Analysis Of Rotor Temperature Rise And Stress Characteristics Of Induction Motor Under Frequently Starting Conditions

High voltage and high power induction motor is widely used in industry because of its simple structure,good robustness and high reliability.In actual production,some special loads will require the motor to start-up frequently,and the resulting impulse current will cause the temperature rise of various parts,which seriously affects the safe and stable operation of the motor;in addition,the high-voltage and large-power stator usually uses open slots,and the tooth harmonic and frequency doubling harmonic magnetic field of the motor will also produce additional losses in the rotor during steady-state operation,resulting in the temperature rise of the rotor If it is too high,it is easy to cause broken rotor bars.Therefore,in order to avoid the broken rotor bars under such working conditions,this thesis carries out systematic research on the rotor temperature rise and stress of high-voltage and large-power induction motor which starts frequently1)The electromagnetic and loss characteristics of induction motor during start-up and steady-state operation are analyzed by using self-developed time stepping finite element software;the three-dimensional finite element model of temperature rise stress field of high-voltage and large-power induction motor is established,and the coupling analysis of temperature rise stress field is realized;taking a 22KW induction motor as an example,the effectiveness of the established model is verified through loss and rotor temperature rise experiments And its correctness.2)Aiming at the broken bar phenomenon of 6kV,1600kw induction motor for circulating water pump in auxiliary system of a thermal power plant under frequent starting conditions,the loss of stator and rotor,temperature rise and stress characteristics of rotor during starting and steady-state operation were calculated and analyzed by using the above-mentioned finite element model;the root cause of broken bar easily occurred in the connection area between rotor guide bar and end ring was revealed,so as to avoid the damage of rotor The theoretical foundation is established for the optimal design of the broken bar.3)A rotor harmonic elimination slot structure suitable for high-voltage and large-power induction motor is proposed.The key parameters of harmonic elimination slot structure,rotor slot size and air gap length are optimized,and the electromagnetic,temperature rise and stress distribution characteristics before and after optimization are compared.Furthermore,the proposed harmonic elimination slot structure is applied to a 6kV,1600kw motor,and the temperature rise before and after improvement is measured on site The results show that the proposed bar structure can effectively reduce the temperature rise of the rotor and the whole motor,avoid the rotor bar breaking fault,and obtain good application effect.