D Verdyck

Electro-mechanical analysis of the audible noise of an inverter-fed squirrel-cage induction motor

The audible noise emitted by a three-phase squirrel-cage induction motor fed by a frequency inverter is determined by the electromagnetic and mechanical behavior of the components of the drive. A computerized analysis method is described which uses theoretical as well as experimental data for predicting the audible noise spectrum components. Starting from the inverter voltage and the motor data, the electromagnetic forces are predicted and analyzed. The mechanical natural frequencies are considered, either in a theoretical (finite-element calculation) or in an experimental (modal analysis) methodology, in order to predict the vibrational behavior of the machine.<<ETX>>

An acoustic model for a permanent magnet machine: modal shapes and magnetic forces

A modal analysis concept for calculating the vibrational level of an electrical machine stator is presented. Using this concept, the designer is freed from calculating real magnet forces, which is normally difficult and inaccurate. Only flux linkages have to be calculated which can be easily done using finite element methods and the vector potential as the unknown function. Furthermore, the energy method also deals with any random or tangential movement of the stator surface. The main disadvantage is the need to know the mode shapes accurately. These can only be measured with great effort in the low-frequency region (up to 1 kHz). In the higher frequency regions, hundreds of modes exist, although, at this point, other approximations can be made.<<ETX>>

An approach to modelling of magnetically excited forces in electrical machines

A distinction is made between the vibrations produced by the fundamental current supplying the machine and the much smaller higher harmonic currents, with frequencies ranging into the kilocycles range. The small harmonic currents are emphasized. An appropriate mathematical modeling technique is presented. A mechanical model is selected based on modal analysis techniques. A method is developed for finding the driving force for each mode shape. This is illustrated with measurements on a permanent magnet machine. Experimental verifications of the model show the importance of a correct knowledge of eigenfrequencies and damping coefficients. >

Magnetic field analysis in squirrel cage induction motors

A method for analyzing the field in a squirrel-cage induction motor is discussed, starting from a classical design scheme but using the finite element technique. The approach considered allows the calculation of the flux density distribution in an induction motor at different operating points. A magnetostatic approach is used to model the no-load situation; for the locked rotor situation, a time harmonic solution is used. This leads to the calculation of induced currents, accounting for the real saturation. The parameters deduced from these calculations are influenced by the local saturation, and overall correction factors may be avoided. This approach may be used for all three-phase systems, having a flux pattern that remains virtually the same as a function of time. It is shown that a combination of a correct flux distribution calculation method with appropriate input and output routines may lead to a design procedure which can be used by industrial manufacturers. >

A vibrational model using modal shapes and magnetic forces: experimental results for a permanent magnet machine

ContentsThe frequency inverter current spectrum generates a complex magnetic field in the airgap producing attracting forces having a wide spectrum and leads to audible noise. A mathematical model is presented, predicting vibrations of a permanent magnet machine, based on the modal analysis technique including mechanical damping. Modal forces produced by the magnetic field, are related to the supply currents using a finite element calculation. Experimental results are presented.ÜbersichtDas Stromspektrum eines Frequenzumrichters generiert ein komplexes magnetisches Feld im Luftspalt, welches Anziehungskräfte mit einem breiten Frequenzgang hervorruft, die wiederum zu Geräuschen führen. Ein mathematisches Modell wird vorgestellt, welches es ermöglicht, die Schwingungen einer permanent erregten Maschine vorauszusagen. Es basiert auf der Modalen Analyse und enthält die mechanische Dämpfung. Vom Magnetfeld hervorgerufene modale Kräfte werden mit den eingespeisten Strömen mittels der Finite-Elemente-Methode in Verbindung gebracht. Experimentelle Ergebnisse werden dargestellt.

A Modern Approach to Electrical Machine Design

SUMMARY Electrical machine design is a difficult and multidisciplinary task which can now be made easier by the use of computers. This paper discusses how computers can aid the achievement of a better product as well as coping with the kinds of demands now placed on the product and product development.

Computer Aided Design of Nd-Fe-B Permanent Magnet Motors

This paper deals with the various aspects encountered in the design of permanent magnet motors using Nd-Fe-B.