The Simulation Analysis On Alternator’s Electromagnetic Noise

While cars are becoming more and more popular in China, people are paying much more attention on the vehicle comfort. Alternator as one essential part of a car, the noise criteria is becoming much more strict.According to the problem, stator exposed vehicle alternator’s noise excess in low speed (below5000r/min), which is caused by electromagnetic noise, research about electromagnetic resonance was done through comparisons between simulation and test results. The study is divided into three parts, structural modal, electromagnetic vibration response and electromagnetic acoustic radiation.Firstly, the finite element model of the main generator parts and the whole were established in Hyper Mesh. Then the Block Lanczos method is used in ANSYS to calculate the free-state parts’modal in order to calibrate the material parameters. Modal calculation of the whole is calculated in the restraint state. Generator modal experiments were done through mobile hammer hammering method on the platform of LMS Test. Lab. The modal calculation results and modal experimental results are consistent. Also the study of how the structure modes change with the improvement of generator’s material stiffness. Taking various factors into consideration, it was found that increasing the stiffness of the front and rear cover is the way to improve the motor’s natural frequency, which was also proved by experiments.Next, research about the characteristics of electromagnetic force and its loading methods was done. After comparing results of different loading methods, a reasonable simplified method was gotten. Using the simplified method, generator’electromagnetic vibration response was calculated. The generator vibration tests were done and that prove the rationality of electromagnetic vibration response.Lastly, electromagnetic vibration response results were imported to LMS Virtual. Lab and transient boundary element method is used to calculate electromagnetic acoustic radiation and the sound radiation results were achieved. To verify the calculation results, noise tests were done in specifically designed lab. The electromagnetic noise in case of stator’s deformation and bias was also calculated.Stator exposed vehicle alternator’s electromagnetic noise was researched through simulations and experiments. The simulation analysis process laid a foundation for the deep study of electromagnetic noise and has some reference value.