Analytical closed-form investigation of pwm inverter induction motor drive performance under dc bus voltage pulsation

The voltage unbalance conditions at the input rectifier stage of the AC?DC?AC rectifier-inverter fed induction motor drive is analysed. This unbalance can cause significant voltage harmonic of twice the line frequency 2f1 in the DC bus. This voltage ripple can have a degrading effect on the induction-machine performance characteristics. The authors present an analytical closed-form mathematical model and analysis of the impact of DC bus ripple voltage of the three-phase voltage source inverter with the space-vector PWM on the induction machine phase voltages, currents and torque pulsations. The analytical expressions for the voltage and current space vectors as a function of the DC bus voltage pulsation are derived. Using superposition, the separate parts of the motor currents can be determined. From the current space vectors, the torque behaviour is estimated, again as a function of DC link voltage pulsation. Next, it is shown that the DC link voltage ripple components may cause large torque pulsation. The proposed analytical method is based on the mixed p?z approach, enabling presentation of the results in lucid and closed form. To verify the effectiveness of the proposed analytical model, experimental results based on laboratory setup were obtained.     

Control of a converter system for an asymmetrical parameter type two-phase induction motor drive operating in motoring and generating modes

The control of a converter system is presented and discussed for an asymmetrical parameter type two-phase induction machine drive that is operating in motoring and generating modes. The proposed system consists of back-to-back voltage source converters. For a machine side, a three-leg voltage source converter provides both unbalanced and balanced two-phase output voltages with a scalar V/F control based on a carrier space vector pulse width modulation (SVPWM) technique. For a front end, a single-phase AC/DC doubled voltage converter with hysteresis current control is used to keep DC-link voltage constant, thus resulting in a bi-directional power flow operation for the motoring and generating modes. A closed-loop design for the DC-link voltage is fully given and also included is a review of carrier-based SVPWM for two-phase three-leg VSI. The proposed drive system was both simulated using MATLAB/SIMULINK and implemented on digital microcontrollers. The comparative performance evaluation of the whole system between balanced and unbalanced two-phase voltages for the machine is given. The simulation and experimental results show that the unbalanced phase voltage offers better performance for the whole system.     

Sensorless Monitoring of a Motor-Drive Machanical System Based on Adaptive Signal Decomposition

1IntroductionSensorless techniques have been successfully applied to motor speed measurement, noise and vibra-tion identification, and machinery fault diagnosis. Although a variety of relevant techniques such asvibration analysis are nowavailable for the monitoring and diagnosis of a mechanical system, studiesof the sensorless techniques have been followed with great interest by many researchers. In the tech-nique, since the motor is regarded not only as a drive motor to provide mechanical ene…     

Design of a wound-field flux switching machine with dual-stator to reduce unbalanced shaft magnetic force

Abstract

This paper presents the design and experimental verification of an outer-rotor, wound-field flux switching machine for in-wheel traction applications. The 12-stator slot, 7-rotor pole topology was selected because it produces higher torque and fewer back-electromotive force voltage harmonics than the other topologies. The machine was designed on the basis of the physical dimension limitations for in-wheel traction in a lightweight electric scooter. Because this machine exhibits shaft radial magnetic force caused by the odd rotor poles, a novel dual-stator motor structure is proposed to reduce this force. The finite element analysis calculation results demonstrated that the shaft radial force can be reduced to nearly 0 with this design, whereas the generated torque reduced only by 3%. The effectiveness of the design was also verified through the experiments that compared the vibrations of the original and the dual-stator motors. The vibration of the dual-stator motor was substantially lower than that of the original motor.     

On-line mechanical unbalance estimation for permanent magnet synchronous machine drives

An on-line mechanical unbalance estimation for permanent magnet synchronous machine (PMSM) drives is presented. At high speeds, either rotor or mechanical load unbalance generates vibration that can cause mechanical failure such as a defect of a bearing or shaft. To prevent failure and minimise mechanical vibration, the amount of the rotating unbalance should be detected in real time. The information of the estimated unbalance can be utilised to manage an operation to achieve the durability of mechanical parts. The dynamic nature of a mechanical system with a PMSM with regard to unbalance is investigated. From this examination, the models of the stator current in time and frequency domains for PMSMs are presented to develop a robust real-time unbalance estimation scheme. Based on the modelling and analysis of a rotating mechanical system using a PMSM drive, a compact unbalance estimation algorithm is proposed. The algorithm is combined with an open-loop torque observer and an unbalance estimator using a filter. Experimental results show the validation of the developed model and the proposed on-line unbalance estimation scheme.     

