Optimization of Three-Phase Induction Motor Design Part II: The Efficiency and Cost of an Optimal Design

With the continuing increase of the cost of electrical energy, motor manufacturers and consumers became increasingly concerned with the energy conservation available from highly efficient electrical motors. Motor cost and efficiency are interrelated; therefore, the effect of motor cost on the maximum obtainable efficiency is of interest both to the motor manufacturer and to the consumer. The relation between the power factor and the maximum efficiency of a motor is another aspect of energy conservation. The optimal motor design, with respect to the maximum efficiency, and with respect to the minimum motor cost (by means of a mathematical optimization method described in Part I), was used in Part II to investigate the above-mentioned motor relations. Three motor-cost functions were investigated: production cost, capitalized cost, and annual cost. The motor that was used in the study was a 100 hp, three-phase, squirrel-cage induction motor.     

感应电动机随动功率因数法节电控制的研究

本文充分考虑了目前国内外感应电动机的节电原理，确定以随动功率因数法作为实现节电的手段；同时介绍了一种自动节能控制装置。     

Behavior of the Three-Phase Induction Motor With Spiral Sheet Rotor

Improvements in torque at low currents using a rotor with spiral sheets are analyzed. Several rotors and stators have been built combining different constructive and mechanical characteristics of the related elements: inertias, constructive materials, geometrical shapes of the sheets, and geometrical disposition of the sheets. These different types of motors have been simulated using computer-aided tools and then tested in the laboratory. Finally, four stators (1000, 1500, 1500-type A, and 3000 r/min), with the same constructive parameters, have been simulated and tested with the following rotors types: solid rotor, solid rotor with diamagnetic rings, drag cup, and simple and double squirrel cage rotor; the results have been compared to those obtained with the seven variants of the spiral sheet rotor presented in this paper.      

Optimal Efficiency Control of an Induction Motor Drive

This paper describes a practical method for achieving optimal efficiency over the complete operating range of a variable speed drive. The proposed system adaptively adjusts the flux level in the motor based upon a direct measurement of the power input to the drive. An internal field orientation torque control loop and a speed regulator are employed to maintain the load speed requirements. Experimental results describing the efficiency optimization and the dynamic behavior of the drive at reduced flux are presented. The influence of the tuning of the field oriented controller on the efficiency of the drive is experimentally investigated.     

A Complete Time Domain Model of the Induction Motor for Efficiency Evaluation

The saturation of mutual and leakage inductances as well as the eddy currents effects are taken into account to represent an almost complete model of the induction motor. These effects are not trivial, when the stator voltage and/or frequency changes considerably. Therefore, the model is suitable for the motor performance studies under nonsinusoidal voltage waveform supplies. The effects of eddy currents are represented by a simple double cage model equivalent to the deep bar cage. A practical method for finding the double cage parameters is outlined and the results obtained were used in the simulation. The accuracy of the model is emphasized by comparing the simulation results with test results of the stator inrush current during starting under no-load conditions. The model is used for calculating the induction motor losses in the time domain, when the motor is fed from nonsinusoidal voltage waveform supplies. Samples of the obtained results from different voltage waveforms are given together with that of a pure sinusoidal voltage supply for comparison.     

Capacitors Required for Maximum Power of a Self-Excited Single-Phase Induction Generator Using a Three-Phase Machine

This paper aims to determine the optimal capacitors required for maximum output power of a single-phase self-excited induction generator (SEIG), using a three-phase machine feeding inductive as well as capacitive loads. The generator consists of a three-phase star-connected induction machine with three capacitors and a single-phase load. The algorithm, which gives directly the values of the optimal capacitors for the maximum power output and the maximum power available, has been developed using the steady-state model of the SEIG and sequential unconstrained minimization technique (SUMT). The variations of the maximum power output with power factor (pf) of loads (both inductive and capacitive) and speed of the SEIG have been presented. The voltage regulation of the generator is small due to the effect of the two series capacitors. Experimental results have shown the effectiveness and accuracy of the developed algorithm.     

Novel Circuit Configuration for Compensating for the Reactive Power of Induction Generator

A novel circuit configuration for compensating for the reactive power of an induction generator is proposed in this paper. This reactive power compensator includes an ac power capacitor set serially connected to a small-capacity power converter. The ac power capacitor is adapted to provide basic reactive power and reduce the voltage rating and power capacity of the power converter. Because, the ac power capacitor set can also effectively block the dc voltage generated by the power converter to the utility, the salient point of the proposed reactive power compensator is that only a two-arm structure is required for the power converter in the three-phase three-wire application. Consequently, the required number of power electronic switches for the power converter is reduced. The current, generated by the induction generator system, supplied back to the utility is sinusoidal and in phase with the utility voltage following compensation of the proposed reactive power compensator. A prototype is developed and tested to verify the performance of the proposed reactive power compensator. The experimental results show that the performance of the proposed reactive power compensator is as expected.     

