Research On Super Low Speed And Large Torque Permanent Magnet Synchronous Motor For Ball Mill Direct Drive

Ball mill drive system is a typical low-speed large torque system,mainly using the traditional asynchronous machine speed reducer drive mode.This paper adopts the permanent magnet synchronous motor direct drive ball mill operation,which replaces the original asynchronous motor speed reducer drive mode.Permanent magnet motor direct drive ball mill operation will bring motor power,volume,large starting torque and other parameters without considering the problem of small motor.In the design of large diameter high power megawatt pole motor should be taken into consideration.Aimed at rated power 3550 kW and rated speed 16r/min,ball mill direct drive permanent magnet synchronous motor electromagnetic is designed.By comparing the 10 poles 12 slots and 8 poles 12 slots with PMSM performance parameters,summing up the low speed and high torque slot selection law,selectting the 10 pole 12 slot unit motor pole slot combination;stator slot selection of groove and flat wire wound into the molded double coil,a permanent magnet with tangential structure arrangement type and make full use of the reluctance torque,high power density,large gain overload.The low speed and high torque permanent magnet synchronous motor for ball mill drive is optimized.With different external conditions,adding end winding motor torque density is closer to a reasonable range for the motor optimization length diameter ratio.Under certain conditions,to keep the stator diameter unchanged and observing heat load,torque density and permanent magnet volume trend for optimising stator and rotor plate size.After the rotor radius is determined,the current density is kept constantly,and the maximum torque density is obtained by optimizing the stator slot type.By means of the method of non-uniform air gap and the optimization of the magnetic pole shoulder angle,the air gap magnetic flux density is close to the sine wave.And compared with the electric motor and permanent magnet synchronous motor,the value of non-uniform air gap is obtained.The electric excitation synchronous motor is 1.5 times less than the uniform air gap,and the difference of the air gap between the PMSM is more than 2.2-2.4 times.The establishment of permanent magnet synchronous motor with eccentric ball mill model,through the analysis of air gap flux density showed that with eccentricity becomes larger,the air gap in space is not symmetric,the air gap flux density generated even harmonics,with two of the most obvious harmonic;dynamic eccentric case cogging torque introduced higher harmonic,will cause the motor torque high frequency pulse,and occurs at the early stage of dynamic eccentricity,the cogging torque does not increase significantly,when the dynamic eccentricity reaches a certain level,the amplitude increases rapidly.The different rotor eccentric state,the motor core loss and rotor eddy current loss of part of the simulation analysis shows that similar dynamic and static eccentricity effect on core loss,and the eddy current loss unlike static eccentricity eccentric obvious dynamic change.With the increasing degree of eccentricity,the eccentric rotor has a certain influence on the output torque of the motor.When static eccentric motor occurs,motor torque fluctuation change and reduce the torque fluctuation trend.But dynamic eccentricity will cause the torque fluctuation amplitude increasing.