Characterization and Reduction of Magnetic Noise Due to Saturation in Induction Machines

This paper derives the analytical characterization of Maxwell radial vibrations due to saturation effects in induction machines, and especially in traction motors. The number of nodes and the velocity of these particular force waves are experimentally validated by visualizing some operational deflection shapes of the stator. It is shown that according to the stator and rotor slot numbers, and stator natural frequencies, these forces can be responsible for high magnetic noise levels during starting and braking. A simple rule to avoid saturation magnetic noise is then proposed, and applied to an industrial motor. Simulation results show that the new proposed motor improves magnetic noise level up to 20 dB, whereas experiments give a 15 dB improvement.      

Analysis of a stand-alone three-phase selfexcited induction generator with unbalanced loads using a two-port network model

This work proposes an equivalent circuit model for a stand-alone three-phase self-excited induction generator (SEIG) with unbalanced load impedances. The SEIG supplying unbalanced loads is modelled by a two-port network that allows the steady-state performance of the generator to be analysed more easily and more efficiently. The proposed model is validated by experiments on a 0.5 Hp cage-type induction motor operated as a generator.     

偏心故障下动车组牵引电机转子振动特性分析

气隙偏心和质量偏心是动车组牵引电机中普遍存在的两类偏心故障,而由此产生的不平衡磁拉力和机械不平衡力常诱发更为复杂的转子动力学行为,危害列车牵引驱动装置的安全可靠运行。为此,该文建立了静动气隙偏心和转子质量偏心下牵引电机转子系统的Jeffcott模型;推导了静动气隙偏心下牵引电机带负载运行时气隙磁密分布和转子铁芯表面Maxwell应力分布,并给出了可适用于静动气隙偏心、空载/负载运行和任意磁极对数的电机不平衡磁拉力统一解析表达式;采用四阶定步长Runge-Kutta算法计算了某型动车组牵引电机转子在不平衡磁拉力和机械不平衡力作用下的动力响应,并详细讨论了初始静偏心、质量偏心、径向刚度以及转速对系统振动特性的影响规律。结果表明:偏心故障下该型牵引电机转子轴心轨迹呈现接近圆形的椭圆状,其中质量偏心、径向刚度和转子转速会影响轴心轨迹大小,而初始静偏心和径向刚度则使轨迹中心沿静偏心方向偏移。同时,气隙偏心的存在使得具有质量偏心故障的电机转子位移频谱中较明显地包含零频、转频、固有频率、二倍转频、二倍供电频率及其与转频的组合等分量。     

A rotary ultrasonic motor using bending vibration transducers

A rotary ultrasonic motor using bending vibration transducers is proposed. In each transducer, two orthogonal bending vibrations are superimposed and an elliptical trajectory is generated at the driving foot. Typical output of the prototype is a no-load speed of 58 rpm and maximum torque of 9·5 Nm under an exciting voltage of 200 V(rms).     

Negative sequence compensation within fundamental positive sequence reference frame for a stiff micro-grid generation in a wind power system using slip ring induction machine

An isolated wind power generation scheme using slip ring induction machine (SRIM) is proposed. The proposed scheme maintains constant load voltage and frequency irrespective of the wind speed or load variation. The power circuit consists of two back-to-back connected inverters with a common dc link, where one inverter is directly connected to the rotor side of SRIM and the other inverter is connected to the stator side of the SRIM through LC filter. Developing a negative sequence compensation method to ensure that, even under the presence of unbalanced load, the generator experiences almost balanced three-phase current and most of the unbalanced current is directed through the stator side converter is the focus here. The SRIM controller varies the speed of the generator with variation in the wind speed to extract maximum power. The difference of the generated power and the load power is either stored in or extracted from a battery bank, which is interfaced to the common dc link through a multiphase bidirectional fly-back dc-dc converter. The SRIM control scheme, maximum power point extraction algorithm and the fly-back converter topology are incorporated from available literature. The proposed scheme is both simulated and experimentally verified.     

