Research On Symmetrical Phase Loss And Steady-state Operation Of Nine-phase Induction Motors

The multi-phase induction motor is the core device of the ship propulsion system,which has the advantages of high reliability,high power density,and small torque ripple.For the multi-phase induction motor with multiple sets of multi-phase windings,when the propulsion system fails or sails at a low speed,one or more sets of windings can be cut out,so that the motor derates under symmetrical fault condition.In this thesis,a nine-phase induction motor composed of three sets of three-phase windings is investigated.Based on the recalculation of the stator and rotor parameters,the equivalent circuit of the multiphase induction motor is obtained under symmetrical open-circuited fault condition.The maximum output torque of the nine phase induction matched with the propeller load under symmetrical fault is calculated and the steady state performance of the motor under symmetrical fault condition is analyzed.The theoretical basis is provided for the symmetrical fault condition of the multiphase induction motor.Firstly,the magnetic potential of the nine-phase induction motor is analyzed by the traditional magnetic potential analysis method,and the vibrational magnetic potential of each phase winding is decomposed into positive and negative harmonic magnetic potentials by triangulation,so as to push the normal operation of the conductive machine.Air gap magnetic potential during symmetrical phase loss operation.The analysis results show that when the nine-phase induction motor is running in symmetrical phase loss,the fundamental magnetic potential is not distorted,it is still circular magnetic potential,the harmonic order is increased,and the remaining six-phase operation and the semi-symmetrical structure of the six-phase induction motor The harmonic magnetic potential is different.On this basis,the general expression of the synthetic magnetic potential of multiple sets of multiphase induction motors in symmetrical phase loss operation is derived.Secondly,the stator leakage reactance parameters of the symmetrical phase loss operation of the nine-phase induction motor are calculated by introducing the correlation matrix.Two kinds of correlation matrices reflecting the relationship between the phase winding and the coil side and the relationship between the phase winding and the coil are introduced,and the stator slot leakage reactance,harmonic leakage reactance and end leakage reactance are calculated respectively.The calculation results show that after cutting out the whole set of windings,the slot leakage resistance is reduced,the harmonic leakage resistance is increased,and the end leakage resistance is reduced.On the basis of recalculating the parameters,a variable-parameter T-type equivalent circuit for the symmetrical phase loss operation of the nine-phase induction motor is established.Finally,using the T-equivalent circuit,the upper and lower limits of the output torque of the symmetrical phase loss operation of the nine-phase induction motor are studied under the premise of ensuring the constant value of the stator current.The motor is determined by the coordinated adjustment of voltage and frequency.The maximum matching working point with the propeller load during the deceleration operation is further analyzed,and the efficiency,power factor and overload capability of the normal operation and symmetrical phase loss operation of the nine-phase induction motor under the same load condition are further analyzed.