Estimation of induction machine inverse rotor time constant using torque angle tangent calculation

A new inverse rotor time constant estimation scheme for an induction machine is presented. For high performance induction machine control, indirect rotor flux oriented vector control is the most commonly applied control technique. It requires that an accurate estimate of the inverse rotor time constant is obtained to ensure correct orientation of the current vector with the rotor flux vector. An incorrect estimate will result in an incorrect flux level, reduced dynamic torque performance and reduced maximum available torque. A novel parameter estimation scheme is presented, based on the calculation of the tangent of the torque angle. The effectiveness of the technique is demonstrated through simulation and practical results.     

Limitation of the load angle in a direct-torque-controlled synchronous machine drive

The basic direct torque control (DTC) principle is to rotate the flux linkage forward, if the torque must be increased, and reverse, if the torque must be decreased. The torque is, however, increased only up to a maximum torque of the machine, which corresponds to a load angle of about 90/spl deg/ in a synchronous machine. This paper presents a method to overcome the possible loss of synchronism when using DTC. This requires either that the rotor angle is measured or estimated. Both of these cases are considered. Simulation and laboratory results are presented to show the effectiveness of the presented method.     

On-line fuzzy tuning of indirect field-oriented induction machinedrives

This paper presents an on-line fuzzy tuning scheme for indirect field-orientation (IFO)-controlled induction machine drives. A fuzzy controller is used to regulate the speed, and another two fuzzy compensators are combined to correct detuning of field orientation. Since detuning effects of the IFO induction machine drive is minimized by the new fuzzy control scheme, the induction machine can achieve good performance in terms of overshoot, steady-state error, torque disturbance, and variable-speed tracking. Efficiency and torque/ampere capability are also enhanced. The results obtained by laboratory implementation are presented to verify the effectiveness of the proposed on-line fuzzy-tuning scheme     

Direct self control with minimum torque ripple and high dynamics for a double three-level GTO inverter drive

A highly dynamic control scheme with very low torque ripple-direct self control (DSC) with torque hysteresis control-for very high-power medium-voltage induction motor drives fed by a double three-level inverter (D3LI) is presented. In this arrangement, two three-level inverters that are connected in parallel at their DC sides are feeding the open motor windings. The DSC, well known from two- and three-level inverters, is adapted to the D3LI and optimized for a minimum torque ripple. An 18-corner trajectory is chosen for the stator flux of the induction machine since it is approaching the ideal circle much better than the hexagon known from DSC for two-level inverters, without any detriment to the torque ripple. The machine and inverter control are explained and the proposed torque quality and dynamics are verified by measurements on a 180-kW laboratory drive.     

采用光电方式测量转轴扭矩的原理研究

本文介绍了激光读出头的工作原理.提出了一种采用激光读出头、运用光电方式对转轴扭矩进行测量的原理.通过间接测量转轴的扭转角,从而得到转轴的扭矩值.既能进行静态测量,又能进行动态测量,使扭矩的测量得到进一步的完善.     

High-performance adaptive robust control with balanced torque allocation for the over-actuated cutter-head driving system in tunnel boring machine

The tunnel boring machine(TBM) is a kind of large-scale underground equipment for the tunnel and subway excavations. The cutter-head driving system is one of the key components in hard rock TBM, which is driven by multiple motors to provide enough torque during the excavation. Synchronizing motions of the multiple driving motors and balancing the driving torques are two essential control issues to be addressed of cutter-head driving system. However, the existing synchronization control approaches usually focus on the pure motion synchronization of the multiple driving motors only. These methods will lead to the phenomena of uneven driving torques even when their motions are quite well synchronized, and may result in the shaft broken accident. Instead in this paper, an adaptive robust control law integrated with torque allocation technique scheme is proposed that achieves not only better motion synchronization of the driving motors but also simultaneous regulation of driving torques. Namely, the adaptive robust control (ARC) is introduced to deal with the negative effects from uncertainties and variable load acting on the cutter-head. And a torque allocation algorithm is proposed to distribute the driving torque of each motor evenly. Comparative simulations are carried out to verify the excellent performance of the proposed scheme.     

Optoelectronic transfer of information from a rotating shaft

The letter describes a scheme which enables signals to be transferred from a rotating shaft via an optical link, and without the need for rubbing contacts. Consideration is given to the geometry of the link when the shaft ends are either accessible or inaccessible. Experimental results are presented for a typical scheme used to provide a record of the torque transmitted by a shaft.     