提高感应加热电源加热效率的一种方法

提出了在中频感应加热电源整流控制电路中采用功率，电压双闭环控制策略，实现感应加热过程的恒功率调节，可有效地提高感应加热电源的加热效率。     

Simple Power Control for Sensorless Induction Motor Drives Fed by a Matrix Converter

This paper presents a new and simple method for sensorless control of matrix converter drives using a power flowing to the motor. The proposed control algorithm is based on controlling the instantaneous real and imaginary powers into the induction motor. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-on and turn- off times of switching devices, and on -state switching device voltage drop are modeled using a PQ power transformation and compensated using a reference power control scheme. The proposed sensorless control method is applied for the induction motor drive using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.      

三相异步电机定子功率因素与转子功率因素分析

分析了三相异步电机功率因素以及异步电机不同运行状态时的功率因素,得出,转子绕组功率因素与定子绕组功率因素在异步电机不同运行状态,是有差异的。     

Influence of Insulation Level on Electric Power Quality and Transformation Efficiency of Grid-Connected Photovoltaic Power Plants

The paper considers the influence of the insolation level on the electric power quality indicators and efficiency of a grid-tie inverter operating as part of a grid-connected photovoltaic power plant. Over the course of a year, data were recorded for Moscow on incoming solar radiation and the grid-tie inverter input and output capacity provided by a 1 kW grid-connected photovoltaic power plant. The insolation threshold values for a Solar River 1100 TL inverter are experimentally established, corresponding to both the beginning and end of stable inverter operation, as well as the required phase angle value for the electric energy supplied to the grid.     

局部电网三相不平衡畸变电流补偿方法

在三相三线制局部低压配电网中,易出现电流畸变和三相不平衡情况,对设备运行及配电网安全造成不利影响。在采用有源电力滤波器（APF）进行谐波与三相不平衡综合补偿时,因传统[ip-iq]法无法有效消除二倍频分量,故补偿效果不甚理想。该文基于传统[ip-iq]方法提出了一种改进[ip-iq]法,得出了低通滤波器参数与APF补偿电流的定量关系,并据此进行了APF主要参数的设计。仿真与实验结果证明采用改进[ip-iq]法时,谐波与不平衡补偿的效果与低通滤波器的截止频率无关,保持了良好的稳定性,且提高了系统的响应速度。     

DFIG三相四开关网侧变流器预测功率控制策略

针对双馈感应发电机（DFIG）网侧变流器（GSC）采用三相四开关拓扑时的运行控制问题,设计了一种新型预测功率控制器。新型控制方案中采用了三个电压矢量来确保GSC开关频率保持恒定,同时使GSC有功和无功功率纹波最小化。同时,控制器可计算出补偿功率以消除直流侧中点电位波动,无需使用低通滤波器。利用DFIG测试平台开展了实验,结果表明新型预测控制能有效抑制直流母线电压失衡,并具有快速动态响应特性,且GSC电流总谐波失真较低。     

电机降压节电技术--Powerking电机节电器

介绍了对异步电动机降压节电技术和Powerking电机节电器的节电原理及保护功能。     

交流变频调速系统效率优化方法

在交流电机变频调速技术应用日益广泛的情况下,变频装置效率优化就显得极为重要,选择一种合适的优化方法来改进系统效率也成为电力传动的研究课题之一。浅析了三种优化方法,提出了应用建议。     

不可逆Dual循环的功率效率特性

用有限时间热力学的方法考虑空气标准 Dual循环 ,导出了存在摩擦及传热损失的空气标准 Dual循环的功率与压缩比、效率与压缩比以及功率和效率的最佳特性关系 ,同时由数值计算分析了摩擦和传热对循环性能的影响特点。     

火力发电厂效率计算及联合循环发电的优势

论述了火力发电厂的效率计算。数据表明,采用燃气－蒸汽联合循环发电技术的温州燃机电厂效率高,并对此作了经济指标对比。     

二次再热汽轮机能级效率法研究

在一次再热汽轮机能级效率法的基础上推导出二次再热机组能级效率法的计算公式,并针对某1 000MW二次再热项目对推导的计算公式进行验证。在计算的过程中,分别对THA、TMCR、VWO、75%THA、50%THA这5个工况进行能损分析计算,获得了各工况下热力系统主循环的能级效率及辅汽能损值。采用能级效率法计算的热耗与实际计算热耗一致,验证了二次再热能级效率法计算公式的准确性。这也为能级效率法向更加复杂的热力系统的应用推广提供了思路。     

VVVF变频器的功率因数

介绍了VVVF变频器的功率的概念和形成原因，分析了整流方式对变频器功率因数的影响及PAM，PWM整流方式的功率因数特征，电压、电流型变频器和PWM变频器负荷率与功率因数的关系。     

考虑摩擦时Otto循环功率效率特性新析

对有摩擦时的 Otto循环进行了有限时间热力学分析。建立了一种新的模型 ,以循环的活塞平均速度和摩擦系数为基准求得了摩擦损失功率以及功率和压缩比、效率和压缩比的关系 ,进而得到了功率与效率关系 ,并进行了计算和讨论。结果表明 ,与实际热机循环的性能特性一致。