Research On Optimization Design Of High-Speed Permanent Magnet Generator Applied To Micro Turbojet Engine

Because of the high speed and the tough working environment of micro turbojet engine(MTE),it is difficult for the ordinary motor to apply in it.The high-speed permanent magnet generator(HSPMG)has a remarkable technical superiority in MTE's application due to its performance characteristics such as high speed and small volume.This article will focus on the structure design scheme and calculation methods for the electromagnetic parameters,such as the no-load induction electromotive force(EMF),the inductance,the magnetic field distribution of the core and the iron loss.In this paper,the electromagnetic optimization design method of the HSPMG for MTE are studied too.This article proposes the structure design schemes of the stator and rotor,based on the small scale and high speed of HSPMG,and the initial size design of the HSPMG applied to MTE is carried out.In order to improve the simulation efficiency of the back EMF and inductance,this paper proposes an improved electromagnetic parameter calculation method calculating the back EMF by air-gap static flux density distribution and calculating the coil average inductance at quadrature-direct axis midline(Gap Flux Density-Average Inductance Point,called GFD-AIP).Compared with the traditional electromagnetic parameter calculation method,this method shortens the design period of high speed generator,simplifies the design process and improves the working efficiency.In this paper,an iron loss calculation model suitable for high frequency working condition is established based on loss compositions of silicon steel sheet and the mechanism of each composition.In order to reduce the workload of iron loss calculation and to avoid the change of the unit element and node information caused by the repeated reconstruction of the model when obtaining the iron core magnetic flux density time domain waveforms,the time domain magnetic field calculation model based on slip boundary is presented.This paper also researched the iron loss distribution under the conditions of different iron core materials,different stator structure sizes and different rotational speeds.This paper combines the GFD-AIP electromagnetic parameters calculation method with the gradient descent optimization method,and proposes an improved gradient descent optimization method based on GFD-AIP method(called GDGFD-AIP method)to research the minimum volume optimization design of generator.Finally,based on the GDGFD-AIP optimization method,several high-speed generator prototypesfor MTE are designed,and the test platform for the electromagnetic parameters and iron loss of the HSPMG is established.The correctness and efficiency of the iron loss calculation method based on slip boundary condition in this paper is verified by testing the back EMF and inductance of the generator and the stator iron loss at different speeds.