Voltage control strategy for maximum torque operation of aninduction machine in the field-weakening region

In this paper, a novel field-weakening scheme for the induction machine is presented. The proposed algorithm, based on the voltage control strategy, ensures the maximum torque operation over the entire field-weakening region without using the machine parameters. Also, by introducing the direct field-oriented (DFO) control, which is insensitive to the variation of machine parameters in the field-weakening region, the drive system can obtain robustness to parameter variations. Moreover, the speed sensorless control can be achieved in the very-high-speed range, where the utilization of the speed sensor is limited. Experimental results for the laboratory induction motor drive system confirm the validity of the proposed control algorithm     

Torsional Vibration Assessment Using Induction Machine Electromagnetic Torque Estimation

Mechanical anomalies such as load troubles, great torque dynamic variations, and torsional oscillations result in the shaft fatigue of electrical machine and other mechanical parts such as bearings and gearboxes. Particularly, the torsional vibration may attain a significant level at resonant frequencies which damage or cause additional lifetime consumption of mechanical parts. In this way, this paper proposes a noninvasive technique through the electromagnetic torque estimation of driving induction machine as a mean of mechanical torsional stresses monitoring. The lubrication loss is considered as a gear failure to demonstrate its influence on the vibration and on the electromagnetic estimated torque signatures. Then, it is shown that the information in the electromagnetic torque can be decomposed into high- and low-frequency bandwidths which are associated to induction machine and gearbox mechanical-related frequencies, respectively. A setup based on a 5.5-kW three-phase squirrel-cage induction motor connected to a 4-kW wound-rotor induction generator via a one-stage gearbox has been used to validate the proposed method in both stationary and nonstationary conditions.     

Theoretical and Experimental Reevaluation of Synchronous Reluctance Machine

This paper theoretically introduces and develops a new operation diagram (OPD) and parameter estimator for the synchronous reluctance machine (SynRM). The OPD demonstrates the behavior of the machine's main performance parameters, such as torque, current, voltage, frequency, flux, power factor (PF), and current angle, all in one graph. This diagram can easily be used to describe different control strategies, possible operating conditions, both below- and above-rated speeds, etc. The saturation effect is also discussed with this diagram by finite-element-method calculations. A prototype high-performance SynRM is designed for experimental studies, and then, both machines' [corresponding induction machine (IM)] performances at similar loading and operation conditions are tested, measured, and compared to demonstrate the potential of SynRM. The laboratory measurements (on a standard 15-kW Eff1 IM and its counterpart SynRM) show that SynRM has higher efficiency, torque density, and inverter rating and lower rotor temperature and PF in comparison to IM at the same winding-temperature-rise condition. The measurements show that the torque capability of SynRM closely follows that of IM.     

浅谈螺杆钻具传动轴的结构分析与改进设计

螺杆钻具中最为关键的部件便是传动轴,文章中利用有限元技术分析了传动轴在扭矩状态下的应力、变形状态,指出了其存在的危险部位,且在结合实际生产需求的基础上,提出了相应的改进方案,得到了随结构参数变化的应力及变形曲线,为传动轴的设计提供了更多的参考依据.     

Dynamic and Vibration Analysis of a Multimotor DC Drive System With Elastic Shafts Driving a Tissue Paper Machine

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four DC motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system.     

Low-speed sensorless control of induction Machine

Induction motor (IM) speed sensorless control, allowing operation at low and zero speed, optimizing torque response and efficiency, will be presented in this paper. The magnitude and the orientation angle of the rotor flux of the IM are determined by the output of the closed-loop rotor-flux observer based on the calculation of the extended electromotive force of the machine. The proposed rotor-flux-oriented control scheme is robust to parameter variations and external disturbances. Both observer and controller utilize the continuous sliding mode and Lyapunov theory. A smooth transition into the field-weakening region and the full utilization of the inverter current and voltage capability are thus possible. The produced torque is a continuous output variable of control. The performance of the proposed method is investigated and verified experimentally on a digital signal processor.     

