Research On Module Combined Permanent Magnet Synchronous Machine With Wrapped Type For Mine Ball Mill

As an important equipment for refining and pulverizing solid materials,ball mills are widely used in metallurgy,chemical industry,cement,ceramics and other fields.During the ball mill operation,the gear is easily damaged under impact load.With the development of the large-scale ball mill,it is difficult to realize the drive system by gear transmission.In view of the problems of direct-drive permanent magnet synchronous machine for the large-scale ball mill,which is difficult to manufacture,install and maintain,and has large redundant power,this dissertation proposes a module combined permanent magnet synchronous machine with wrapped type for mine ball mill(MCPMSM).This research focuses on the structure and working principle of MCPMSM,partitioning rule,the winding analysis of the unwinding module combination structure,the analysis of electromagnetic vibration and torque distribution of different number of modules in operation,the design of modular cooling waterway structure based on the 3D equivalent thermal network method and so on.The theory is verified by prototype experiments.The main research work is reflected in the following aspects:The structure and working principle of MCPMSM are analyzed.The MCPMSM proposed in this dissertation consists of multiple modules,each of which can operate independently and is controlled by its own inverter.All inverters adopt a common DC bus power supply mode.An idea of removing coils and dividing into blocks is put forward.Part of the coils are removed under the premise of ensuring the symmetrical distribution of the windings in each module.The blank teeth are divided into blocks after the coils are removed to realize decoupling between modules.The stator partitioning rule and the uneven air gap magnetic pole structure of rotor are determined,which provides a theoretical basis for solving the problem of the motor structure design.For the eccentricity of the rotor caused by the impact load during the grinding process,a kind of wheel bearing structure is proposed to ensure the uniformity of the air gap.At the same time,the motor frame adopts hanging structure,which is convenient for each module to be wrapped around the outer circumference of the ball mill roller to realize direct drive.On this basis,the design method of the motor is summarized.A MCPMSM is designed and its electromagnetic performance is simulated and analyzed.For the convenience of the design and analysis,this dissertation introduces the concept of sub-modules.From one decoiled stator slot to the next decoiled stator slot is a sub-module,in which the number of sub-module slots is selected according to the unwinding stator partitioning rule to realize the module combination structure.Due to the change of winding distribution after removing the coils,the winding analysis of MCPMSM is carried out,and the winding distribution coefficient,electromotive force and magnetomotive force after removing the coils are calculated.The symmetry of the winding electromotive force and magnetomotive force of each module is verified by simulation,and each module can be regarded as an independent small rotating motor.The correctness of the proposed stator module combination structure and partitioning method is proved.When MCPMSM operates with different number of modules,asymmetric radial electromagnetic force will be generated,which will cause electromagnetic vibration.The radial electromagnetic force and electromagnetic vibration of the motor under different number of modules operating are studied.The loss model of a single module and the whole motor is established,and the torque distribution ratio of each module is analyzed.The mathematical model of torque distribution is established by genetic algorithm,and the optimal torque distribution method under different loads is determined.Combined with the finite element simulation results,the correctness of the proposed method and the rationality of the motor to put some modules into operation according to the load requirements are proved.In order to ensure the complete independence of stator modules,a modular cooling waterway structure is adopted.The cooling waterway between frames of each stator module is connected by a connecting pipe,and the overall cooling waterway is uniformly distributed.For the difficulty of waterway structure design and temperature rise check,the modular cooling waterway structure is designed by using 3D equivalent thermal network method and fluid-solid coupled temperature field simulation.The influence of heat capacity,water velocity and water partition thickness on the cooling effect of the motor is analyzed.Combined with the temperature rise experiment of the prototype,the effectiveness of the proposed modular cooling waterway structure design method is verified.A prototype of a module combined permanent magnet synchronous machine with wrapped type for mine ball mill is developed,which is composed of 4 modules.Each module is wrapped around the outer circumference of the ball mill roller.The frame and rotor are connected by 24 wheel bearings.The frame modules are suspended from the external bracket by connecting rods.The experimental platform is built to test the prototype,and the no-load back electromotive force of the prototype is obtained.The torque characteristics of the whole motor and the load characteristics of different modules put into operation at rated speed: output torque,efficiency and power factor are tested.The temperature rise of the prototype with modular cooling waterway structure is measured.By comparing the results of simulation and prototype experiments,the correctness and rationality of the proposed MCPMSM design and analysis methods are verified,which provides a reference for the further research of this kind of motor.