Performance of high speed air spindle motor equipped with composite squirrel cage rotor

The dynamic characteristics of a built-in motor type air spindle system can be improved by the reduction of mass of squirrel cage rotor because the critical whirling vibration frequency of a high speed air spindle system is highly dependent on the rotor mass of motor and the spindle specific bending modulus. In this paper the rotor of an AC induction motor was manufactured using magnetic powder containing epoxy composite whose density is half of conventional metal rotor and the motor shaft was made of high modulus carbon fiber epoxy composite material. In order to enhance the magnetic flux of the composite squirrel cage rotor of the motor, a steel core was inserted into the composite rotor. The magnetic behavior of composite squirrel cage rotor was analyzed with respect to shapes and positions of the conductor bars and the steel core of the rotor, and the optimal configuration for the dynamic performance of the rotor system was proposed.     

Single-current-sensor-based active front-end-converter-fed four quadrants induction motor drive

Induction motor (IM) is a workhorse of the industry, whose dynamics can be modified close to that of a separately excited DC machine by field-oriented control technique, which is commonly known as vector control of induction machine. This paper presents a complete performance of the field-oriented control of IM drive in all four quadrants with a single-current-sensor-based active front end converter whose work is to regulate DC link voltage, draw pure sinusoidal currents at unity power factor and to facilitate bi-directional power flow between the grid and the drive. The entire system is completely modelled in MATLAB/SIMULINK and the results are discussed in detail. The vector control analogy of the back to back converters is highlighted along with the experimental results of field-oriented control of induction machine using a dsPIC30F6010A digital signal controller.     

基于自适应滤波的电主轴-刀具系统不平衡振动的主动控制

为了有效抑制由质量不平衡引起的电主轴-刀具系统的不平衡振动,本文提出了一种基于最小方差的分块(FBLMS)自适应滤波的电主轴-刀具系统不平衡振动的主动控制方案,该控制方案中用来抑制振动的力源于无轴承电机径向磁悬浮力产生的原理。本文首先研究了双绕组感应型电主轴的结构及工作原理和径向控制力的模型,借助有限元法建立了感应型柔性电主轴-电主轴-刀具系统的动力学模型以及研究了FBLMS自适应滤波控制算法,设计了感应型柔性电主轴-电主轴-刀具系统不平衡振动的主动控制系统,通过有限元法来确定径向控制力的系数以及单边磁拉力的系数,研究了经典PID控制器以及FBLMS自适应滤波控制器对刀具端的不平衡振动的控制效果,结果表明采用FBLMS自适应滤波控制器对抑制电主轴-刀具系统端不平衡振动具有更佳控制效果。     

FPGA-Based Multiple-Channel Vibration Analyzer for Industrial Applications in Induction Motor Failure Detection

Early detection of failures in equipment is one of the most important concerns to industry. Many techniques have been developed for early failure detection in induction motors. There is the necessity of low-cost instrumentation for online multichannel measurement and analysis of vibration in the frequency domain, and this could be fixed to the machine for continuous monitoring to provide a reliable continuous diagnosis without needing trained staff. Field-programmable gate arrays (FPGAs) are distinguished by being very fast and highly reconfigurable devices, allowing the development of scalable parallel architectures for multichannel analysis without changing the internal hardware. The novelty of this work is the development of a low-cost FPGA based on a multichannel vibration analyzer; this is capable of providing an automatic diagnosis of the motor state carrying out online continuous monitoring. To test the functionality of the proposed vibration analyzer, three experiments on 746-W (1-hp) induction motors were carried out. Such experiments are intended to detect motor failures such as broken bars, unbalance, and looseness. The obtained results show the overall system performance.      

Automatic induction machine parameters measurement using standstill frequency-domain tests

A new method to measure the induction machine equivalent circuit parameters is proposed. The method is based on three frequency-domain tests, performed at standstill, avoiding then the locked-rotor and no-load tests. The proposed algorithm can be implemented in standard motor drives in order to automatically perform self-commissioning. Furthermore, the proposed method allows a direct measurement of the iron saturation. Experimental results are presented to validate the measurement method and the machine equivalent circuit.     

Pressure Vessel Wall Thinning Detection Using Multiple Pairs of Fiber Bragg Gratings For Unbalanced Strain Measurements

This paper proposes a method for using a pair of identical fiber Bragg gratings to measure the unbalanced strain factor in an isothermal-mechanical system. Cascading two identical fiber Bragg gratings, the unbalanced strain factor caused by the disturbance can be interrogated from the peak difference of the two reflecting Bragg wavelengths. If the mechanical system is in an isothermal environment, the thermal variations in the Bragg grating detection system can be automatically compensated. To verify the feasibility of the unbalanced strain detection using a pair of fiber Bragg gratings, the wall-thinning monitor in a pressure vessel system was investigated. The proposed technique is easy to install, immune to electro-magnetic and thermal interference, and highly sensitive in-time to remote monitoring for fiber optic smart structures.A finite element model (FEM) is used to simulate the wall thinning in a pressure vessel system. The minimum detectable unbalanced strain and cross-talk between two reflecting Bragg wavelengths were investigated.ROC Revised for Journal of Nondestructive Evaluation, 2000     

