Research On Electromagnetic Vibration Problems Of Inverted-Fed Induction Machine

Frequency control of induction motors'speed has greatly broaden the application of induction motor,but also greatly increase the difficulty of its noise and vibration control technology.It has become the technological bottlenecks of inverted-fed induction machine, especially in those applications which requires low noise and vibration.Electromagnetic excitation force, air flow and mechanical friction are the three main macroeconomic factors of motors'vibration and noise. The latter two are the main factors causing noise and vibration intensified with the increase of the motor speed Electromagnetic excitation force is affected by many factors, such as motor alveolar structure, ferromagnetic materials, rotor concentricity, etc. especially for inverted-fed induction machine, the stator current harmonics contains a lot of high order harmonic harmonics,which has become technical difficulty of noise and vibration analysis.The subject comes from the defense industry Bureau of Science and Technology Project.This paper makes deep research of the inverted-fed induction machines' electromagnetic vibration from three aspects. First, confirm the relationship between the voltage source, the magnetic flux density, magnetic excitation force and vibration with the analytical method, especially for the impact of the motor vibration,caused by high order harmonic in inverted-fed. Second, make transient magnetic analysis of the ends of the induction machine and the body's magnetic field in inverted-fed conditions with numerical calculation method. It can discuss the harmonic frequency components of electromagnetic excitation force and the vibration impact of electromagnetic excitation force when the force is applied on the stator core.The third is to verify the feasibility of analytical and numerical calculations using the experimental method.This paper mainly includes the following sections:In the first part, it has carried on a simple introduction of the electromagnetic force's calculation method, which mainly including Lorentz force method an Maxwell stress tensor method and virtual displacement method.Then this part has also studied radial electromagnetic force which is the main vibration source of electromagnetic noise according to the classical maxwell stress tensor method. Finally, the calculation method of radial electromagnetic force is deduced respectively under the condition of the sine power supply and converter's power supply. The second part is the research of the ends of magnetic field through numerical calculation method in inverted-fed condition. For inverted-fed, traditional calculation are often used the method of equivalent, namely through the experiment to obtain the current in the stator winding and loads it into the end windings then make transient calculation. This method can avoid considering the three-dimensional vortex field problem caused by the rotor rotating, but in the presence of measurement error is inevitable. Therefore, this chapter uses a three-dimensional field circuit coupled stepping finite element method, considering the rotor rotates, electromagnetic field equations,circuit equations and the equation of rotor motion to solve transient magnetic field of winding ends.Magnetic field measurement results were compared with the calculation results to infer the spectral characteristics of the winding ends'magnetic field.In third part, electromagnetic excitation force of inverter-fed induction machine body's calculated problem is solved by two-dimensional field processing circuit coupled FEM. It has calculated inverter-fed induction machine body's radial and tangential electromagnetic force and focused on radial electromagnetic force which has greater impact on vibration. Firstly, it make a analysis of frequency characteristics about the stator phase current,the stator voltage, radial electromagnetic force similarities and differences in both sinusoidal-fed and inverter-fed conditions. Secondly, it verifies the radial slot frequency component in Radial electromagnetic force spectrum. Then, make a discuss about the effects of different loads on the stator voltage, the stator phase current,the radial electromagnetic force. Finally, It analyzes the impact of the switching frequency on the radial electromagnetic force.Section IV presents a transient magnetic-structural treatment of transient dynamics indirect coupling method to solve transient dynamic response problems caused by inverter-fed, taking into account changes of radial electromagnetic force in time and space (neither static, and non-sinusoidal force) and make an analysis of the response of the stator structure of the radial electromagnetic force, solving the motor structure's displacement, velocity, acceleration, and concerned acceleration spectral characteristics, etc. It provides an important theoretical guidance for the structural design of the motor vibration.