| With the rapid development of electric vehicle industry,permanent magnet synchronous machine has been widely used because of its high power density,wide speed range,etc.in recent years.During operation of the vehicle,the operating point of the machine affected by load and control changes with real time.The traditional design methods which focus on the nominal operating point could not meet the design requirements of the machines applied on a wide speed range in electric vehicle.With the complex interaction of space and time harmonic wave,the accurate predictions of machine losses also face significant challenges.Therefore this thesis presents deep research on the calculation methods and key technologies of stator core losses,rotor losses,copper losses and thermal modeling of the permanent magnet synchronous machines within a wide speed range.And the improved calculation and design methods have been provided.First,a universal precise analytical model of stator core losses is proposed based on the distribution of windings and pole-slot combination under vector control,in which the impact of space harmonics and time harmonics has been taken into account.The on-load and no-load flux density waveform of air gap and other parts can be accurately calculated with the impact of armature reaction magnetic field and air gap magnetic permeance in the surface-mounted PM machines.Then the stator core losses could be got by formula equations.By comparison with finite element simulation results,the accuracy of the proposed method has been verified.The finite element method has been used to calculate the stator core losses of different pole-slot machines.The correction factor to consider the impact of the rotating magnetic field is used to correct the results and improve the accuracy of the stator core losses of machines.The magnetic field and stator core losses of interior I-shaped PM machine have been analyzed of the excitation voltage source SVPWM under the maximum torque per ampere and field weakening control.And the validity of the calculation method has been verified by testing data.Secondly,according to the derivation and analysis of MMF generated in the rotor yoke caused by slot harmonics,a method has been designed to optimize the double-layer PM rotor structure to reduce the rotor core losses.The electromagnetic field numerical analysis method has been used to analyze and calculate the rotor magnetic field and eddy current losses of the I-shaped PM machine under field weakening control,mainly caused by time harmonics.According to the foregoing analysis of the rotor,the structure of rotor has been optimized.And a comparative analysis of the rotor magnetic field and eddy current losses has been presented in the V-shaped and double-layer PM machines.Again,an electromagnetic design process method based on vector control of permanent magnet synchronous machines has been proposed.Proposed electromagnetic design method discusses the way to reduce the copper losses in the whole power range of machine.According to the theoretical derivation and calculation,the relationship of back EMF and copper losses provides the approach to reduce the copper losses of machine in the whole power range.Meanwhile,in consideration of the machine saturation,a constant inductance has been used during the control.The analysis results reveal the influence of different constants inductor and copper losses.Finally,a three-dimensional temperature field calculation model considering the actual winding-end has been build to improve the accuracy of the finite element model of the water-cooling machine.The temperature rise of the machine at rated load has been calculated.Comparing with experimental results,the experimental and theoretical analysis results show good consistency.The influence of the copper losses,stator iron losses and rotor permanent magnet eddy current losses on the highest temperature rise and the highest temperature inside the machine has been studied.Transient temperature field method has been used to calculate the temperature rise limit under overload situation to obtain the maximum operating time of machine,which could help to estimate the thermal state of the machine overload. |