Use of the infrared data for heating curve computation in induction motors: Application to fault diagnosis

Infrared thermography is a technique that has been frequently used as a predictive tool for electrical installations maintenance, since many of the failures or installation defects lead to temperature increments in specific points or areas. However, its application to fault detection in electric motors is far less usual. Alternative techniques, based on current or vibration monitoring, are still preferred, despite the analyses of these quantities do not enable the diagnosis of a significant number of failures that occur in these machines. In this regard, infrared data may provide very useful information for the detection of some faults which are not easy to be detected with currents or vibrations. In addition, this can be done in a non-invasive way, i.e., without interfering with the machine operation. The spectacular evolution undergone by the infrared cameras, which even enable the capture of motor thermal transients, represented by sequences of high resolution images as well as the monitoring of the temperature evolution at any point of the surface, is a fact that contributes to the great potential of this technique.In this work, a new methodology relying on the combination between the heat transfer theory and infrared data is proposed. The main pursued objectives are: (1) to study the thermal behaviour and perform the energy balance by building a thermal model of the induction motor using infrared data and (2) to set the baseline for further complex failure diagnosis in electric motors.To achieve these goals, a 1.1 kW induction motor is tested; thermography images of the motor frame are captured every second during the whole startup transient, from standstill till steady-state, by using an infrared camera connected to a laptop computer fitted with an acquisition and analysis software. These infrared data are used in a first stage to build the thermal model of the induction motor. Afterwards, in a second stage, the obtained results are compared with those corresponding to faulty machines to study the applicability of thermography data for diagnosis purposes.The results prove the potential of the approach to become a powerful diagnosis tool, complementing the information provided by techniques relying on other quantities, in cases in which they are not conclusive.     

Scheduling semiconductor in-line steppers in new product/process introduction scenarios

This paper presents a scheduling method for an in-line stepper operating in a new process/production introduction (NPI) scenario. An in-line stepper is a bottleneck machine in a semiconductor fab. Its interior is comprised of a series of chambers, while its exterior is a dock equipped with a limited number of ports. The transportation unit for each chamber is a piece of wafer, while that for each port is a job that can contain up to 25 wafers. This transportation incompatibility may lead to an unexpected capacity loss for an in-line stepper–in particular in an NPI scenario that, by nature, includes a substantial number of small-sized jobs. Such a capacity loss can be alleviated by effective scheduling. A genetic algorithm (GA) scheduling method is proposed to enhance the productivity of in-line steppers. Four other sequencing methods are compared with the GA method. Numeric experiments indicate that the GA method outperforms the four benchmarks. The higher the percentage of small-sized jobs, the better the performance of the GA.     

Wavelength control of tunable dense wavelength-division multiplexing sources by use of a Fabry-Perot etalon and a semiconductor optoelectronic diode

A high-resolution tunable-wavelength controller is achieved by use of an etalon for control of wavelength drift and a semiconductor optical diode (SOD) for channel recognition. The etalon provides a stable wavelength reference, and the SOD can detect mode-hopping and incomplete-tuning problems in tuning a laser. With the help of a Fabry-Perot etalon as a precise wavelength reference, the usual concern with the temperature stability of a SOD can be relaxed at least tenfold compared with wavelength control with a single SOD. We demonstrate the feasibility of monitoring tunable lasers by using a Fabry-Perot laser diode (FPLD) or a semiconductor optical amplifier (SOA). The induced voltage of the FPLD and that of the SOA are modeled with analytic expressions that can help to optimize the operation of a SOD sensor.     

Tunable single frequency thulium:YAG microchip laser with external feedback

By use of the reflection of an uncoated external etalon, a diode-pumped thulium-doped YAG microchip laser was forced into a single-frequency mode. The wavelength of the single-frequency radiation was tunable over 15 nm simply by translation of the etalon relative to the laser. Output powers of 45 mW were achieved in a monolithic setup that is insensitive to vibrations. The origin of the single-frequency oscillation is the wavelength-dependent reflection of the etalon, which is coupled back into the laser resonator. This method permits the combination of inherently stable, single-frequency resonator geometries such as microchips with laser materials that have broad tuning ranges.