Loss Analysis And Optimization Design On Permanent Magnet Synchronous Motor Under Compressor Load

Compressors are incrementally employed in industrial production,as permanent magnet synchronous motor(PMSM)features good starting characteristic,low temperature rise,high frequency and well mechanical properties,PMSM,in the development tendency,emerges as the drive motor in compressor gradually.The operating principle of compressor and the design characteristics of permanent magnet synchronous motor installed in compressor are introduced in this thesis,and a PMSM with rated power of 22 kW is proposed subsequently according to the operating characteristics of compressor.On the basis of the loss characteristics analysis on PMSM in compressor,the optimization of the presented motor is fulfilled consequently.According to the design requirements and load characteristics of the compressor,the reasonable design and simulation analysis of PMSM are carried out with the field-circuit coupling theory at first,thus,the structural parameters of the motor are determined.The optimal parameters includes the pole-slot match contrasted in taking the efficiency and cogging torque as the constraint conditions,the length of air gap selected by the cogging torque,magnetic flux leakage factor and the assembly difficulty,the electromagnetic load determined through taking the electromagnetic properties,insulation and cooling conditions into account,and the rotor parameters chosen by considering the heat dissipation condition,the prototype cost and the ability of anti demagnetization.Then,the no-load characteristics and load characteristics of the proposed PMSM are analyzed,and the rationality of the design principle is verified as well.The calculation model of no-load loss and load loss in PMSM is illustrated subsequently to calculate the no-load loss,the loss increment devoted by the no-load current,the copper loss and the loss increment under the rated load.Moreover,the factors that result in the loss increment under no-load and rated load are analyzed and discussed.Though the load can be divided into constant torque load and fluctuating load,the fluctuating load is simplified into sine-wave and triangular-wave load according to the operating condition of the compressor,and the loss characteristics of PMSM under variable load are simulated and analyzed respectively.On the premise of ensuring the output torque of PMSM,the air gap magnetic distribution is optimized,including the optimization of permanent magnet structure and the optimization of the rotor lamination.Considering the segmented permanent magnet as permanent magnet of variable thickness,and the rotor lamination with non concentric circular structure is equivalent to non-average length of air gap.And the electrical characteristics,composed of the fundamental amplitude of air gap magnetic flux density,third harmonic component and its proportion to fundamental component,the harmonic distortion rate,the cogging torque and the no-load back EMF,are compared and analyzed respectively.Thus,the optimization design of magnetic flux distribution is achieved consequently.The calculation of d-axis and quadrature-axis synchronous reactance as well as the electromagnetic torque and the reluctance torque of PMSM are simulated and analyzed.On the basis of which,the structural optimization of the magnetic isolation bridge and the rotor yoke is accomplished to advance the anti-interference ability of PMSM.The simulation results represented that as the decrease of magnetic bridge width and the increment on number of rectangular holes embedded in the rotor yoke,the reciprocal difference of direct-axis and quadrature-axis synchronous reactance decreases,meanwhile,the absolute value of reluctance torque reduces as well.Thus,the anti-interference ability of PMSM improves consequently.