Study On Loss And Temperature Rise Of Super Speed MW-Level Permanent Magnet Machine For Compressor

High speed machines can connect to load directly and conventional gear box is eliminated,by the way of high speed permanent machine direct drive,it not only can reduce the volume of the device,but also can reduce noise and improve efficiency of the whole system.High speed machines are widely used in applications such as natural gas centrifugal compressor,high speed machine tool,energy storage flywheel,and distributed generation system.Because rotor speed and loss density is high,the problems of rotor strength and high temperature rise are emerged,which make it difficult to study super high speed MW-level permanent magnet machine.The design experiences and rules of super high speed MW-level permanent magnet machine are lacked both here and abroad.There is a certain difficulty in design of cooling system and accurate calculation of temperature rise.Firstly,based on a 1.2MW,18000r/min super high speed MW-level compressor machine,factors on electromagnetic performances of machine are analyzed,including the structures of stator and rotor,number of poles and poles slots combination,and material of silicon steel sheets and permanent magnet and length of air gap,the design experiences and rules of super high speed MW-level permanent magnet machine are summarized.Secondly,high frequency copper loss in flat copper winding of high voltage high speed permanent magnet machine is analyzed.2D finite element method was employed to study the effects of frequency and carrier ratio,the height of the slot-opening,the position and size of the conductor and the number of strands,optimal design was taken on modified Taguchi method based on FEM to conclude the optimum ratio of width to thickness at different frequencies.Finally this paper present a new method of pole phase group coils transposition,circulating current copper loss can be obviously reduced by adopting pole phase group coils transposition connection.In addition,magnetization mode of different positions of stator core are analyzed and proposes a harmonic iron loss calculation model which consider two kinds of magnetization mode and skin effect.Inverter circuit model is build,field-circuit coupling finite element method is adopted to study the rotor eddy current loss,and the influence factors of rotor eddy current loss are studied,such as stator skew angle,the length of gap and the carrier ratio of inverter.Finally,aiming at high power density and loss density of super high speed MW-level permanent magnet machine,air cooling combined water cooling system is adopted,including shell spiral waterway and axial ventilation.Temperature field calculation model is established,the influence factor of temperature such as wind speed,water speed and the width of spiral waterway are analyzed.