Title :
Detection of mechanical imbalances without frequency analysis
Author :
Kral, C. ; Habetler, T.G. ; Harley, R.G.
Author_Institution :
Sch. of Electr. & Comput. Eng., Georgia Inst. of Technol., Atlanta, GA, USA
Abstract :
Mechanical rotor imbalances and rotor eccentricities are reflected in electric, electromagnetic and mechanical quantities. Therefore, many surveillance schemes determine the Fourier spectrum of a single line current in order to monitor the motor condition. Mechanical imbalances give rise to two first-order current harmonics. Due to the interaction of the currents and voltages, both these current harmonics are also reflected by a single harmonic component in the frequency spectrum of the electric power. This single component is easier to assess than both the current harmonics. The technique proposed in this contribution evaluates this imbalance-specific modulation of the electric power. The proposed approach is not a frequency domain method, though. The imbalance specific oscillation of the electric power is extracted by a band-pass filter. Then, the averaged pattern of this component is determined by means of an angular data clustering technique. In that way the oscillation of the electric power in the time domain becomes mapped into a discrete waveform in an angular domain. The fundamental of these discrete data serves as an imbalance indicator of the proposed scheme. This technique, therefore, overcomes small load and slip fluctuations. Measured results of a mechanically unbalanced machine and a case of combined static and dynamic eccentricity are presented.
Keywords :
band-pass filters; fault diagnosis; induction motors; rotors; statistical analysis; 10 kW; angular data clustering technique; angular domain; averaged pattern; band-pass filter; combined static and dynamic eccentricity; discrete data; discrete waveform; electric power; first-order current harmonics; frequency spectrum; harmonic component; imbalance specific oscillation; imbalance-specific modulation; induction motors; mechanical rotor imbalances detection; mechanically unbalanced machine; rotor eccentricities; time domain; Band pass filters; Condition monitoring; Data mining; Fluctuations; Frequency domain analysis; Power harmonic filters; Power system harmonics; Rotors; Surveillance; Voltage;
Conference_Titel :
Diagnostics for Electric Machines, Power Electronics and Drives, 2003. SDEMPED 2003. 4th IEEE International Symposium on
Print_ISBN :
0-7803-7838-5
DOI :
10.1109/DEMPED.2003.1234593