WO2008106910A1 - Machine électrique et procédé pour mesurer le potentiel appliqué à un élément mobile d'une machine électrique - Google Patents

Machine électrique et procédé pour mesurer le potentiel appliqué à un élément mobile d'une machine électrique Download PDF

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Publication number
WO2008106910A1
WO2008106910A1 PCT/DE2007/000425 DE2007000425W WO2008106910A1 WO 2008106910 A1 WO2008106910 A1 WO 2008106910A1 DE 2007000425 W DE2007000425 W DE 2007000425W WO 2008106910 A1 WO2008106910 A1 WO 2008106910A1
Authority
WO
WIPO (PCT)
Prior art keywords
movable
movable element
electric machine
potential
measuring
Prior art date
Application number
PCT/DE2007/000425
Other languages
German (de)
English (en)
Inventor
Jörg HASSEL
Hans-Richard Kretschmer
Arno Steckenborn
Oliver Theile
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Priority to PCT/DE2007/000425 priority Critical patent/WO2008106910A1/fr
Priority to DE112007003497T priority patent/DE112007003497A5/de
Publication of WO2008106910A1 publication Critical patent/WO2008106910A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines
    • G01R31/343—Testing dynamo-electric machines in operation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
    • G01R29/12—Measuring electrostatic fields or voltage-potential

