Determination of the Orthotropic Material Behavior of Stator Bars and of the Material Characteristics of the Space Brackets

The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements during the design process. Hence, a material model of the complete stator bar is necessary. This paper shows the development of such a material model. The composite structure of a stator bar is quite complex and makes it impossible to provide a quick calculation of the eigenvalues. That is the reason for using a suitable, homogeneously, geometry based solid model. Special attention was paid to the experimental determination of the material characteristics of the orthotropic composite space brackets. The numerical results have been evaluated against measurements. Eigenvalues, Young＇s modulus, and shear modulus have been experimentally investigated.

Open Winding-permanent Magnet/Magnet Reluctance Hybrid Rotor Double Stator Synchronous Motor SVPWM Control

Coal mine conveyor belt and other low-speed large torque system,the torque density and torque stability of the motor requirements are higher,permanent magnet/magnet reluctance hybrid rotor double stator synchronous motor(PM/MRHRDSSM)is just adapted to this requirement,however,the traditional close winding single inverter vector control system control PM/MRHRDSSM provides large torque ripple,high speed fluctuation and large total harmonic distortion(THD)of the current,difficult to be used in actual production and life,this paper proposes a large torque open winding-permanent magnet/magnet reluctance hybrid rotor double stator synchronous motor(OW-PM/MRHRDSSM)based on SVPWM dual inverter control strategy,and analysis of open winding double inverter structure,and its voltage vector mathematical model,using the existing two-level inverter as a basis,the bilateral inverter separately discussed its role and control method,as well as the decomposition method of synthetic voltage vector and the inverter device in the small sector on-time,the end of this paper through simulation to compare the traditional close winding single inverter vector control system control PM/MRHRDSSM and the large torque OW-PM/MRHRDSSM based on SVPWM dual inverter control strategy to prove the effectiveness of the proposed method in reducing torque ripple,speed fluctuation and THD of current during motor operation.

A VSFPWM Strategy for High Frequency Torque Ripple Control of PMSM based on Stator Flux Ripple Prediction

Vector-controlled AC motor drives utilize pulse width modulation(PWM)to synthesize the desired output voltage of the voltage source inverter(VSI).In space vector PWM(SVPWM)techniques,the average realization of the space vector applying the volt-sec balance principle results in an instantaneous error voltage that generates high frequency torque ripple.It may lead to an increase in motor vibration and acoustic noise.This article presents a high frequency torque ripple prediction model based on stator flux ripple and proposes a targeted designed variable switching frequency PWM(VSFPWM)strategy to diminish high frequency torque ripple.The switching frequency is dynamically adjusted according to the peak value of the predicted stator flux ripple to mitigate high frequency torque ripple.In contrast to existing strategies,the strategy outlined in this article directly suppresses high frequency torque ripple,thus remaining unaffected by inaccurate motor parameters.Additionally,due to the introduction of the power factor angle,the proposed strategy can better adapt to the full speed range operating conditions of the motor.Detailed simulations and experiments are provided to validate the effectiveness of the proposed strategy.

Flow Field Improvement by Bowed Stator Stages in a Compressor with Different Axial Gaps Under Near Stall Condition

The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.

热老化对水轮发电机定子线棒端部主绝缘局部放电特性的影响

水轮发电机定子线棒端部主绝缘在长期运行过程中因温升及局部放电的高能粒子轰击极易发生热老化,劣化绝缘性能,加剧局部放电强度。文中根据水电站F级定子线棒绝缘结构设计制作了3种端部典型缺陷模型,在170℃环境条件下进行加速热老化;通过扫描电子显微镜和拉曼光谱分析仪对不同老化周期下的主绝缘试样进行形貌结构和分子结构分析,揭示主绝缘材料——环氧玻璃粉云母带的热老化机理;搭建局放试验平台,采用脉冲电流法和臭氧检测法测量老化前后放电量和放电次数及臭氧浓度的变化情况,并挖掘其对端部缺陷局部放电特性的影响规律。结果表明:加速热老化周期与主绝缘材料绝缘结构变化成正比,老化时间越长,试样表面越粗糙;热老化会破坏环氧玻璃粉云母带的分子链结构,苯环等芳香族和碳环上的C-C键及C=C键特征峰变化与绝缘电阻具有相关性;热老化对内部气隙放电量和放电次数的影响较小,对防晕层脱落缺陷的低放电量次数影响较大;不同绝缘缺陷模型臭氧的饱和浓度和饱和时间存在较大差异,热老化前不同放电类型的臭氧浓度变化具有阶段性,而热老化后臭氧浓度无明显的阶段性增长特征。

