of conductor elements are fitted on a winding former, a winding for an electrical machine having a large number of conductor elements which are carried by a winding former and form a number of turns, and an electrical machine.
2. Description of the Related Art
Electrical machines, such as synchronous machines, have slots in which one or more current-carrying windings are placed. The slots with the windings can be located, for example, in the stator or else in the rotor of the electrical machine. During operation of such electrical machines, however, a non-uniform current distribution can in certain circumstances occur across the copper or conductor cross section in the slots. The slot height as well as the frequency of the current are significant factors in this case.
The non-uniform current distribution or one-sided or two-sided current displacement occurs in particular in large machines with bar windings and in the rotor bars of asynchronous squirrel-cage rotors. However, current displacement can also occur in the stators of small machines, for example if they are operated at high frequencies in order to achieve better utilization. These frequencies may be more than two kilohertz, with the operation of such electrical machines being made possible by modern converter technology.
In asynchronous motors, the effect of the non-uniform current distribution is advantageously used to increase the rotor resistance during starting, when a high slip frequency occurs.
Owing to the increase in the resistive heat losses, the current displacement is undesirable. Attempts have therefore been made to suppress the current displacement in windings through which alternating current or a current which changes with time flows during operation.
Various measures for suppressing current displacement are known, such as subdividing the conductor into parallel conductor elements, thus resulting in smaller conducting heights for the same conductor width. In this case, conductors located one above the other may have different conductor heights. Owing to the stray flux linking between the conductor elements, subdivision into parallel conductor elements generally does not lead to adequate suppression of current displacement.
In order to suppress the current displacement more effectively, attempts have therefore been made to form the conductor elements into layers. In the process, the sequence of the conductor elements in the slots is changed. In the case of two-layer windings, this results naturally as a consequence of the end winding design. Owing to the change in the sequence of the conducting elements in the slots, the integration path which governs an eddy current path has comprises field elements in opposite directions. This means that the individual flux elements partially compensate for one another, and the resultant flux linking becomes less.
Synthetic bars result in the stray flux linking within the slot area of an electrical machine formed from any two conductor elements disappearing completely. Such synthetic bars are subdivided conductors whose layers within the slot region are configured such that the flux linking of every possible eddy current path passing through the conductor elements disappears.
One known synthetic bar is the transposed conductor which is illustrated in
FIGS. 2
a
and
2
b
. In this bar, the conductor elements uniformly pass through all the height layers in a slot and leave the slot in the same height layer in which they enter the slot.
DE 197 54 943 A1 describes a double transposed conductor for the winding of an electrical machine, in which conductor elements are arranged in a number of adjacent stacks. Two adjacent conductor elements are in each case routed as a conductor element pair alongside one another over the entire length of a conductor, and are twisted as they do so. To achieve the desired twisting, the conductor elements are not only bent parallel but are also bent to be crossed over, in order to achieve optimum compensation for the transverse and radial fields during operation of the electrical machine.
The known synthetic bars including transposed conductors have the disadvantage, however, that they cannot be produced using modern automatic winding machines. Furthermore, the frequent crossing over of the conductor elements in the slot area, with the conductors being routed obliquely, leads to greater conductor element lengths and to poorer copper filling factors in the slot.
SUMMARY OF THE INVENTION
The object of the present invention is thus to specify a method for producing a winding for electrical machines which can be carried out more easily and by means of which a winding with an improved filling factor and adequate suppression of current displacement can be achieved. Furthermore, it is intended to provide a winding for an electrical machine, and an electrical machine, in which, during operation, current displacement is adequately suppressed, and which winding can also be produced by machine with a high filling factor.
This object is achieved by the method for producing a winding for electrical machines wherein the conductor elements (L
1
, L
2
, L
3
) are aligned parallel to one another in a predetermined order while being wound onto the winding former and, while being wound, the predetermined order is reversed in at least one place on the winding former. Advantageous features, aspects and details of the invention are evident from the description and the drawings. Advantages and features which are described with reference to the method likewise apply to the apparatus, and advantages and features which are described with respect to the apparatus likewise apply to the method according to the invention. Analogous statements apply to the electrical machine.
In the method according to the present invention for producing a winding for electrical machines, a number of conductor elements are fitted on a winding former, with the conductor elements being aligned parallel to one another while being fitted onto the winding former, and with the parallel-aligned conductor elements being reversed at least once, for example jointly, while being fitted, so that, at least in places, they change their position on the winding former. It is thus possible to produce a winding with a high filling factor, in which case, furthermore, the winding can also be produced by machine, and by means of which current displacement is effectively suppressed during operation of the electrical machine.
The conductor elements are advantageously placed in a slot, with the conductor element which is located deepest in the slot being located furthest upward after reversal. It is thus possible to produce windings in the slots of electrical machines, in which windings the current displacement during operation is particularly low.
The conductor elements are preferably fed by means of guide elements, in particular by means of wire guide nozzles. The guide elements or wire guide nozzles are rotated through 180°, for example in order to reverse the conductor elements during the winding process. A number of parallel wires are thus fitted, for example, onto a rotating winding former, thus producing a winding with a specific number of turns, and at a defined feed rate.
The parallel alignment and the wires or conductor elements placed parallel alongside one another result in a particularly high copper filling factor which may be, for example, up to 20% greater than in the case of conventional winding production. The reversal of the conductor elements, or the rotation of the wire guide nozzles through 180°, results in the conductor elements being reversed in layers. This results in uniform stray flux linking of the conductor elements, and thus also uniform current distribution between the conductor elements, the number of which is governed, for example, by the number of wire guide nozzles.
The reversal of the conductor elements is preferably in
Grau Edmund
Heyden Marcus van
Richter Matthias
Tareilus Alfred
Cohen & Pontani, Lieberman & Pavane
Mannesmann Sachs AG
Mullins Burton S.
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