Decoupled control of rotor torque and rotor electric power delivered in a salient-pole, synchronous machine

A drive system with a control algorithm that provides independent control of rotor torque and rotor electric power is described in this paper. One electromechanical machine is used for two purposes, viz., firstly to provide electromagnetic torque to rotate a rotor mounted load and secondly to provide electric power to equipment mounted on the rotor. The technique eliminates the need for slip rings. Simulation and practical results verifying the analysis are given. The system has applications such as rotational antennas and turret systems.     

Neural network based modeling of round rotor synchronous generatorrotor body parameters from operating data

It is generally accepted that in order to account for the effect of eddy currents in the solid rotor-iron of a round-rotor synchronous machine, two or more fictitious rotor-circuits are to be used in each axis of the d- and q-axis equivalent circuit representations of the machine model. This paper presents a novel technique to estimate the parameters of these rotor-circuits (hereinafter referred to as rotor body parameters) from measurements collected online at several operating conditions. The effects of generator saturation, rotor position and loading are included in the estimation process. Tests conducted on a round-rotor synchronous generator reveal that certain rotor-body parameters are nonlinear functions of generator operating condition. A novel artificial neural network (ANN) based technique is used to map variables representative of generator operating condition to each parameter being modeled. The developed ANN models are validated with measurements not used in the modeling process     

Synchronous Machine steady-State parameter estimation using neural networks

An online steady-state parameter estimation technique using the ability of the neural networks to recognize patterns is presented in this paper. The method is nonintrusive. Studies on a salient pole and on a round rotor synchronous machine illustrate the effectiveness of the proposed technique. Results indicate that the steady-state parameters can be obtained without the use of rotor position.     

Analysis of a Permanent Magnet Synchronous Machine Supplied from a 180° Inverter with Phase Control

Reference frame theory is used to establish the equations which describe the steady-state and dynamic behavior of an electric drive system consisting of a permanent magnet synchronous machine supplied from an inverter operating in the 180° conduction mode and with provisions to shift the phase of the stator voltages relative to the rotor position. An expression for the phase-shift angle which yields maximum torque is derived. It is shown that a comparison of the stator time constant and the no-load rotor speed without phase shift, can be used to anticipate the increase in average torque achievable by phase shifting. It is also shown that advancing the phase of the stator voltages advances the phase of the fundamental component of the stator phase currents relative to the phase voltages. A method of calculating the steady-state harmonic currents and torque is also given. The information given in this paper should serve as a guide for the operation of brushless dc motors and the design of speed or position controls that employ phase shifting techniques along with or instead of pulse width modulation.     

同步电机转子初始位置测量方法

为使电机顺利起动,并获得最大的起动转矩,需要测量同步电机的转子初始位置,以确定合适的起动电压。在分析电机感应电动势的基础上,通过坐标变换推导出同步电机的转子初始位置计算方法,并通过仿真和试验验证了该方法的可行性。     

Dynamic study of an electronically brushless DC machine viacomputer simulations

The authors analyze a machine with a conventional DC armature winding on the stator which does not have a field winding connected with slip rings. At positions where the winding would have been attached to a commutator segment, a transistor switch is attached instead. The rotor contains a permanent magnet field. The lap wound stator winding is sequentially commutated by a system consisting of a position sensor and logic circuitry. Analytical expressions for a full pitch lap wound machine are given. A computer simulation of the machine was implemented. The results serve to illustrate the considerations which must be made in the design of this type of machine, in particular the effects of the winding design on commutation and cost efficiency     

某60Hz、185MW汽轮机转子高速动平衡试验试重大小及位置探究

针对汽轮机转子个性化设计的特点,文章结合在250t试验台位上进行转子高速动平衡试验所积累的经验。对全新设计的某60Hz、185MW汽轮机转子厂内动平衡试验平衡块试加重量及方位角进行探究。实践证明．文章总结的方法可以有效地缩短转子动平衡时间,并可以推广应用到其它转子厂内高速动平衡试验上。     

Slotless permanent magnet synchronous motor operation without ahigh resolution rotor angle sensor

