Demagnetization Mechanism And Operating State Analysis Of Double Rotor Double Squirrel Cage Permanent Magnet Induction Motor

Structurally,the dual-rotor permanent magnet induction motor is provided with a permanent magnet rotor inside the rotor of the conventional induction motor to provide an excitation magnetic field for the motor.The double squirrel cage winding is used,and a magnetic bridge is set between the inner and outer squirrel cages,and the permanent magnetic field magnetic flux and the stator magnetic field flux are partially interlinked by the magnetic bridge and the cage winding,thereby improving the main magnetic circuit.In this thesis,a new type of Dual-rotor Double-squirrel-cage Permanent Magnet Induction Motor is studied.The main work is as follows:1.Establish a calculation model that can comprehensively consider the stator armature magnetic field,the rotor squirrel-induced magnetic field and the permanent magnet magnetic field.The effects of load torque,moment of inertia and initial position of the permanent magnet rotor and power supply voltage on permanent magnet demagnetization during starting to be analyzed.The shielding effect of the double squirrel cage windings was investigated by the time-step finite element method.The demagnetization region of the motor under extreme working conditions is determined,and the steady state performance of the motor before and after the local irreversible demagnetization of the permanent magnet is compared and analyzed.2.Through the finite element analysis of the steady-state characteristic parameters of the motor and the change of the magnetic stability of the permanent magnet,the abnormal operating conditions such as out-of-step,reclosing,phase failure and reversal are obtained.The influence of demagnetization reveals the relationship between the operating control parameters such as the mechanical load on the motor,the timing of the reclosing,and the voltage exchange timing in the reverse state,and the degree of demagnetization of the permanent magnet.3.Explore the effects of the load-carrying mode on the steady-state operating characteristics of DDPMIM and the demagnetization of permanent magnets during starting.The minimum value of the magnetic flux density at the reference point of the permanent magnet during the starting process under load distribution ratio is simulated and the influence of the load distribution ratio on the demagnetization of the permanent magnet is analyzed.The influence of the load distribution ratio on the characteristic parameters such as the efficiency and power factor of the steady-state operation of the motor is studied.The influence of the load factor is also considered in the analysis process.4.The three-dimensional global temperature field of DDPMIM was analyzed by an electromagnetic field-temperature field coupling analysis method.The DDPMIM electromagnetic field model and the three-dimensional temperature field model are established.The heat source density of each component of the motor is calculated according to the loss of each component obtained by the steady-state operation of the electromagnetic field,and the calculated heat source density is used as the thermal parameter of the temperature field to determine the temperature distribution of the components of the DDPMIM.The temperature field analysis during stable operation of the DDPMIM permanent magnet rotor under rated load was synchronized with the model under the rated load of the squirrel cage rotor and compared for comparison.The temperature distribution of the motor in the squirrel cage/permanent magnet rotor under different loading modes and the change of the overall temperature of the motor after the irreversible demagnetization of the permanent magnet are examined.Through the above research,the data reference is given for the temperature distribution of the permanent magnet motor after demagnetization.