LOW COST IMPLEMENTATION OF SPEED SENSORLESS INDUCTION MOTOR CONTROL USING STATOR FLUX ORIENTATION

The control platform of the induction motor （IM） with low costs is developed by using DSP MC56F8013 with a good performance/price rtaio. The control algorithm for the speed sensorless IM is studied based on the stator flux orientation （SFO）. The algorithm structure is simple to be implemented and cannot be influenced by motor parameters, The improved stator flux estimation is used to compensate errors caused by the low pass filter （LPF）. A new speed regulator is designed to ensure the system working with the maximal torque in the transient state. The system simulation and the prototype experiment are made. Results show that the con- trol system has good dynamic and static performance.

Experimental Study of Stator Clocking Effects in an Axial Compressor

This paper is focused on the experimental study of the effects of stator clocking on the performance of a low-speed repeating stage axial compressor with compound-lean stators as well as the one with conventional stators （the baseline） for comparison. The experimental results show that as the clocking positions vary, the upstream stator wake enters the following passage at different circumferential positions, and then mixes with the local fluid in the following passage. This is the main reason for the variation of the compressor performance resulted from the stator clocking effects. The variation of the compressor performance due to the clocking effect is less pronounced for the compressor with compound-lean stators than with the baseline. At a certain clocking position, the efficiency of the compressor with compound-lean stators is increased in comparison with that of the baseline, especially on small mass flow rate conditions, e.g., 0.7% at design condition and 3.5% at near-surge condition in this case. The maximum 1.22% and the minimum 0.07% increases in efficiency on design condition are obtained through the combined effects of the stator compound-lean and the stator clocking in this case.

OPTIMAL DESIGN FOR STATOR OF THREE-DOF ULTRASONIC MOTOR

A 3-DOF ultrasonic motor with a cylinder-shaped stator and a spherical rotor is developed. The motor provides 3-DOF rotation around x, y, and z-axes implemented by two second order bending modes with orthogonality and one first order longitudinal mode of the stator. The three modes must satisfy some conditions. In our previous research, in order to satisfy these conditions, a parameter fitting design method is used. However, it is an experiential design method with low efficiency and costs much time, sometimes it even cannot find a desired solution. This paper puts forward an optimal design method for the stator. Based on the method, an optimization program is developed in MATLAB environment. Using the program, a new prototype of 3-DOF ultrasonic motor is designed. Its stator has diameter of 20 mm, height of 67 mm, and mass of 157 g. Experimental results show that the measured stators′ modal frequencies and modal shapes are in good consistent agreement with the results obtained by the optimal design program.

Feasibility of a New Ironless-stator Axial Flux Permanent Magnet Machine for Aircraft Electric Propulsion Application

With the development of aviation electrification,higher demands for electrical machines are put forward in aircraft electric propulsion systems.The aircraft electric propulsion requirements and propulsion motor features are analyzed in this paper.Comparing with conventional PM machines,ironless stator axial flux permanent magnet(AFPM)machine topologies with Litz wire windings allow designs with higher compactness,lightness and efficiency,which are suitable for high-frequency and high-power density applications.Based on the motor requirements and constraints of aircraft electric propulsion systems,this paper investigates a high-power 1 MW multi-stack ironless stator AFPM machine,which is composed of four 250kW modular motors by stacking in axial.The design guidelines and special attentions are presented,in term of electromagnetic,thermal,and mechanical performance for the high-frequency coils and Halbach-array PM rotor.Finally,an ironless stator AFPM motor is manufactured,tested and evaluated with the consideration of cost and processing cycle.The results show that the output power is up to 53.8kW with 95%efficiency at 9000r/min at this stage.The proposed ironless stator AFPM machine with oil immersed forced cooling proves to be a favorable candidate for application in electric aircraft as propulsion motors.

Visual study on the characteristics of liquid and droplet in a novel rotor-stator reactor

Rotor–stator reactor(RSR), an efficient mass transfer enhancer, has been applied in many fields. However,the hydrodynamic characteristics of liquid flow in RSR are still a mystery despite they are fundamental for the mass transfer performance and processing capacity. In view of the above, this paper studies the liquid–liquid flow and liquid holdup in RSR under various conditions with a high-speed camera. The paper firstly demonstrates two flow patterns and liquid holdup patterns that we obtained from our experiment and then presents in succession a flow pattern and a liquid holdup criterion for the transition of film flow to filament flow and complete filling to incomplete filling. It is found that experimental parameters, including rotor–stator distance, rotational speed and volume flow rate exert great influence on the average droplet diameter and size distribution. Besides, by comparison and contrast, we also find that the experimental values match well with our previous predicted calculations of the average diameter, and the relation between the average diameter and the mean energy dissipation rate.

