Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-07-26
2002-05-14
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S206000
Reexamination Certificate
active
06388357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an armature winding for a dynamo-electric machine such as a two-pole, three-phase turbine generator. The present invention relates to, in particular, an armature winding for a dynamo-electric machine having three parallel connected circuits for each phase.
2. Description of the Prior Art
Normally, an armature winding in a high-capacity turbine generator includes upper coil pieces and lower coil pieces accommodated in upper and lower portions of the slots of a layered core, respectively. The upper coil pieces and the lower coil pieces are connected in series thereby increasing voltage generated at the pieces and the capacity of the generator. When the voltage of the armature winding increases, however, the thickness of the main insulating member of the armature winding increases, with the result that the cross-sectional area of a conductor portion of the armature winding decreases and current density increases so as to cause the increase of loss.
In addition, in an indirect cooling type machine for cooling an armature winding from the outside of the main insulating member of the armature winding, there is the possibility that the thickness of the main insulating member induces an increase in heat resistance of the armature winding, thereby disadvantageously increasing the temperature of the armature winding.
To avoid this disadvantage, while the capacity of a generator is kept unchanged, an armature winding is divided into a plurality of parallel connected circuits so as to decrease generated voltage, thereby decreasing loss and improving cooling capability. In a high capacity generator of indirect cooling type, in particular, it is ordinarily seen that the number of slots increases to increase the cooling circumference. It is, therefore, necessary to provide an armature winding having parallel connected circuits more than three parallel connected circuits.
When an armature winding having more parallel connected circuits than three parallel connected circuits is applied to a two-pole dynamo-electric machine, it is impossible to make the voltage generated at the respective parallel connected circuits completely the same. As a result, circulating current occurs between the parallel connected circuits so that the loss of the armature winding disadvantageously increases. To decrease the circulating current loss, it is essential to reduce the voltage unbalance between the parallel connected circuits as much as possible. To reduce the voltage unbalance between the circuits, it is necessary to specially arrange coils belonging to the respective parallel connected circuits in the respective phase belts.
For example, as disclosed in U.S. Pat. No. 2,778,963 to Rudolf Haberman issued on Jan. 22, 1957, it is necessary to arrange coils of the respective parallel circuits in the respective belts so as to minimize the deviation between the absolute values of the voltages generated at the respective parallel connected circuits and the deviation between phase angles of the respective parallel connected circuits so as to reduce voltage unbalance between the respective parallel connected circuits.
An armature winding of a two-pole, three-phase dynamo-electric machine normally has two phase belts per phase. Thus, by mutually connecting these two phase belts to cancel their counterpart voltage unbalance, voltage unbalance is reduced. However, when the number of slots is odd, the number of coils of the two phase belts do not coincide with each other, in a case of using the above-stated method, it is difficult to reduce voltage unbalance between the circuits. As an example of a method of reducing voltage unbalance in a case where the number of slots is odd, there is disclosed a dynamo-electric machine having 45 slots in U.S. Pat. No. 3,652,888 to Dean Harrington issued on Mar. 28, 1972. According to Harrington, the deviation of phase angles among the three parallel connected circuits is 0.13° to 0.14° . Judging from the standard set by Haberman that the deviation between phase angles is 0.15° or less, it is hard for Harrington to maintain sufficient voltage balance between circuits.
Furthermore, owing to reduce the voltage unbalance, the mechanical structure of the armature winding of Harrington is disadvantageously slightly complicated.
This is because, due to the irregular arrangement of coils belonging to the respective parallel connected circuits in each phase belt, it is necessary to provide a lot of jumper wires for connecting upper and lower coil pieces at each coil end.
To avoid interference between the respective jumper wires, and interference between the respective jumper wires and the connecting portions of the usual respective upper and lower coil pieces to the lead wires, excessive space is required in the dynamo-electric machine so that the length of the dynamo-electric machine increases. In addition, the workload required to connect the large number of jumper wires increases. Furthermore, since each of the jumper wires is longer than the usual upper and lower coil connection pieces, there is the possibility that reliability of the connection portions of the jumper wires and the lead wires is decreased.
SUMMARY OF THE INVENTION
The present invention is directed to overcome the foregoing problems.
Accordingly, it is an object of the present invention to provide a three phase armature winding of a dynamo-electric machine having three parallel connected circuits per phase, wherein two (first and second) phase belts of each phase are arranged in two (first and second) slot groups each having slots and a number of slots of the first slot group is different from a number of slots of the second slot group, which is capable of reducing the number of jumper wires at coil ends and reducing voltage unbalance between parallel connected circuits.
In order to achieve such object, according to one aspect of the present invention, there is provided a three phase armature winding for a dynamo-electric machine, in which the three phase armature winding is disposed in a core, the core having a number of slots, each phase of the armature winding comprising: a first phase belt for a first slot group having (3n+2) slots; a second phase belt for a second slot group having (3n+1) slots; three parallel connected circuits each constituting a number of series connected coils per circuit, each of the series connected coils per circuit having a first coil piece and a second coil piece connected thereto in series, each of the first coil piece and the second coil piece having one end portion and other end portion, the first phase belt housing (3n+2) series connected coils of the parallel connected circuits and the second phase belt housing (3n+1) series connected coils thereof, when the three parallel connected circuits in each phase are designated circuit numbers, respectively, the three parallel connected circuits in each phase being arranged so that a circuit sequence of the circuit numbers of the first coil pieces in each of the first and second phase belts and a circuit sequence of the circuit numbers of the second coil pieces therein are substantially the same; and a pair of connection members mounted at the other end portion side of the series connected coils in the first phase belt whereby part of the first coil pieces in the first phase belt and part of the second coil pieces therein are connected so that the circuit sequence of the part of the first coil pieces is interchanged with that of the part of the second coil pieces.
In preferred embodiment of this aspect, the three phase armature winding is composed of a two layer lap winding, each of the connection members is a jumper wire and the slots are arranged in sequence about a rotor of the core.
In preferred embodiment of this aspect, an arrangement position of each of the jumper wires is determined so that a voltage unbalance among the three parallel connected circuits is reduced and a phase of a highest voltage in voltages induced in the respectiv
Matsumoto Hisakazu
Tokumasu Tadashi
Dinh Le Dang
Kabushiki Kaisha Toshiba
Ramirez Nestor
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