Analysis And Research On Additional Loss Of Polyphase Induction Motor

Additional loss is an important part of motor loss and a key index to evaluate the performance and efficiency of the motor accurately.It is also the precondition to calculate the temperature rise of motor accurately.There are many kinds of additional losses in motor,and the causes are complicated,which have always been the focus and difficulty of motor loss calculation.This thesis mainly analyzes and studies the additional loss in core and motor parts with the method of theoretical analysis and numerical computation.The computation method of additional loss and the method of reducing consumption are explored.A field-circuit coupled nonlinear three-dimensional finite model of twelve phase induction motor is established.The three-dimensional finite element model can accurately account for the influence of the stator skew slot and radical ventilation ditch in the core on the magnetic field in the motor.By taking account of the end structure through the end resistance and the end leakage inductance establishing the most complex end model in motor can be avoid,which can reduce the number of meshes and increase the calculation speed of the model.The internal magnetic field of the twelve phase induction motor is calculated and its distribution characteristics are analyzed,which lays a foundation for the calculation of additional loss.The causes of surface loss,pulse vibration loss and inter-bar current loss caused by skew slot are analyzed.The surface loss and pulse vibration loss in the core are calculated by the analytical method and the three-dimensional finite element method respectively.An equivalent circuit network is established according to the structural characteristics of the rotor.The inter-bar current loss is obtained by solving the circuit network,and the regular pattern of inter-bar current loss with contact resistivity is analyzed.The three-dimensional eddy current loss finite element calculation models of stator clamping plate and the ventilation slot board are established,the excitation of which is set to current source.The magnetic field of the motor parts space under rated conditions is simulated by setting the initial phase angle of the rotor current,and the axial change of magnetic field caused by skew slot is considered by setting the initial angle of rotor space.The characteristics of the magnetic field and eddy current distribution of the motor parts are analyzed,which provide the theoretical basis for motor parts eddy current loss optimization.The measures to reduce the consumption of multiphase induction motors are explored.The losses in the core from both magnetic wedge and rotor geometry are optimized.The regular pattern of motor loss with both slot wedge relative permeability and rotor slot size are analyzed.The eddy current losses in motor parts are optimized from parts size,shape and material properties.The structure of stator end winding and motor parts are optimized according to characteristics of eddy current loss.This thesis provides theoretical guidance for efficiency optimization.