Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1994-11-21
1996-10-15
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
318607, 318632, G05D 23275, G05D 102, H02K 709
Patent
active
055657222
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a magnetic bearing control system for the stable support of an object mounted without contact in the magnetic field of a stator, whereby magnetizable components in the stator cooperate with magnetizable components of the object. At least two electrical coils connected in series serve as the bearing element, and this pair of coils operates simultaneously as a position sensor and as an electromagnetic positioning unit, whereby the magnetic field of the stator operating on the object and designated as biasing runs parallel to the direction of magnetizing of the coils.
Magnetic bearings for support of objects without contact are described, for example, in G. Schweitzer (Editor), "Magnetic Bearings", Proceedings of the First Int. Symp. ETH-Zurich, Switzerland, 1988. For rotor shafts, however, magnetic bearings are also known for measurement objects suspended in the magnetic field from DE Patent 2,444,099 and DE Patent 3,808,331. The magnetic bearings have permanent magnets, in the magnetic field of which, the object to be supported, which on its side has magnetic or magnetizable components, is introduced. Electrical control systems, the output signals of which vary the magnetic fields produced by the electrical coils, serve for stabilizing the mounting. The prevailing magnetic field intensity corresponding to the output signal of a position sensor between the magnetizable magnetic bearing components is influenced by the control system, and this sensor measures the existing distance between the object supported without contact and the magnetic stator.
An electromagnetic bearing element for two degrees of freedom with respect to the motion of the supported rotor with pairs of coils connected in series is known from DE OS 2,537,597, and these pairs of coils serve as a position sensor as well as an electrical positioning unit. In this arrangement, all individual coils are placed on a common core, and are thus magnetically coupled. With such a bearing element, there are considerable electromagnetic influences of the sensor currents due to the bearing fluxes, and vice versa, and this occurs in both degrees of freedom. These undesired influences can be reduced only by considerable expenditure with respect to circuits, such as multiple arrangements of coils for each degree of freedom, by dividing the coils, or by taps and a corresponding electrical circuitry.
A high-frequency measurement bridge circuit is described in a patent application P 42 10 741.5 (PT 1.1126), which has not been prepublished, for reduction of magnetic bearing components, in which electrical coils serve in the same way as in the case of DE OS 2,537,597 for control of the central position of the object that is supported without contact simultaneously as a position sensor and as an electromagnetic positioning component for a permanent magnetic bearing.
The object of the invention is to create a control system for a magmatic bearing with a small number of control components, which has a high operating reliability with a simple and cost-favorable configuration.
This object is attained for a magnetic bearing control system of the type named initially according to the invention, that the pair of coils are connected in series electrically, but the coils are arranged magnetically in opposite positions, and with both of their outer ends combined with an output of an amplifier, whereby one of the two amplifiers supplies the inverted output signal of the other amplifier. In the known way, a high-frequency signal of an oscillator, particularly a sinusoidal high-frequency signal is applied to the input of the amplifier, and this signal feeds into the pair of coils via the two amplifiers and is read off between the two coils via a high-pass filter by a phase-sensitive rectifier (synchronous rectifier), which is timed with the high-frequency signal of the oscillator. The phase-sensitive rectifier is turned on at the electrical "central point" between the two coils, whereby the two inverted high-frequency signals fed into the coils at this p
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patent: 4585282 (1986-04-01), Bosley
patent: 4697128 (1987-09-01), Matsushita et al.
patent: 4841212 (1989-06-01), Matsushita et al.
patent: 5053662 (1991-10-01), Richter
patent: 5126610 (1992-06-01), Fremerey
Magnetic Bearings, G. Schweitaer (editor), Proceedings of the First Int'L Symposium ETH Zurich, Switz., Jun. 6-8, 1988.
Lindenau Bernd
Rubner Wolfgang
Forschungszentrum Julich GmbH
Stephan Steven L.
Wallace, Jr. Michael
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