On The Control System Of Restarting At Unknown Speed With Speed-sensorless For Canned Motor For Vacuum Pump

With the development of vacuum application technology,the demand for vacuum pump is increasing in the field of large-scale integrated circuit manufacturing equipment industry,thin film technology manufacturing industry and material preparation industry.As the main driving motor of vacuum pump,the operation reliability and on-line operation time of the canned motor for vacuum pump have been widely concerned.Because of the limitation of working environment,mechanical speed and position sensors are hard to implement on the canned motor,which makes it hard to restart the motor at unknown speed.To solve the problem,this thesis research on the canned motor control system based on a 2.0k W Cage Shape and Double Canned Induction Motor for Vacuum Pump(DCIM)and a 2.0kW Canned Permanent Magnet Motor with Epoxy Resin for Vacuum Pump(CPMM),respectively.Considering the difference of the structure and operation mode between the Canned motor for vacuum pump and the conventional motor,a mathematical model of the Canned motor for vacuum pump is established.Based on the model,the speed open-loop constant voltage frequency ratio control system suitable for the DCIM and the closed loop vector control system suitable for the CPMM are built.The simulation result of output characteristics and the working characteristics of the DCIM and CPMM are analyzed.Comparing with the experimental results,the similarity between two results confirms the accuracy of the systems.Then,based on the basic control systems,using mathematical derivation,simulation and prototype experiment,the trend of transient electromagnetic torque,speed and current of Canned motor for vacuum pump is obtained when the power supply restart after cut off and the motor is still rotating.The speed estimation strategy in the sector based on the normalized stator back-EMF is designed,and a two-step restarting method of pre-restarting and restarting are determined.The control system of restarting with speed without speed sensor is established,which guarantees restarting with speed in low impact,stable and reliable characteristics.The influence of the non-ideal characteristics of the stator axis on the current growth rate,the torque ripple rate and the speed ripple rate in the pre-restarting stage are analyzed.In addition,the influence of different restarting time and power phase are analyzed.According to the analyzation,the strategy of the sector interface and the optimal point of the whole sector with low current and short stable time are determined.Finally,in view of the non-ideal characteristics of the stator axis,the mechanism of the non-ideal characteristics of the stator axis are revealed from the perspective of the conductor and winding in the motor slot,and the non-ideal characteristic coefficient is introduced to quantitatively describe the degree of the non-ideal characteristics of the stator axis.An off-line diagnosis method of non-ideal characteristics of stator axis based on standardized stator back EMF is proposed.The simulation results show that the method has good engineering practicability.In addition,a calculation model and method of the winding distribution coefficient considering the difference of the conductor distribution in the slot of the motor are proposed,and the driving performance and the electromagnetic field distribution under the non-ideal characteristic of the stator axis are given,the influence of different degree of stator axis non ideal characteristics on the driving performance and electromagnetic field of the Canned motor for vacuum pump is quantitatively studied.The above research can provide valuable reference for the establishment of more accurate motor calculation model and the formation of basic theory and technical system of high-quality servo motor system.