Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1996-06-11
1998-01-13
Ip, Paul
Electricity: motive power systems
Induction motor systems
Primary circuit control
318811, 318805, 318808, H02P 540, F16C 3906
Patent
active
057083460
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to the field of drive and regulation technology.
2. Description of the Prior Art
The preconditions under which one-sided magnetic trains arise in electrical machines were already being investigated at the start of this century. There are for example described in the three-volume fundamental work by H. Sequenz "The Windings of Electrical Machines", Springer-Verlag Wien, 1950 and also in the textbook by Th. Bodefeld and H. Sequenz, sixth edition, Springer-Verlag Wien, 1962. In accordance with Sequenz, one-sided magnetic tension forces only then arise when the resulting magnetic flux polygon is centrally asymmetric and is first closed after running around the entire armature circumference. The radial Maxwell forces distributed around the entire circumference do not cancel when the vector sum is taken so that a tensile force results. Two cases are described in the fundamental work by H. Sequenz which bring about a central asymmetry of the magnetic flux polygon: pair differences relative to one another or relative to the fundamental wave are equal to one, whose pole pair difference is equal to one.
For a long time one-sided magnetic trains were exclusively considered by electrical engineers as undesired disturbing forces and were counteracted by suitable measures. P. K. Hermann attempted for the first time to exploit one-sided magnetic trains acting in an electrical machine. In the German patent applications tensile forces. He proposes a control method in which two stator windings of an induction machine with a pole pair number difference of one is fed with three phase currents of the same frequency, with the feed current for the one winding, which is referred to in the following as the control winding, being derived by amplitude modulation from the feed current for the other winding, referred to in the following as the drive winding. The phase position between the currents of the two windings, referred to in the following as the control current and drive current, is matched by means of a phase adjusting device.
A disadvantage of this control lies in the fact that the direction and the magnitude of the magnetic tensile force controlled via the control current, referred to in the following as the Maxwell transverse force, depends on the load state and on the speed of rotation of the machine. Furthermore, with the described control, the transverse Lorentz forces which likewise occur with the combination of two winding systems with a pole pair number difference of one are not taken into account. These can therefore make themselves felt as disturbing forces.
A proposal to exploit these Lorentz transverse forces which occur with the combination of two winding systems with a pole pair number difference of one originates from J. Bichsel. In his dissertation "Contributions to the bearingless electric motor", ETH Zurich, 1990 and in the Swiss patent applications Lorentz transverse forces. He also describes a control method based on the principle of flux orientation for a synchronous machine, which makes it possible to adjust the magnitude and direction of a Lorentz transverse force independently of the operating point of the machine. A disadvantage of the control process lies in the fact that it does not take account of the Maxwell transverse forces. Moreover, the method cannot be transferred to an induction machine, since there no exploitable Lorentz transverse force can be generated.
For the realization of the control method of the invention, the magnitude of the drive flux, the angle of the drive flux and the torque-forming stator drive current in the induction machine need to be known. Methods for the determination of these parameters are described extensively in the literature under the heading "Field Orientated Regulation or Control of the Synchronous Machine and the Asynchronous Machine". The fundamental principles of the field orientated control go back to F. Blaschke (The Method of Field Orientation for the Regulation of the Asynchronous Mach
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Ip Paul
Lust Antriebstechnik GmbH
Sulzer Electronics AG
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