Definitions

  • the invention relates to an electrical machine and to a method for measuring the potential applied to a movable element of an electrical machine.
  • a capacitive element for measuring a static potential, at least part of which is moved in such a way that the capacitance of the capacitive element changes and a Maxwellian displacement current flows.
  • the potential can then be derived from the current intensity of the Maxwell's displacement current.
  • This principle is used for example in the so-called field mill (see, for example, US Pat. No. 5,315,232) and in the measuring device known from WO 2005/121819 A1.
  • the potential to be measured is applied to an immovable element.
  • preventive maintenance As part of the so-called preventive maintenance (known in English as “preventive maintenance”) should take place at an aging of the machine regularly replacement of components of the electric machine or the entire electric machine to avoid a surprising defect in the electrical machine. It would be desirable to be able to detect or even avoid flashovers in a timely manner, since it is reasonable to do so by measuring the potential applied to the moving element of the electric machine During the operation of the electrical machine, no method for measuring the potential on such a movable element of an electrical machine is known in the prior art.
  • the electric machine comprises a predetermined manner movable, electrically conductive element and a stationary, electrically conductive element which is coupled to the movable member such that the immovable member and the (electrically conductive) surface of the movable member each side of a form capacitive element.
  • the surface of the movable element is designed such that the capacitance of the capacitive element changes as the movable element moves in the predetermined manner.
  • the electric machine has means for measuring the amplitude of the current flowing to and away from the immovable element.
  • the invention is based on the recognition that, with variable capacitance between immovable element and the surface of the movable element, a Maxwellian displacement current flows whose current intensity is proportional to the electric potential difference given between the movable element and the immovable element. It is only necessary to know or determine the proportionality factor. Since the potential measurement on the movable element does not have to be highly accurate, but merely has to provide a clue as to whether arcing can take place, it is sufficient if the proportionality factor is known on the order of magnitude.
  • the movable member may be a rotatably movable cylindrical member, and then a portion of the cylinder surface of the movable member provides a part of the capacitive element.
  • the movable element may also be a translationally movable plate-shaped component, and a portion of a planar surface of the movable element then provides a part of the capacitive element.
  • Separate evaluation means are preferably provided in the electrical machine which receive measurement signals from the means for measuring the current intensity and are designed to derive a value for the potential applied to the movable element from the measurement signals on the basis of a mathematical or an empirically determined relationship. As already mentioned, this value need not be highly accurate, but may be subject to an error such that the evaluation means indicate an interval for the value of the electric potential.
  • the evaluation is preferably coupled to a measurement of the respective rotational position. This can be done, for example, by providing optical sensors for sensing the movement of the movable element, which is possible when the surface of the movable element is designed so that the capacitance of the capacitive element changes as it moves their appearance changes so that the phase is derivable.
  • the optical sensors can then send measurement signals to the evaluation means, and the evaluation means only have to incorporate the measurement signals of the optical sensors in the derivation of the electrical potential from the measurements of the means for measuring the amplitude of the current amplitude.
  • the optical signals can be used to specify clock rates for the interrogation of the current amplitude signals.
  • the capacitance for a plate capacitor is a function of the area of the plates, the spacing of the plates, and the dielectric constant of the inter-plate dielectric, which may be air. Accordingly, the formation of the surface of the movable member for For purposes of changing the capacitance of the capacitive element in the movement of the movable member so that the electrically conductive surface of the movable member is structured so that when moving the movable member, the distance between immovable member and the surface of the movable member changes. It is also possible to apply electrically non-conductive material to a part of the electrically conductive surface of the movable element, and both measures can be taken simultaneously. (A change in the area of the facing sides of the capacitive element is difficult to constructively realize.)
  • the immovable element is preferably plate-shaped, wherein the plate shape may be flat or curved.
  • the curvature radius may be selected such that the center of the circle defining the curvature radius coincides with the center point of the cylindrical shape of the movable component.
  • the immovable element is preferably mechanically connected to other immovable components of the electrical machine, ie with the stator or at least the housing in which the stator is arranged.
  • the electrical connection is not immediate, but z. B. via a rectifier or z. B. via an analog-to-digital converter with subsequent digital evaluation, then continue on the downstream means for measuring the current amplitude and possibly the evaluation.
  • the method according to the invention for measuring the potential applied to a movable element of an electrical machine comprises the steps:
  • the evaluation is preferably coupled to the actual movement of the movable element.
  • the moveable element moves in rotation
  • its rotation speed is measured and included in deriving the potential from the measured values of the current amplitude amplitude.
  • the translation speed of the movable element is measured and included in deriving the potential from the measured values of the current amplitude.
  • FIG. 1 shows in cross-section the capacity-forming parts of the electric machine according to a first embodiment of the invention
  • FIG 2 shows in perspective the complete arrangement of the electric machine in this embodiment
  • 3 shows in cross-section the capacity-forming parts of the electric machine according to a second embodiment of the invention
  • 4 shows in cross section the capacitance-forming parts of the electric machine according to a third embodiment of the invention
  • FIG 5 illustrates in cross section to the second embodiment of the invention according to FIG 3, an optical scanning.
  • a shaft 10 shown in FIG. 1 in cross-section and in FIG. 2 in a perspective illustration is a movable element
  • a variable capacitance is to be used so that a Maxwellian displacement current proportional to the applied voltage U flows.
  • a capacitor plate 18 is provided as a stationary element. 2 and dashed line in FIG. 1, or it may be curved, compare solid line in FIG. 1.
  • the plate 18 is provided with a measuring transducer 20 (eg current-voltage converter). connected.
  • the transducer 20 is connected at its output to means 22 for measuring the level of the signals emanating from the transducer 20, and the means 22 for measuring this signal level are followed by evaluation means 24 which receive and evaluate the measured values.
  • FIG. 1 shows an embodiment in which approximately a plate capacitor is formed between the shaft 10 and the plate 18, wherein the distance between the plates changes periodically.
  • 10 teeth 26 are formed on the shaft 10 via an axial portion of the shaft, which are also electrically conductive.
  • the shaft 10 can be suitably milled from a metal part. If a tooth 26 passes by the plate 18, the distance between the two sides of the capacitive element is small. If a gap 28 between two teeth 26 arrives the plate 18 over, this distance is greater.
  • a Maxwell shear displacement current which is proportional to the voltage U. This Maxwell's displacement current is rectified by the transducer 20 and its amplitude is measured by the means 22 for measuring the amplitude.
  • the measured values are supplied to the evaluation means 24.
  • the evaluation means 24 is either a mathematical relationship, for example according to equation (3) with numerical values for the constant factors, stored, or an empirical relationship with table values.
  • the evaluation means 24 can then react on the voltage U.
  • the voltage U should be measured in order to be able to foresee damaging flashovers in good time for the electric machine 12.
  • Either the numerical value of the voltage U is displayed or indicated on a display 30 that the voltage U has exceeded a limit from which the electrical machine 12 could suffer damage due to currents and flashovers laying down on the voltage U, or it is sent to a warning lamp 32 a current signal is output so that it indicates when the voltage U has exceeded a predetermined limit.
  • the interspaces between the teeth 26 are filled with a dielectric 34.
  • the distance d changes, but not so that ⁇ is constant, but over a part of the distance the dielectric constant ⁇ of the dielectric 34 is to be used.
  • the Maxwellian displacement flow is lower, because an increase of ⁇ counteracts an increase of the distance d, compare the plate capacitor formula (3).
  • the electrically conductive material of the shaft is continuously circular in cross-section, and over an axial portion of a dielectric 36 is applied.
  • the dielectric 36 can be provided, for example, by simple adhesive tape ("tape"). In this case, only the dielectric is changed upon rotation of the shaft 10 ", ie ⁇ changes, while the distance d between the electrically conductive ones changes Components is defined, remains constant.
  • All three embodiments are such that the surface also changes optically upon rotation of the respective shaft.
  • a suitable optical scan 38 eg LED light barrier
  • the surface can be permanently scanned.
  • the LED light barrier 38 thus determines the rhythm of the changes on the surface with the rotation of the shaft and the LED light barrier 38 is coupled to the evaluation means 24.
  • the latter can set the measurement signals output by the current amplitude amplitude measuring means 22 in relation to the measurement signals of the LED light barrier 38, so that a phase relationship is determined.
  • the measurement signals from the measuring means 22 can thus be interrogated synchronously. As a result, the influence of interference signals, which naturally can occur with the size of the electric machine 12, is suppressed.
  • the principles of the invention can also be applied to an electric machine with a translationally movable element (linear motor).
  • the translationally movable member may be plate-shaped, and the surface of this plate may be made uneven, corresponding to the teeth 26 of the shaft 10 or 10 '.
  • the dielectric material can also be applied to the plate.
  • strips of dielectric adhesive tape of the type of strips 36 may be applied to shaft 10 'at fixed intervals.