THE RESONANCES OF PARAMETRIC VIBRATION WITH FORCED VIBRATION OF THE STATOR SYSTEM OF HYDROELECTRIC-GENERATOR STIMULATED BY ELECTROMAGNETISM

The resonances of parametric vibration with forced vibration isanalyzed, the bifurca- tion equation of the system is obtained andthe singularity analysis is made. Some of the laws and phe- nomenaare revealed. The transition variety and bifurcation diagram of thephysical parameteric plane are given. the results can be used inengineering.

Stator-Flux Oriented Continuous Control of Torque in Induction Motors

This paper analyzes dynamic equivalent circuit of induction motor and the relationship among inner fluxes, then presents a direct stator flux oriented continuous torque control (DSFOCTC) scheme of induction motor , which uses stator current vector control instead of voltage vector control. As a combination of direct torque control (DTC) and flux oriented vector control, it achieves round stator flux and continuous dynamic torque control resulting in less torque ripple than that in DTC. It reduces the dependence on rotor parameters, and is especially insensitive to rotor resistance. Finally, an induction motor speed control system incorporating this novel scheme is given and checked by simulation.

Application of Dual-blade Stator to Low-speed Ratio Performance Improvement of Torque Converters

With application of the lock-up clutch in the torque converter（TC）, fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed ratio performance so as to improve vehicle gradeability and launching acceleration performance. According to the results of computational fluid dynamics（CFD） analysis, hydrodynamic loss inside the stator cascade accounts for 42% of the total energy loss at stalling speed ratio. It is found that upstream flow with large impingement angle results in boundary layer separation at the leading edge, which aggregates hydrodynamic loss and decreases circular flow rate dramatically at low-speed ratio. In this paper, a dual-blade stator is proposed to suppress the boundary layer separation, which is parameterized by using the non-uniform rational B spline（NURBS） method. The mean camber line and blade profile curve are expressed by a three control points quadratic open NURBS and a cubic closed one respectively. The key design parameters included the slot width and suction side shape of the primary blade are analyzed. The most effective slot width is found to be between 4% and 8% chord length, and the boundary layer separation can be suppressed completely by decreasing distribution of momentum moment at the primary blade and adding it to the leading edge of the secondary blade. As a result, circular flow rate and impeller torque capacity is increased by 17.9% and 9.6% respectively at stalling speed ratio, meanwhile, low-speed ratio efficiency is also improved. Maximum efficiency at high-speed ratio decreases by 0.5%, which can be ignored as the work of lock-up clutch. This research focuses on using the dual-blade stator to optimize low-speed ratio performance of the TC, which is benefit to vehicle power performance.

Parameter Modeling and Kinematical Simulation for Rotor and Stator of Screw Pump

The research object used in the dissertation was screw pump, which was widely applied in engineering field. The analysis of end face profile formation was completed on its main working components, i.e., rotor and stator. With the purpose of finding optimal parameters to improve the efficiency of screw pump design, the key technologies involved in the parametric modeling of rotor and stator were analyzed. The three-dimensional (3D) design software SolidWorks was used for the secondary development and parametric modeling of rotor and stator. After that the simulation models of different kinds of screw pumps were established based on the cycloid type, variation coefficient, and screw head number. Finally the COSMOSMotion was used to analyze the motion characteristics on the equidistant line of rotor, including velocity and acceleration. This design and modeling method has been used in screw pump enterprises for design and development, laying the foundation for finite element analysis and further optimization of screw pump.

Calculation for electromagnetic torque of double-stator-permanent magnet synchronous motor

Presents the mathematic model built for double stator permanent magnet synchronous motors through a brief analysis of their future development, and the equations established for calculation of their torques, and the development of prototypes, and discusses the comparison of the motor under development with the conventional motors with the same volume, stator structure, and magnet shape, and concludes the motor under development is one of the ways to improve the performance/volume ratio of motors.

