Research On High Efficiency And High Power Density Permanent Magnet Synchronous Motor For High Altitude Aircraft

In the field of motor application,such as solar UAV and electric vehicle,due to the limited power supply and limited load,the efficiency,volume and quality of the power source motor are all strict.The permanent magnet synchronous motor(PMSM)has the characteristics of high efficiency,small volume and high power factor.It is especially suitable for running in wide efficiency area and overload state,so as to achieve high efficiency or high power density.The efficiency and power density of the PMSM are mutual influence and mutual restriction.Quantitative analysis of the relationship between the efficiency and the power density of the permanent magnet motor is the key to achieve high efficiency and high power density permanent magnet motor.In order to solve the electric propulsion system with limited volume and quality of permanent magnet synchronous motor,high efficiency,low loss,difficult heat dissipation problems at the same time,the law of mutual influence between the the efficiency and power density on the loss,temperature rise is studied.According to the new type of ferromagnetic material lacks iron loss data,the experimental platform has been established to test the B-H curve and the iron loss characteristics of the cobalt alloy(1J22),according to the characteristics that the coefficient of the iron loss varies with the frequency,proposes a variable loss coefficient orthogonal decomposition core loss model.The finite element numerical calculation of the iron loss was carried out by using this model.The magnetic circuit calculation model of the iron loss based on the blocking stator core made of the Ferro cobalt alloy was established and the experience coefficient of iron loss was modified.The experimental results are in agreement with the numerical calculation and the circuit calculation results,which verified the correctness of the theoretical analysis.Finally,the influences of the phase current frequency and amplitude,permanent magnet charging mode and slot opening on the iron loss were studied by numerical calculation model,and the parameters which bring about the least iron loss was carried out.The air gap magnetic field of the discrete Halbach array was analyzed,and the results were compared with the numerical calculation.The research results show that when the poles and the number of per-pole magnets are greater than 4,the air gap flux is almost sinusoidal,which is the same with the ideal Halbach array.Taking into account that in the analytical calculation a lot of idealization has been done,the influence of the actual ferromagnetic boundary on the air-gap flux distribution was analyzed by the time step finite element method.The results show that the permeability and the size parameters of the ferromagnetic materials have great influence on the distribution of air-gap magnetic flux.A superposition method was proposed to calculate the eddy current loss of permanent magnet.The parameterization equation of the rotor edd y-current loss was established,which can directly analyze the influence of the motor parameters on the eddy current loss.The accuracy of the parameterization equation is verified by the finite element calculation.Finally,the influences of the permanent magnet block,the slot opening and the current change on the eddy current loss were analyzed.For the first time established the parametric equations of the copper loss,the iron loss and the eddy current loss based on the combination of the magnetic fiel d and magnetic circuit,which can quantificationally describe the variation of the efficiency and the power density influenced by the motor parameters.The parametric equations show that the efficiency is the supreme when the copper loss and the sum of the iron loss and eddy current loss is the same.The definition of "the product of the power and efficiency(PPE)" was put forward,and the parametric equation of PPE was established.The parameterization equation shows that there exists the best parameter to make the PPE maximum.The interaction rule between the efficiency and the power density of the PMSM is quantitatively analyzed.The efficiency characteristics and the power density characteristics of the inner rotor motor and external rotor motors under different load conditions were tested,and compared with the theoretical calculation results.A new motor cooling structure based on the axial heat conduction using the heat pipe has been proposed.Each part thermal resistance of the heat pipe was analyzed,and the thermal resistance model and the equivalent heat-transfer coefficient of the heat pipe were established.The equivalent model can greatly reduce the computation time of the temperature field simulation,and also ensure the precision of the calculation.Based on the equivalent motor model,the 2D thermal calculation model and the 3D thermal calculation model were established.The 3D thermal calculation model can accurately calculate the temperature field distribution,and the 2D thermal calculation model can quickly calculate temperature distribution of the main parts,for example,the armature windings,the iron core and the permanent magnets.Finally,the experimental test platform was built to test the temperature rise of the prototype under different loads and heat dissipation conditions,and the correctness of the theory was verified.