Study On Electromagnetic Characteristics Of Brushless Claw Pole Generator For Vehicle

With the gradual increase of electric load inside the automobile,the demand for the capacity level of the automobile generator is also increasing.The electric excitation claw pole generator is widely used in the field of automobile power generation due to its advantages of high mechanical strength,strong reliability,no rare earth permanent magnet material and fast demagnetization.However,due to its special three-dimensional structure,the magnetic circuit of claw pole generator is complicated,the magnetic leakage coefficient is high,and the magnetic leakage path is many.Therefore,it is of great significance to study the electromagnetic characteristics of the brushless claw generator for the capacity optimization of the motor.In this paper,the electric excitation brushless claw pole generator as the research object,firstly from the operation mechanism and the main electromagnetic characteristics of the generator,the first analysis of its main working principle,the mathematical model of the electric excitation brushless claw pole generator,the main magnetic circuit and the calculation formula of the rotor structure parameters.According to the motor index,the structure of the brushless claw pole generator with electric excitation is designed reasonably.After design and calculation,the reasonable structure of the motor is obtained.Then,based on the traditional two dimensional magnetic circuit method and the existing three dimensional magnetic circuit,according to the main magnetic circuit and electromagnetic characteristics of claw pole generator,a more accurate three dimensional segmented magnetic circuit is proposed.The main structure of claw pole generator is segmented processing,according to the rotor claw pole magnetic density size to the claw pole motor segment processing analysis,respectively calculate the reluctance of each segment part,according to the motor magnetic circuit to complete the construction of the claw pole motor three-dimensional segment magnetic circuit model,the electromagnetic characteristics of the motor analytical calculation.The three-dimensional finite element numerical analysis of the motor was carried out,the no-load and load characteristics of the motor were analyzed,and the rationality of the motor design was verified.At the same time,the effectiveness and accuracy of the new three-dimensional piecewise magnetic circuit were compared and verified.By comparison,the three-dimensional piecewise magnetic circuit method could be in good agreement with the finite element method in both no-load and load conditions.The calculation results of this method are accurate,magnetic leakage is fully considered,and the calculation time of three-dimensional finite element method is greatly reduced.It has great reference significance for the optimization calculation of motor.Finally,according to the three-dimensional segmented magnetic circuit,the simplified magnetic circuit of claw pole generator is obtained,and according to the simplified magnetic circuit to determine the structural parameter variables related to the base wave amplitude of the motor back electromotive force,combined with the harmonic formula of the motor,to determine the structural parameters of the motor optimization.According to the three-dimensional piecewise magnetic circuit method,the motor was scanned and calculated within the optimization range,and the change law curve of the base amplitude of the motor back electromotive force was obtained within the optimization range.The optimization range was narrowed,and then the final optimization results were determined according to the finite element method.After optimization,the voltage base wave amplitude of the generator is significantly increased,and the harmonic content of the motor is also decreased,which proves the rationality of the optimization method.To sum up,for the brushless claw pole generator,the structure design of the motor is firstly carried out in this paper,and a more accurate three-dimensional piecewise magnetic circuit model is proposed,which reduces the calculation time of finite element method.Through the three-dimensional finite element numerical calculation,the rationality of the motor structure design and the accuracy of the three-dimensional piecewise magnetic circuit were verified,and the method combining the three-dimensional piecewise magnetic circuit with the finite element method was used to optimize the motor.