Method for detection of interlaminar sheet short circuits in the stator sheet core of electromachines
First Claim
1. A method for detection of interlaminar laminate shorts in a laminated stator core of electrical machines, the method comprising;
- subjecting the laminated stator core to an externally applied field current or field voltage;
measuring, with a sensor coil, a short-circuit magnetic field induced by short-circuit currents the sensor coil being arranged in a gap in a machine and probes the gap, wherein the field current and field voltage have a non-sinusoidal shaped waveform, and the non-sinusoidal shaped waveform of the field current or field voltage is a periodic waveform with significant higher harmonics; and
evaluating both a fundamental frequency and a harmonic of a signal produced by the sensor coil, subjecting the signal recorded in the sensor coil to spectral analysis with assistance of a Fourier transformation for identification of the interlaminar laminate shorts, and using a phase spectrum of various harmonics for identification of the interlaminar laminate shorts on a basis of phase angles in individual harmonics of the various harmonics.
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Accused Products
Abstract
A method and an apparatus are described for detection of interlaminar laminate shorts in the laminated stator core of electrical machines, in which the laminated stator core (4) is subjected to an externally applied field current (2) or field voltage (V), and the short-circuit magnetic field (Bshort) induced by short-circuit currents (5) is measured with the assistance of a sensor coil (S1) which is arranged in the gap in the machine and probes this gap. Improved identification of laminate shorts, in particular even of small laminate shorts with small short-circuit currents, is possible in that a field current (2) and a field voltage (V) are applied which have a waveform which differs significantly from a sinusoidal shape, in particular with a periodic character, and have significant harmonic components in the high frequency range. By way of example, a waveform in the form of a square-wave curve is proposed.
30 Citations
21 Claims
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1. A method for detection of interlaminar laminate shorts in a laminated stator core of electrical machines, the method comprising;
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subjecting the laminated stator core to an externally applied field current or field voltage; measuring, with a sensor coil, a short-circuit magnetic field induced by short-circuit currents the sensor coil being arranged in a gap in a machine and probes the gap, wherein the field current and field voltage have a non-sinusoidal shaped waveform, and the non-sinusoidal shaped waveform of the field current or field voltage is a periodic waveform with significant higher harmonics; and evaluating both a fundamental frequency and a harmonic of a signal produced by the sensor coil, subjecting the signal recorded in the sensor coil to spectral analysis with assistance of a Fourier transformation for identification of the interlaminar laminate shorts, and using a phase spectrum of various harmonics for identification of the interlaminar laminate shorts on a basis of phase angles in individual harmonics of the various harmonics. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for carrying out a method for detection of interlaminar laminate shorts in a laminated stator core of electrical machines, in which the laminated stator core is subjected to an externally applied field current or field voltage, and a short-circuit magnetic field induced by short-circuit currents is measured by a sensor coil which is arranged in a gap in a machine and probes the gap, wherein the field current and field voltage have a non-sinusoidal shaped waveform, the apparatus comprising;
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a sensor coil is arranged in the laminated stator core; a field apparatus for production of a field voltage or a field current also arranged in the laminated stator core; and a frequency generator provided in order to operate the field apparatus, and is configured to operate the field apparatus with a field current or a field voltage with a non-sinusoidal shaped waveform, and the non-sinusoidal shaped waveform of the field current or field voltage is a periodic waveform with significant higher harmonics, wherein both a fundamental frequency and a harmonic of a signal produced by the sensor coil are evaluated, the signal recorded in the sensor coil is subjected to spectral analysis with assistance of a Fourier transformation for identification of the interlaminar laminate shorts, and a phase spectrum of various harmonics is used for identification of the interlaminar laminate shorts on a basis of phase angles in individual harmonics of the various harmonics. - View Dependent Claims (19, 20, 21)
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Specification