Data processing: structural design – modeling – simulation – and em – Simulating electronic device or electrical system
Reexamination Certificate
2000-06-16
2001-11-27
Mullins, Burton S. (Department: 2834)
Data processing: structural design, modeling, simulation, and em
Simulating electronic device or electrical system
C310S180000
Reexamination Certificate
active
06324494
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electric motor modeling and, more particularly, to a method and system for approximating the end-turn leakage reactance associated with the stator windings of an electric motor for use in modeling the performance of the motor to facilitate testing of the motor design.
BACKGROUND OF THE INVENTION
Electric motors for use in particular applications typically must be designed to achieve particular performance characteristics, such as speed and torque output for a predetermined load and operating conditions, for example, and to satisfy particular physical constraints, such as motor size and weight, for example. Of course, in designing motors, efforts are also made to minimize the cost as much as possible. When a motor is designed for a given application, testing must be done to ensure that the designed motor meets whatever performance requirements and physical constraints may be specified for that application. However, it is costly to build an actual motor to test the underlying design for compliance with the specified performance requirements and physical constraints and then to refine the design, if necessary, and construct a new motor, sometimes repeatedly, until the final design meets the specified performance.requirements and physical constraints. To avoid some of the cost associated with such construction and testing, modeling techniques have been employed to simulate the performance of new motor designs, using digital computers, for example, to test whether such motor designs comply with specified performance requirements and physical constraints.
While the problem of modeling or simulating the performance of an electric motor is quite complex, prior modeling systems have simplified the problem by making assumptions about the structure and performance of the simulated motor to reduce the amount of computation required to model the motor. Those assumptions oversimplify the problem, however, and the prior modeling systems produce inaccurate simulation results in some cases and are less valuable because they do not accurately represent the performance of the actual motor.
SUMMARY OF THE INVENTION
The present invention generally relates to a method and apparatus for developing a more accurate approximation of the flux leakage reactance of the end-turn bundles of the stator windings of an electric motor, based on a discrete representation of the distribution of the turns of the coils of the stator winding for use in modeling the performance of the motor.
According to one aspect of the present invention, an end-turn leakage flux approximation is developed for turns of coils of a stator winding of an electric motor having a stator with a predetermined number of stator slots within which the turns of the stator winding are distributed according to a predetermined distribution. The stator winding includes at least two stator poles, and the end-turn leakage flux approximation is derived by developing a first indication representing a pole-to-pole permeance based on an approximated leakage flux path linking two poles, developing a second indication representing an individual pole permeance based on an approximated leakage flux path linking one pole, and combining the first and second indications to produce the end-turn leakage flux approximation, wherein at least one of the first and second indications is developed in accordance with a discrete representation of the predetermined distribution of the turns of the stator winding.
In some embodiments, one or both of the first and second indications may be based on: (1) the radial positions of the stator winding turns in respective stator winding slots; (2) the extent of distortion of the predetermined distribution of the stator winding turns from sinusoidal; (3) the order in which multiple stator windings are wound on the stator; and/or (4) the number of slots in the stator. Further, where the electric motor includes a plurality of stator windings, the first and second indications may represent respective permeance totals for all of the stator windings.
According to another aspect of the invention, at least one of the first and second indications may be developed by combining permeance contributions of a plurality of portions of the stator winding. In some embodiments, the plurality of portions of the stator winding may comprise circumferential segments of the stator winding, wherein at least one of the first and second indications may be developed by combining permeance contributions of each of the circumferential segments.
According to another aspect of the invention, the end-turn leakage flux approximation produced by the combining step comprises a parameter of a circuit model of the electric motor. Such a circuit model may be generated by computer to study the performance characteristics of new motor designs.
The method of the present invention may be embodied, for example, in a computer-based system for developing an end-turn leakage flux approximation for turns of coils of a stator winding of an electric motor having a stator with a predetermined number of stator slots within which the turns of the stator winding are distributed according to a predetermined distribution, said stator winding including at least two stator poles. One embodiment of such a system includes a processing unit coupled with a storage, a first set of instructions storable in the storage and executable by the processing unit for developing a first indication representing a pole-to-pole permeance based on an approximated leakage flux path linking two poles, a second set of instructions storable in the storage and executable by the processing unit for developing a second indication representing an individual pole permeance based on an approximated leakage flux path linking one pole, and a third set of instructions storable in the storage and executable by the processing unit for combining the first and second indications to produce an end-turn leakage flux approximation. In accordance with the method of the present invention, at least one of the first and second indications is developed in accordance with a discrete representation of the predetermined distribution of the turns of the stator winding.
The present invention alternatively may be embodied in a storage containing software for developing an end-turn leakage flux approximation for turns of coils of a stator winding of an electric motor having a stator with a predetermined number of stator slots within which the turns of the stator winding are distributed according to a predetermined distribution, said stator winding including at least two stator poles. Such a storage preferably includes means for developing a first indication representing a pole-to-pole permeance based on an approximated leakage flux path linking two poles, means for developing a second indication representing an individual pole permeance based on an approximated leakage flux path linking one pole, and means for combining the first and second indications to produce an end-turn leakage flux approximation, wherein at least one of the first and second indications is developed in accordance with a discrete representation of the predetermined distribution of the turns of the stator winding.
REFERENCES:
patent: 4442393 (1984-04-01), Abbondanti
patent: 5619435 (1997-04-01), Prakash et al.
General Electric Company
Horton Carl B.
Mullins Burton S.
Wasserbauer Damian G.
Welsh & Katz Ltd.
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