Research On Direct Drive Permanent Magnet Motor For Crane Application

Traditional cranes are mostly driven by asynchronous motors and reducers,but they have many disadvantages,such as: complex structure,long drive chain length,frequent maintenance,unreliable operation,low efficiency and power factor of asynchronous motors,environmental pollution due to oil leakage of reducers,etc.Obviously,it is no longer suitable for the requirement of energy saving and emission reduction in contemporary society.However,the new trend of crane development is using low-speed and high-torque permanent magnet synchronous motor(PMSM)to directly drive cranes.Aiming at the harsh working conditions(such as steel plants)of the crane,and its frequent starting,large load range,as well as the shortterm working characteristics,the following research has been done:(1)The electromagnetic scheme of PMSM for direct drive cranes is given.Compare the effects of three types of pole-slot combination on the no-load air-gap magnetic density,backEMF,cogging torque and output torque of the motor,and select the optimal pole-slot combination.Then,optimizing motor cogging torque and no-load air gap magnetic density is required.Firstly,analyze various parameter factors affecting the optimization goal by the analytical method.Secondly,through the PB experiment design,screen out the factors that have significant effects.Next,through the CCF design in the response surface method,the relationship between the significant factors and the optimization objective is studied,which is fitted into the objective function in the form of polynomial.And the NSGA ? optimization algorithm is implemented to calculate the Pareto frontier.Finally,the optimized parameters are verified by finite element calculations,and the optimized scheme of the PMSM of the direct drive crane is determined.(2)Aiming at the characteristics of frequently heavy load starting,frequently start and stop,and overload operation of cranes,the magnetic fields of the motor under different loads are studied.Due to the loading characteristics of the crane,the motor is prone to magnetic saturation.The effects of magnetic saturation on the performance of the motor and its control system are studied in this paper.First,given the different load currents,study the effect of magnetic saturation on the orthogonal axis inductance and the permanent magnet flux linkage.Then,reestablish the model of PMSM considering the magnetic saturation.Establish vector id = 0 control model considering the magnetic saturation,perform the simulation analysis with different loads,and compare with the model that ignores the magnetic saturation to summarize the influence of the magnetic saturation on the motor control.(3)Considering the installation size of the motor on the crane,it is necessary to minimize the size of the motor and increase the torque density.The designed motor scheme uses water cooling.This paper studies the effect of different water channels on the heat dissipation of the motor,and calculates the equivalent thermal conductivity of the water channel structure parameters and air gap according to the formula.Besides,this paper also analyzes and calculates motor losses,and applys a heat source to the motor.Fluid-solid coupled heat transfer calculations for motors are carried out by fluent,and the rationality of the temperature rise requirements of the motor was verified.