This study investigates the vibro-acoustic phenomena of an axial-flux permanent magnet machine, used as hoisting equipment for low and middle rise elevators. The primary aim of this work is to develop a method that can be used in the elevator industry, for understanding and influencing the factors affecting the acoustic behaviour of the machine. For this purpose, a multiphysics finite element model was built, coupling the electromagnetic, mechanical and acoustic environments created by the electrical machine. The first part of this thesis investigates the noise sources inside an elevator shaft. After a literature survey of the noise sources of electrical machines, the noise pressure in the elevator shaft was measured and evaluated based on the frequency content of the data. As a result, the study concentrated on the noise created by the active parts of the motor. The second part is focused on the governing equations for the electromagnetic and vibro-acoustic phenomena; solved by using the finite element method. The third part presents a model built for an axial-flux permanent-magnet machine, with the focus on the features and validation methods for the vibro-acoustic phenomena. The output of the model describes the acoustic response of the motor for different elevator speeds. The last part contains the most important findings of the work including the following: 1) the axial component of electromagnetic excitation has a dominant effect on noise emission, for the studied machine, in comparison with the tangential component; 2) the impact of mechanical resonances on the noise is substantial, even for very low electromagnetic excitations; 3) by reshaping the geometry of the machine, the eigenmode shapes can be altered and significant noise reduction can be achieved.
|Tila||Julkaistu - 2014|