The Design and Research of Speed Control System of Permanent Magnet Synchronous Motor

　　The Design and Research of Speed Control System of Permanent Magnet Synchronous Motor
　　With the appearance of high-power switching devices, analog and digital ASIC and the development of control technology, microprocessors, microcontrollers and micro-computer have witnessed the growth of AC servo system. In the AC speed drive system, the direct torque control technique is to control the motor torque directly so that the motor can perform well both in dynamic aspect and static aspect, which is also a promising way among speed drive control method. This paper talks
http://www.999magnet.com/products/131-magnetic-lifter about the speed control system of permanent magnet synchronous motor, especially about the direct torque control of permanent magnet synchronous motor and its software and hardware designs based on TMS320LF2407A DSP control system. And some issues of control system are also analyzed.First of all, the basic structure of permanent magnet synchronous motor and its types and characteristics are introduced. And then the working principle of permanent magnet synchronous motor is analyzed, on the basis of which the mathematical model of permanent magnet synchronous motor is established. Giving the theoretical basis of direct torque control system, establishing the mathematical model of permanent magnet synchronous motor, this paper constructs direct torque control system, in which the estimation of stator linkage and torque, the selection of space voltage vector and the estimation of some related parameters are all involved. Consequentially, the design of software and hardware is finished on the basis of TMS320LF2407A DSP digital control system. Finally, with the help of MATLAB simulation software, the direct torque control system of permanent magnet synchronous motor is modeled and simulated, in which the construction of all simulation modules are described. The results show that the method of direct torque control is reasonable. 更多还原

Design of Dual-Rotor Permanent Magnet Ring Torque Motor for NC Rotary Table

　　Design of Dual-Rotor Permanent Magnet Ring Torque Motor for NC Rotary Table
　　Modern CNC rotary table is needed with high torque, high accuracy, high speed ratio, until the zero-speed positioning. At the same time ask for a higher dynamic stiffness and static stiffness. When need low-speed and high torque, the induction motor and gearbox are usually combined. Gearbox is high cost, which needs repair and results in reducing the system’s efficiency and accuracy. Therefore, the removal of the gearbox is very favorable. This could be the use of permanent magnet synchronous motor (PMSM) directly to low-speed operation, and this is the so-called direct-drive permanent magnet synchronous motor. Abolished the worm wheel and worm mechanical transmission http://www.999magnet.com/products/108-alnico-magnets chain, using of direct-drive ring structure torque motor, is one of the main way to achieve high-precision CNC rotary table efficiently. In the National Natural Science Fund, the thesis studies a novel direct-drive torque motor-NC turntable dual-rotor permanent magnet ring torque motor for NC rotary table. Because of its special structure, it will have high torque density, high precision.The characteristic of direct drive permanent magnet ring torque motor is analyzed. According to the requirement of high torque density and low torque ripple, the motor application place, and practical design experience, the initial electromagnetic solution is determined, which adopts outer rotor, multi-pole, magnet surface mounted, fractional-slot non-overlapping winding, stator-cooled and so on. Considering the structure specialty and the precision requirement of the motor design, the finite element analysis method is directly applied to the electromagnetic analysis and calculation.In the way of restraining the torque ripple, the torque performance of the motor is optimized. Have an investigation on the pole-slot combinations for permanent-magnet machines with concentrated windings, choose the favorite pole-slot combinations. At the same time calculate y=1 the winding factor, and reduce the cogging torque by changing the size of inner and outer stator notch and changing inner and outer rotator pole-arc coefficient. To prove the feasibility of this method, using finite element analysis software for the torque is calculated, given the torque curve. Through the comparative analysis, prove the feasibility of this method-changing the size of inner and outer stator notch and changing inner and outer rotator pole-arc coefficient. 更多还原

Structural Optimization Design and Electromagnetic Field Analysis for the Permanent Magnet Power Magnetic Bearing

　　Structural Optimization Design and Electromagnetic Field Analysis for the Permanent Magnet Power Magnetic Bearing
　　Power Magnetic Bearing (PMB) has the ability of self-driven and self-levitated, so it can be non-contact rotation. Due to permanent magnet motor won’t need excitation current of stator winding, and possesses of high efficiency, small size, high power density and other traits, if it is combined with PMB, above advantages will be sufficiently developed, and there will be capacious foreground of applications.In this paper, Permanent Magnet Power Magnetic Bearing http://www.999magnet.com/products/142-neodymium-price (PPMB) is analyzed and optimally designed based on finite element analysis software– ANSYS, aiming at air-gap magnetic field distribution, levitation force, output torque.Two kinds of the electromagnetic force and the operating principle of PPMB are analyzed in detail, and the torque mathematical model and the levitation force analytical model is derived, when the rotor is eccentric.The choice of permanent magnet material and the design of structures of PPMB are accomplished, and the design formula of stator slot and calculation formula of turns are given. The air-gap flux wave of superfical protruding type rotor and built-in tangential type rotor are analyzed based on ANSYS, and the superfical protruding type rotor is selected at last, according to the results of the analysis.The solid model of PPMB is built using ANSYS, the suspending principle of PPMB is proved by analyzing the internal electromagnetic field.
　　The best combination of the two sets of windings is selected due to the value of radial levitation force. The parameters of the prototype is given, furthermore, the relationship of the unilateral magnetic force and the rotor eccentricity, the controllable levitation force and the current of suspension winding, the radial levitation force and the current of suspension winding are obtained, when the rotor is eccentric.The thickness, width, height of stator carcass and air-gap length are optimally designed, and the optimal size of structure of superfical protruding type rotor is obtained, which has the minimum aberration rate of air-gap magnetic field, the maximum radial levitation force, the minimum current of suspension winding and the lest volume of permanent magnet material.