An implementation for sinusoidal current control of a slotless permanent magnet synchronous motor (PMSM) with discrete Hall sensor position feedback is presented. To estimate the rotor position of the slotless PMSM, a flux estimation technique is used that takes advantage of the slotless machine's characteristically low inductance to limit flux estimation error. The rotor position is estimated using a reference model and the measured phase currents and voltages. At startup and very low speeds, discrete Hall sensors are used to limit the position estimation error to approximately ±30 electrical degrees and to prevent the flux estimators from drifting due to measurement noise and offset. The proposed sinusoidal control method reduces the torque pulsations present when Hall sensor position feedback alone is used and eliminates the need for high-resolution rotor angle sensors. The proposed control strategy is applied to a slotless PMSM drive system and implemented using a digital signal processor (DSP). Experiments are carried out for the system and the results demonstrate the effectiveness of the control     

旋转机械的自组织映射神经网络故障分类方法研究

旋转机械广泛应用于工业生产中,对旋转机械的故障诊断方法很多,本文根据自组织映射神经网络原理,应用故障诊断的标准样本进行神经网络的训练,并通过实验的方法给出自组织映射神经网络对故障分类的方法。     

Determination of damper winding and rotor iron currents inconvertor- and line-fed synchronous machines

The damper winding currents of a synchronous machine with a solid iron rotor are analyzed. Based on the self and mutual inductance modelling technique, the damper currents are described by a detailed damper model taking the damper cage and the rotor iron into account. The model's component elements are determined by the finite element method. Theoretical results are verified by measuring damper bar currents of a six-phase synchronous machine fed by two six-pulse converters. For a number of different operating modes the model is used to calculate the damper current distribution of a six-phase machine     

Effect of excitation capacitors on transient performance ofreluctance generators

The transient responses of a reluctance generator connected to an infinite power system excited by a bank of terminal capacitances are compared to those when load excitation is used. A mathematical model is developed to simulate the machine with its terminal capacitor. With the aid of a least-square-error method, this model is used to optimize the machine parameters. The capacitance excitation requirements for different load conditions are then computed using a steady-state model. The comparison of the transient responses shows that the terminal-capacitor excitation method has several advantages over the load excitation method. It reduces the first rotor swing and gives more damping to the subsequent rotor oscillations. It also increases the critical fault-clearing time and hence the transient stability limits. In addition, it suppresses all power frequency torque oscillations, which are quite pronounced when load excitation is used     

Asynchronous Machine Rotor Fault Diagnosis Technique Using Complex Wavelets

This paper introduces a novel approach for the detection of rotor faults in asynchronous machines, based on wavelet analysis of the stator phase current. To be more specific, the measured stator phase current is filtered through a complex wavelet. Theoretical analysis validates that the spectrum of the modulus of the result of the filtering is free from the fundamental supply frequency component, and the fault characteristics can be highlighted. This is advantageous, especially if the induction machine operates at low slip values, where the characteristic frequency components of the rotor fault are very close to the fundamental frequency component. At the same time, by matching the wavelet function to the frequencies of the faulty components, a narrow bandpass filter at the frequency region of the fault characteristic spectral components is obtained. Furthermore, in the context of this paper, features extracted using the proposed technique are used as input to a support vector machine classifier that is employed for the detection of the rotor fault. Simulation and experimental results demonstrate the effectiveness of the proposed technique.     

Transient thermal characteristics of induction machine rotor cage

Thermal analysis of an induction machine cage rotor during stall conditions forms an important part of design calculations. The study of rotor circuit thermal behavior is also useful to identify causes of failure in large cage rotor induction machines. The authors present a three-dimensional finite-element-based electrical-thermal analysis of the bar and end-ring area of a large rotor to examine its thermal characteristics during a stall. Details of temperature variations at key locations in the bar and end ring are provided. The calculations are compared to experimental results, and the advantages and limitations of the solution technique for rotor analysis are discussed     

Analysis and optimization of an interference fitted composite material rotor of a superconducting energy storage flywheel

为了提高储能飞轮的储能密度,设计了一种金属轮毂和3个复合材料圆环过盈装配的磁悬浮外转子飞轮;采用平面应力方法建立了转子的应力模型,以复合材料圆环的厚度和环间过盈量为优化变量,以储能量为优化目标,在强度约束条件下,通过序列二次规划法对转子进行优化设计,将转子的极限转速从50000 r/min提高到57797 r/min,储能密度由40 W∙h/kg升高到53.8 W∙h/kg,储能量升高34.5%.该研究方法和结果可以为复合材料储能飞轮的设计,制造和优化提供依据.     

