Investigations On Vibration Characteristics Of Pm Motors Based On Phase Tuning

Permanent magnet (PM) motor featuring energy-saving, environmental protection and simple structure is in essence an electrical-mechanical system with symmetric structure and fluctuating inner forces. The fluctuating forces inevitably produce noise and vibration affecting the performance of the PM motor. Under the sponsorship of the National Natural Science Foundation Project (Grant No. 50705062), this thesis investigates the effect of the topology on the dynamic response of PM motors. The main content is as follows:1. Phase tuning analysis: Two possible excitations have been clarified. One is tooth frequency, and the other is pole frequency. The relationship between the slot/pole combinations and the unbalanced magnetic pull (UMP) & cogging torque (CT) induced by the two excitations has been clarified, and simple rules for the suppression of certain unexpected vibration are also proposed. The relationship between two frequencies and the influence of it on vibration characteristics of PM motors have been investigated. A unified explanation on the two frequencies is presented.2. Finite element simulation: The tangential and radial magnet pulls acting on the PM motor have been calculated by ANSYS. And the UMP & CT of PM motors are obtained by using the superposition method with an aim to verify the above-mentioned relationships. The simulation results are well consistent with the theoretical analysis.3. PM symmetry Analysis: The influence of the PM shifting on the UMP & CT is investigated by using the Fourier series. The analytical expression of the PM shifting is obtained, and thus a new method for the shifting angles selection to reduce vibration has been achieved. The vibration reduction effect of this method is verified by the finite element results.The studies mentioned above provide a foundation to the low noise and vibration design of the PM motor. Although the PM motor is used as an example to analyze the relationship between the topology and the dynamic characteristics, the superposition method used in this thesis can apply for other symmetric system with fluctuating internal forces. In fact, this thesis provides a general guidance to the analysis and design of the symmetric systems.