A Vector Excitation Control System of a Novel Hybrid Excitation Permanent Magnet Synchronous Generator

　　A Vector Excitation Control System of a Novel Hybrid Excitation Permanent Magnet Synchronous Generator
　　The hybrid excitation permanent magnet synchronous generator(HEPMSG) has many advantages,such as simple structure and high reliability.It can realize the adjustment of field magnetic flux and expand the application of permanent magnet electrical machines.The research of the thesis focuses on the new structure of HEPMSG and the research of the control system of http://www.999magnet.com/products/131-magnetic-lifter excitation.Firstly,a novel structure of HEPMSG is proposed and its operating principle is analyzed. Secondly,a new excitation control method with i_q=0 is adopted based on the principle of vector control.The excitation current vector is controlled in the direction where permanent magnet produces the magnetic field,while the torque component of the excitation current vector equals zero.The loss of copper will be reduced and the efficiency of the generator will be improved,as the unit excitation current can produce the maximum of the field component.Lastly,a new excitation vector control system based on TMS320F2812 is designed,including the hardware and the software,and the experimental results of SVPWM debug is provided. 更多还原

Study of Shimming Method Based on the Central Magnetic Field for MRI Permanent Main Magnet

　　Study of Shimming Method Based on the Central Magnetic Field for MRI Permanent Main Magnet
　　The research of this thesis is supported by the Doctoral Program Foundation of Chinese Higher Education Institutions, Ministry of Education of China—Study of the shimming technique of the permanent magnet for open magnetic resonance imaging system(under Grant 20050142003).The system of open MRI magnet is one of the significant development aspects of medical MRI device at the present time. Its image quality is closely related with the shimming technique. The http://www.999magnet.com/products/108-alnico-magnets passive shimming with permanent MRI magnet is still a hot and difficult investigation problem. In this thesis, the research on shimming problem for open permanent MRI magnet has been presented in detail. The main work is as follows.The way of passive shimming is to shim the magnet passively, using pieces of the permanent magnetic material placed at specified locations on the pole surfaces to bring an additional magnetic field which corrects the initial field. Therefore, the numeric analysis method, analytic solving and practical measuring are presented to determine the additional magnetic field created by a single shimming sheet in this paper, which lays a foundation on the passive alnico magnets shimming process.An improved method for allowing an MRI magnet to meet its demand to the field homogeneity has been developed. The method is denoted as central shimming based on the theory of integer linear programming, which involves procedure of practical shimming and experience from shimming engineers.
　　The method proposed in the paper uses the value of central magnetic field in the imaging region to approximately correct the magnetic field of sampling points. After building the passive shimming model, the branch and bound method is adopted to optimize the shim locations and the number of shims at each allowable location which will bring the magnetic field uniformities to an acceptable level. Firstly, the numerical analysis method is proposed to compute the distribution of the magnetic field in the imaging region, which created by the shim arrays on the pole surface. Secondly, the related software is programmed to fulfill shimming steps. Thirdly, shimming is repeated based on the magnetic field corrected in the second step. The theoretical shimming scheme is obtained through combining process of the coarse and fine shimming, which is completed from outer rings to inner rings on the pole surface. In order to check the precision of the shimming algorithm proposed in this paper, shimming experiment of the queen-post permanent magnet is completed in the enterprise that produces the magnet used for MRI. According to the results comparison of measuring and computing, the validity of the method is testified finally. 更多还原

parameters calculation,Time-stepping FEM

关键词:d-q axis cross-saturation,DDPMG,improved simulation

model,parameters calculation,Time-stepping FEM
摘要:In some control strategies of the direct-rive permanent

magnet generator(DDPMG),the mathematics model is excessively

simplified and some complex nonlinear characteristics,such as

core saturation and cross-saturation,are Ball Neodymium Magnets generally neglected.To

solve this problem,this paper utilizes the frozen element

permeability method to compute the armature self-and mutual-

inductance,permanent magnet d-and q-axis flux varying with d-axis

and q-axis current,then an improved model is presented in which

the core saturation and cross-saturation between d-axis and q-

axis are considered effectively.Based on this model,the method

for computing the performance of the generators is also

proposed.Taking a 1.5-MW DDPMG http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php as an example,the time-stepping

finite element method(T-S FEM) is adopted to analyze the

performance with no-load and loaded conditions,the results show a

good agreement with the ones obtained by the improved

model.Compared with the simplified model,it is demonstrated that

the presented model has the high efficiency and reliability and

can provide a good reference for optimization design of DDPMG and

other PM motors.

quantum tunneling,magnetic coupling

关键词:lanthanide,single-molecule magnets,relaxation

dynamics,quantum tunneling,magnetic coupling
摘要:In the area of molecular magnetism,single molecule magnets

(SMMs) containing lanthanide elements are of immense scientific

and technological interest because of Block neodymium magnet their large energy barriers

and high measured hysteresis temperature.Although there has been

significant progress in the synthesis and characterization of

lanthanide-based SMMs,there are still challenges,for instance,how

single-ion anisotropy of lanthanide elements can be exploited,and

how zero-field tunneling of http://www.chinamagnets.biz/Neodymium/Block-neodymium-magnet.php magnetization can be suppressed.This

article is devoted to the progress in various methodologies for

modulating magnetic relaxation,especially in terms of crystal

field and magnetic interactions.The crystal field plays a

dominant role in creating single-molecule magnets with largely

anisotropic f-elements,while the strong coupling between magnetic

centers is able to suppress quantum tunneling of magnetization

efficiently.