| Multi-phase induction motors are widely used in ship integrated electric propulsion systems because of their high torque density,fault tolerance,and easy to meet large capacity requirements.Among the various types of losses of multi-phase induction motors,copper loss accounts for the highest proportion,and some additional copper loss is difficult to measure directly.For this reason,this paper studies the stator and rotor copper loss of multi-phase induction motors in depth,and the twelve-phase induction motor is used as an example for analysis and calculation.In order to calculate the basic copper loss of the prototype,the calculation formulas of the stator and rotor resistance of the multi-phase induction motor structure are given.At the same time,the skin effect of the conductor in the stator slot of the prototype is analyzed,and the resistance increase coefficient different number of conductors in the stator slot are calculated;the skin effect coefficient of the prototype rotor bar is calculated by the layered method instead of the traditional analytical formula method.This method is not only suitable for the copper loss analysis of the complex shape rotor,but also can be programmed by computer numerical calculation software,and it is convenient.In order to calculate the additional copper loss of the multi-phase induction motor rotor under non-sinusoidal current,based on the layering method,the calculation formula of the loss under non-sinusoidal current is further derived.The derivation results prove that the copper loss in rotor generated by non-sinusoidal current equals the sum of copper loss generated by each frequency current;the reduction of the rotor of the prototype is carried out from the two factors of slot matching and rotor slot height,and an optimization scheme for effectively reducing the copper loss of the prototype rotor is given,which improves the efficiency of the motor.lay the foundation.In order to reduce the additional copper loss of the stator winding,the strands in the stator slot are transposed to solve the problem of current density unevenness caused by the skin effect and the proximity effect.Based on the leakage inductance method.The leakage inductance calculation formula of the stator winding with multiple turns wire bar structure under the 360° transposition mode is calculated,and the strand circulation and circulation loss under three transposition angles are calculated.The multi-section field-coupling finite element method is used to verify the calculate the validity of the formula.In this paper,the calculation method and the reduction measures of the multi-phase induction motor stator and rotor copper loss are valid and validated by simulation,which can provide theoretical basis for the loss analysis and optimization design of multi-phase induction motor. |
