Simulation Analysis Of A Vehicle Generator’s Electromagnetic Noise Under Mechanical And Electrical Faults

Noise is generated when a generator runs, including mechanical noise, aerodynamic noise and electromagnetic noise. The air-gap between stator and rotor magnetic field in vehicle generator’s produces a series of electromagnetic force waves, which results in resonating and radiating electromagnetic noise. In normal operation, the first-order tooth harmonic force is the main reason for electromagnetic noise. In faulty operation, the electromagnetic noise changes as fundamental wave force and tooth harmonic force are changed. Based on a type of vehicle generator, the acoustic characteristic is studied on when it’s on mechanical and electrical faulty conditions. The contents of this paper include the followings: analyzing of electromagnetic property, analyzing of structural dynamic response and analyzing of the acoustic radiation.These faults includes the followings: rotor static eccentricity, stator winding short circuit fault and stator winding phase fault. In this paper, the methods of fault setting are presented, which can be set as a reference for the same category of generator and other kinds of faults.Firstly, according to the relevant parameters of the alternator, a finite element electromagnetic model is built up by using Ansoft. Generator faulty state and operation conditions(i.e. no load and load) are simulated by using the relative coordinate system and the external circuit model. The electromagnetic property of the generator is analyzed by electric field, magnetic flux density and radial electromagnetic force. The amplitude, frequency and initial phase of the first order tooth harmonic forces(i.e. 36 th order radial electromagnetic force) on stator tooth surface are extracted. The electromagnetic properties of the generator under different eccentric weights are analyzed, and the change tendency is obtained.Secondly, a finite element mechanical model is built up by using Workbench. The intrinsic modes of complete machine and stator are analyzed. Harmonic response results are calculated after exerting the 36 th order radial electromagnetic forces, including vibration displacement frequency response results and vibration clouds. Harmonic response results under different faulty conditions are compared and analyzed.Finally, importing the harmonic response vibration displacement results to acoustic indirect boundary element module. Receiving the noise level curves and SPL cloud of the vehicle alternator under different faulty types and different operating conditions. The results show that the acoustic radiation characteristics of the electromagnetic noise are different from the faulty types and operating conditions In this paper, the electromagnetic noise of claw pole generator with different kinds of faults is simulated and analyzed by using the finite element method, and the electromagnetic noise’ acoustic radiation characteristics are obtained under different faulty types and different operating conditions. The methods being used in the paper are significant in the phase of product failure analysis. These also provide a reference method for new design and research to improve generator electromagnetic noise problem.