Analysis Of Transients At Startup Of Large Induction Motor Based On Field-Circuit Coupled Time-stepping Finite Element Method

In academic dissertation, analyze the start-up process of the large capacity of20 pole induction motor as an example.Serious core saturation and rotor bar skin effect is obvious at start up of large induction motor. For special rotor geometry,in order to analyze the impact of the skin effect of the starting process, the method of notch boundary conditions is to calculate second boundary condition at the notch according to the current of groove distribution, thereby calculating the magnetic field distribution of the rotor bars currents at different frequencies. For large-capacity motor core saturation, add a non-linear curve of permeable material in the calculation process, corresponding to the value of the B-H on the saturation region of curve binding equations of motion by linear interpolation.Based on field- circuit coupled time-stepping finite element method,establish transient analysis model of the large capacity induction motor in the case of considering core saturation and skin effect, calculated electromagnetic field distribution and current, speed, torque curve varying with time at the start-up of motor. Calculation results of this method, the calculation results of the traditional methods and test data are compared, the results show that using this method to analysis start-up process is closer to the actual value, provides an important theoretical basis of motor optimized design. Then, calculate the starting process of the motor under different circumstances, come to effect of loss caused by the skin and saturation, illustrates the effect of different initial phase of supply voltages, and the influence of different load torque on start the process of change.Finally, based field- circuit coupled time-stepping finite element methods, for the in-depth analysis of transients in a rotating induction motor the method of constant velocity is proposed, which allowed us to obtain analytical expressionsfor the currents and electromagnetic torque of the motor when selecting the d–q model as a starting point. The results of the theoretical analysis of transient currents and electromagnetic torque at the startup of the induction motor with a cage rotor are shown and the influence of the motor rotational frequency on them is determined, determines the the most favorable speed of closing. It provide a reference for the development of new large-capacity induction motor starting device.