Analysis of a single-phase induction machine with a shiftedauxiliary winding

This paper extents the method of multiple reference frames to the analysis of asymmetrical induction motors with nonorthogonal stator windings, with particular emphasis on the permanent split capacitor (PSC) machine. The predictions of the method are verified by comparison to both experimental results and to results obtained using a machine variable computer simulation. Once verified, the method is used to derive the transfer function relating rotor speed to load torque disturbance, which is of particular interest when analyzing PSC machines driving compressor loads. It is shown that the transfer function exhibits a distinct resonant point, and that the magnitude of the resonant peak increases as the motor approaches synchronous speed. It is also shown that the magnitude of the resonant peak may be lowered by increasing rotational inertia or rotor resistance     

Dynamic simulation of dynamic eccentricity in inductionmachines-finding function approach

The paper describes a method for the dynamic simulation of dynamic rotor eccentricity in squirrel cage rotor induction machines. The method is based on a winding function approach, which allows for all harmonics of magnetomotive force to be taken into account. It is demonstrated how this complex dynamic regime can be modeled using the mutual inductance curves of symmetrical machine using proper scaling techniques. Experimental results demonstrate the effectiveness of the proposed technique and validate the theoretical analysis     

Effectiveness of active noise and vibration cancellation for switched reluctance machines operating under alternative control strategies

The effectiveness of active vibration cancellation by inducing antiphase vibration of the stator to reduce the acoustic noise emitted from a switched reluctance machine is evaluated under typical operating modes, viz., single pulse excitation, pulsewidth modulation (PWM) voltage control, and PWM current control. Measurements in both the frequency and time domains are complemented by sound pressure level measurements. It is shown that active vibration cancellation is most effective in reducing a single mode of vibration when a switched reluctance (SR) machine is operated under single-pulse excitation, and becomes less effective when more than one dominant vibration mode exists within the audible frequency range. In general, it also works relatively well when the machine is operated under fixed frequency PWM voltage control, although less effectively than for single pulse control. Further, it is shown that the technique is ineffective when the machine is operated under PWM current control since the duration of the zero voltage period varies significantly from the optimal value due to the random nature of the PWM.     

Extraction of airfoil data using PIV and pressure measurements

A newly developed technique for determining the angle of attack (AOA) on a rotating blade is used to extract AOAs and airfoil data from measurements obtained during the MEXICO (Model rotor EXperiments in COntrolled conditions) rotor experiment. Detailed surface pressure and Particle Image Velocimetry (PIV) flow fields at different rotor azimuth positions are examined for determining sectional airfoil data. The AOA is derived locally by determining the local circulation on the blade from pressure data and subtracting the induction of the bound circulation from the local velocity. The derived airfoil data are compared to 2D data from wind tunnel experiments and XFOIL computations. The comparison suggests that the rotor is subject to severe 3D effects originating from the geometry of the rotor, and explains why the Blade Element Momentum technique with 2D airfoil data over‐predicts the loading of the rotor. The extraction technique is verified by employing the derived airfoil characteristics as input to computations using the BEM technique and comparing the calculated axial and tangential forces to the measured data. The comparison also demonstrates that the used technique of determining the AOA is a reliable tool to extract airfoil data from experimental data. Copyright © 2010 John Wiley & Sons, Ltd.     

FEM analysis of inverter-induction motor rotor conduction losses

A direct method to simulate the steady-state stator and rotor currents in an inverter-induction machine of known geometry and winding design is developed, and the FEM (finite element method) analysis of the skin effect problem is used to determine the variation of rotor resistance with rotor current frequency. The rotor conduction loss can be calculated from these two sets of information. The total losses incurred for a particular mode of inverter operation are determined both experimentally and using the analytical procedure developed here. The total calculated loss is only 3.5% greater than the measured amount, which confirms the validity of the theory developed and its computer implementation. Furthermore, experimental and simulation results of the standstill condition with sinusoidal input were also found to be in close agreement. Finally, the proposed procedure yields information on the instantaneous current distribution throughout the machine, which permits the accurate determination of the flux pattern and optimization of the lamination design