MATCH-MODE METHOD AND ITS NUMERICAL SIMULATION FOR ROTOR-STATOR INTERACTION SOURCE MODES AND PROPAGATION MODES IN AN ANNULAR DUCT WITH MULTI-TREATMENTS

The suppressing design of the engine nacelle in an aircraft can benefit from the development of the prediction system for the sound fields in engine ducts which includes the prediction of the source generation and that of sound propagation in ducts. First, the acoustic match mode principle between the source modes of rotor stator interaction noise and the propagation modes is presented in this paper. Second, by utilizing this principle, the theoretical prediction method for rotor stator interaction noise generation and its propagation and attenuation in an annular duct with multi treatments is developed. That means that the prediction of sound propagation and attenuation in the segmented ducts might no longer completely depend on the in duct mode measurements, and the investigation on the sound propagation and attenuation in ducts can be accomplished not only by acoustic mode measurement, but also by making use of the source prediction to determine the source modes excited by rotor stator interaction. The effects of fan speed, blade/vane numbers, axial spacing between rotor and stator on the in duct sound attenuation and generated sound power level before and after ducts (also including the sound power level of blade passing frequency and its harmonics at the inlet of ducts) have been numerically calculated by using this prediction method. The reliability of this prediction method is verified by reasonable agreement between the predicted results with measured results in references. By analyzing the results of calculating cases, some reference criteria are provided for the engineering design of the suppressing engine nacelle.

An Improved Stator Flux Observation Method of Permanent Magnet Synchronous Motor

The stator flux and electromagnetic torque observation is the basis of direct torque controlled permanent magnet synchronous motor( PMSM) drive system. However,the traditional stator flux observer based on voltage model is affected by integral initial values and integral drift,that based on current model is affected by the parameters of PMSM,so a new stator flux observation method is proposed based on an improved secondorder generalized integrator( SOGI). Compared to the stator flux observation method based on the conventional SOGI,the proposed method can not only overcome the influence of integral initial values and integral drift,but also completely eliminate the DC offset's influence. Therefore,the observation accuracy of stator flux is further improved. The simulation and experimental results both show that the proposed method has a higher stator flux and electromagnetic torque observation precision.

Optimizing loading path and die linetype of large length-to-diameter ratio metal stator screw lining hydroforming

In order to meet the high temperature environment requirement of deep and superdeep well exploitation, a technology of large length-to-diameter ratio metal stator screw lining meshing with rotor is presented. Based on the elastic-plasticity theory, and under the consideration of the effect of tube size, material mechanical parameters, friction coefficient and loading paths, the external pressure plastic forming mechanical model of metal stator screw lining is established, to study the optimal loading path of metal stator lining tube hydroforming process. The results show that wall thickness reduction of the external pressure tube hydroforming(THF) is about 4%, and three evaluation criteria of metal stator screw lining forming quality are presented: fillet stick mold coefficient, thickness relative error and forming quality coefficient. The smaller the three criteria are, the better the forming quality is.Each indicator has a trend of increase with the loading rate reducing, and the adjustment laws of die arc transition zone equidistance profile curve are acquired for improving tube forming quality. Hence, the research results prove the feasibility of external pressure THF used for processing high-accuracy large length-to-diameter ratio metal stator screw lining, and provide theoretical basis for designing new kind of stator structure which has better performance and longer service life.

GENERATOR VIBRATION FAULT DIAGNOSIS METHOD BASED ON ROTOR VIBRATION AND STATOR WINDING PARALLEL BRANCHES CIRCULATING CURRENT CHARACTERISTICS

Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.

Influence of Inner/Outer Stator Pole Ratio and Relative Position on Electromagnetic Performance of Partitioned Stator Switched Flux Permanent Magnet Machines

Based on the 6-pole outer stator(armature winding-stator),the influence of inner(permanent magnet-stator)/outer stator pole ratio n(n=NIS/NOS),stator relative positions and rotor pole number combinations on electromagnetic performance of partitioned stator switched flux permanent magnet(PM)machines(PS-SFPMMs)is investigated in this paper.Since the armature windings and PMs are located in two separated stators and PMs are stationary,PS-SFPMMs have high fault tolerance capabilities.To maximize the torque performance,the PM of inner stator pole should be aligned with outer stator pole when n is odd while the iron rib of inner stator pole should be aligned with outer stator pole when n is even.No matter what n is selected,the rotor pole number NR can be any integers except the phase number and its multiples.The analysis results indicate that the optimal NR is closed to(NIS+NOS)/2 and it is odd when n is odd while it is even when n is even.Meanwhile,symmetrical phase back-EMF waveform will be obtained when the ratio of Min(NOS,NIS)to the greatest common divisor of Min(NOS,NIS)and NR is even.Based on the optimal rotor pole numbers for 6-pole outer stator with different n and corresponding optimal relative position together with same rated copper loss,the average torque is improved by 18.4%,25.1%and 25.7%respectively in PS-SFPMMs with n equal to 2,3 and 4 when compared with PS-SFPMM with n equal to 1.The analyses are validated by experiment results of the prototype machine.