Abstract

Le potentiel appliqué à un élément mobile (10) d'une machine électrique est mesuré en formant avec un élément immobile supplémentaire (18) une capacitance par rapport à l'élément mobile. La surface de l'élément mobile est configurée de telle sorte que la capacitance varie lors d'un déplacement de l'élément mobile (10) de sa manière prédéfinie. Cette variation de la capacitance engendre la circulation d'un courant de déplacement de Maxwell qui est proportionnel au potentiel à mesurer.
PCT/DE2007/000425 2007-03-08 2007-03-08 Machine électrique et procédé pour mesurer le potentiel appliqué à un élément mobile d'une machine électrique WO2008106910A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/DE2007/000425 WO2008106910A1 (fr) 2007-03-08 2007-03-08 Machine électrique et procédé pour mesurer le potentiel appliqué à un élément mobile d'une machine électrique
DE112007003497T DE112007003497A5 (de) 2007-03-08 2007-03-08 Elektrische Maschine und Verfahren zum Messen des an einem beweglichen Element einer elektrischen Maschine anliegenden Potentials

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DE2007/000425 WO2008106910A1 (fr) 2007-03-08 2007-03-08 Machine électrique et procédé pour mesurer le potentiel appliqué à un élément mobile d'une machine électrique

Publications (1)

Publication Number Publication Date
WO2008106910A1 true WO2008106910A1 (fr) 2008-09-12

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE2007/000425 WO2008106910A1 (fr) 2007-03-08 2007-03-08 Machine électrique et procédé pour mesurer le potentiel appliqué à un élément mobile d'une machine électrique

Country Status (2)

Country Link
DE (1) DE112007003497A5 (fr)
WO (1) WO2008106910A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4963829A (en) * 1988-03-21 1990-10-16 Wereb John A Shaft rotation analyzer using variable capacitance transducer maintained at a constant voltage
US5315232A (en) * 1991-01-03 1994-05-24 Stewart Michael F Electric field measuring system
US5448337A (en) * 1994-06-23 1995-09-05 Williams; Bruce T. Method and apparatus for determining the charge or voltage distribution of an electrophotographic surface
WO2006134068A1 (fr) * 2005-06-15 2006-12-21 Siemens Aktiengesellschaft Dispositif et procede de controle du courant de palier d'un moteur electrique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4963829A (en) * 1988-03-21 1990-10-16 Wereb John A Shaft rotation analyzer using variable capacitance transducer maintained at a constant voltage
US5315232A (en) * 1991-01-03 1994-05-24 Stewart Michael F Electric field measuring system
US5448337A (en) * 1994-06-23 1995-09-05 Williams; Bruce T. Method and apparatus for determining the charge or voltage distribution of an electrophotographic surface
WO2006134068A1 (fr) * 2005-06-15 2006-12-21 Siemens Aktiengesellschaft Dispositif et procede de controle du courant de palier d'un moteur electrique

Also Published As

Publication number Publication date
DE112007003497A5 (de) 2010-02-11

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