高压变频调速系统在黑河欧林煤矿输煤皮带机上的应用

输煤皮带机是广泛应用于煤矿斜井的运输设备,本文采用具有转矩自适应功能高压变频器作为鼠笼式异步电动机的受控电源,既能保证低速启动转矩大于负载转矩,又可以实现无级调速,满足工艺要求,当工况无需满负荷运转时又可以节约电能。     

VT710多电机高压驱动在煤矿主井皮带运输机上的应用

主井皮带机是煤矿的中枢,一旦皮带机出了故障,将造成全矿停产。原有系统采用交流绕线式电机串电阻调速系统。电动机效率低,损耗大。整个系统效率低,调速范围有限,稳定性差。采用VT710高压变频器的转矩自动平衡控制模式,以达到理想的同步控制效果。     

A Direct-Flux-Vector-Controlled Induction Generator With Space-Vector Modulation for Integrated Starter Alternator

A direct-flux-vector-controlled scheme of induction generator has been proposed in this paper for future 42-V automobile application. The fundamental relationship between the rotating speed of the stator flux vector and torque is analyzed. A simple structure with only one proportional-integral (PI) controller is shown to implement the torque and flux controls adequately. By controlling the electromagnetic torque of the induction machine, the required dc-bus voltage can be well regulated within the 42-V PowerNet specifications. Fixed switching frequency and low torque ripple are obtained with space-vector modulation technique. Simulation and experimental results indicate that the proposed scheme provides a practical solution for an integrated starter alternator other than the widely applied field-oriented- control scheme.     

DTC Drives for Wide Speed Range Applications Using a Robust Flux-Weakening Algorithm

A control scheme for robust flux-weakening operation of direct-torque-control induction motor drive is proposed. The basic idea is to adjust the flux reference on the basis of the torque error, thus determining a spontaneous flux weakening. To exploit the maximum torque capability, it is necessary to estimate the maximum torque that the induction machine is able to generate at any speed. Initially, a basic version of the algorithm, requiring a simple off-line parameter tuning, is presented. Then, the algorithm is improved and completed with the online estimation of the maximum torque, hence avoiding the initial tuning process. The main features of the proposed methods are a little dependence on machine parameters and a smooth transition into and out of the flux-weakening operation mode. Experimental tests demonstrate the effectiveness of the control schemes.     

Erkennung defekter Rotorstäbe an umrichter- und netzgespeisten Asynchronmaschinen durch die Vienna Monitoring Method

The introduced paper deals with faulty rotor bars in the squirrel cage of an induction machine including the detection by means of the Vienna Monitoring Method. Electrical asymmetries in the rotor cage lead to thermal stress of the rotor and to additional modulations of shaft torque. Furthermore additional harmonic components in the currents (and voltages) occur. The fault related torque modulations can be seized by means of models and are reliably detectable by the Vienna Monitoring Method. This robust monitoring technique is therefore suitable for grid supplied machines and for inverter drives.     

A Current Source Inverter Fed Induction Motor Drive with Power Factor Angle Control Using Microprocessor

This paper describes a method of adjusting the stator power factor angle for the control of an induction motor fed from a current source inverter (CSI) based on the concept of space vectors (or park vectors). It is shown that under steady state, if the torque angle is kept constant over the entire operating range, it has the advantage of keeping the slip frequency constant. This can be utilized to dispose of the speed feedback and simplify the control scheme for the drive, such that the stator voltage integral zero crossings alone can be used as a feedback for deciding the triggering instants of the CSI thyristors under stable operation of the system. A closed-loop control strategy is developed for the drive based on this principle, using a microprocessor-based control system and is implemented on a laboratory prototype CSI fed induction motor drive.     

Independent Control of Average Torque and Radial Force in Bearingless Switched-Reluctance Motors With Hybrid Excitations

Radial force and torque are the control objectives that determine the machine performance of levitation and rotation in a bearingless switched reluctance motor (BSRM). This paper proposes a control scheme for rotating and levitating a 12/8 BSRM. The motor average torque and radial force are independently controlled with hybrid excitations in main windings and levitation windings. First, the mathematical relationship between radial force and currents, which is utilized in this paper, is derived by using the Maxwell stress tensor method. Then, the proposed control scheme is analyzed. The average torque of each phase generated in the levitation region equals zero for its symmetry of the aligned position. Accordingly, the current calculating algorithm is deduced to minimize the magnitude of instantaneous torque in the levitation region. The principle and realization of the proposed scheme are demonstrated with finite-element (FE) analysis. Experimental results show that the proposed scheme is effective for a stable levitation.