Research On Dynamic Starting Characteristics Of Canned Solid-rotor Induction Motor

As a key component of canned pumps used in aerospace,chemical industry,nuclear power generation and other fields,canned motors play a pivotal role in the transportation of liquid without leakage.The structure and characteristics of canned solid-rotor motor with squirrelcage are suitable for pumps.However,during the start-up process,the current between the rotor can,rotor bars and solid-rotor varied with the speed and frequency,showing the characteristics of time-varying and strong coupling.The complex current distribution,especially the interaction between the solid-rotor and rotor bars,is difficult to calculate and has a great influence on the start-up characteristics.This paper takes canned solid-rotor induction motor with squirrel-cage as the research object,focusing on the start-up characteristics.First,combined with the structural characteristics of canned solid-rotor induction motor with squirrel-cage,a two-dimensional multi-layer analytical model,considering the rotor side magnetic field saturation and the skin effect when the motor is started,was established to calculate the equivalent circuit parameters.Meanwhile,considering the mutual coupling effect of the induced current in the rotor can,rotor bars and solid-rotor,the phase winding equation was established.Then the relationship between the parameters of the phase winding equation and the equivalent circuit was calculated.Then,an analytical calculation model,taking the influence of the induced current of rotor yoke into account,was established to calculate the rotor bar current density,which shows an asymmetric U-shaped distribution during start-up process of two-pole motor.The accuracy was verified by comparing with that of the finite element simulation when the motor was started under different voltages,which provided reference for accurate calculation of parameters and performance of the motor.An experimental prototype was established to verify the accuracy of the modification of performance calculation according to the current distribution of the bar.Meanwhile,based on the equivalent circuit,the effect of the resistivity of the solid-rotor on the starting characteristics of the motor was studied,which provided theoretical guidance for the selection of the material of the rotor while optimizing the start-up characteristics of the motor.Finally,combining the electromagnetic field calculation and the state space equation,a calculation program was developed to calculate the equivalent circuit parameters,the state space equation parameters and the start-up characteristics.To analyze the current and flux variation of parallel branches in stator side during starting process,the branch analysis model and multi-loop model is established.At last,a two-dimensional finite element analysis model was established to verify the accuracy of the calculation results of the program.