Research On Modular Wrap Direct Drive Permanent Magnet Motor For Cement Mill

As a traditional processing equipment in the cement industry,the mill has a history of more than 100 years.At present,most cement mills adopt the transmission mode of asynchronous motor-reducer-open gear-mill cylinder.This kind of drive system has poor efficiency,low power factor,long transmission chain,and requires frequent maintenance.The power of the gear transmission system The upper limit restricts the enlargement of the ball mill.A high-efficiency drive system can be realized by directly driving the cement mill with a low-speed and hightorque permanent magnet motor.Aiming at the problems of low speed and high torque direct drive permanent magnet motor for cement mills,such as large volume and difficult installation and transportation,this paper analyzes a modular wrap direct drive permanent magnet motor for cement mills.Including the analysis of the modular winding with incomplete coils,the modular wrap structure and the modular Z-shaped waterway adopted by the motor.The main research contents are as follows:Modular wrap direct drive permanent magnet motors use modular windings with incomplete coils.Modular winding is to remove a part of the coils of fractional slot concentrated winding,and make it equally divided into multiple module windings,each module is powered independently,and the modules are electrically decoupled.In this paper,the stator magnetomotive force of the modular winding with incomplete coils is calculated,and the harmonic order of the stator magnetomotive force is analyzed.After the coil is installed,it still corresponds to the number of poles of the original motor rotor.The no-load back EMF,electromagnetic torque and thermal load of the modular winding motor and the conventional winding motor are compared,and the design characteristics of the modular wrap direct drive permanent magnet motor are analyzed.A four-module wrap direct-drive permanent magnet motor is designed,its electromagnetic performance is simulated,and the motor inductance parameters and starting performance are analyzed.The modular wrap structure divides the stator core and the casing into stator modules at the coil removal position to achieve mechanical decoupling.Each module is wrapped around the outer circumference of the mill and connected,and installed in the stator support frame.The wheel bearing is used to maintain the air gap between the stator module and the rotor,which solves the problem of rotor eccentricity.The stress of the rotor support is analyzed and simulated,the vibration frequency of the mill barrel is calculated,and the vibration mode of the stator structure is simulated to avoid the problem of insufficient structural strength and resonance.The loss of each part of the motor is simulated and analyzed,and a modular Z-shaped water circuit is designed to simulate the temperature condition of each part of the motor.Design and manufacture a four-module wrap direct-drive permanent magnet motor prototype of a cement mill,and build an experimental platform for experiments.The no-load back EMF of the prototype and the efficiency and power factor at rated speed were tested.The rated temperature rise at different positions of the motor was tested.The test results are compared with the theoretical calculation results,and the theoretical calculation results are basically consistent with the experimental data.