TORQUE AND CURRENT STRESS OF A THREE-PHASE INDUCTION MOTOR DUE TO NON-SIMULTANEOUS SWITCH-ON

ABSTRACT

The paper discusses; the ways for affecting the current and torque surges originating due to non-simultaneous switch-on of feeding phases to a 3-phase induction motor. Here, the non-simultaneous switch-on is defined to be that during which at first two phases are switched on (at an instant defined with respect to the time course of voltage) and only then, with some delay, the switch-on of the third phase follows. The paper demonstrates that -when compared to a simultaneous switch-on of all 3 phases- proper control of non-simultaneous switch-on as defined above can reduce both the motor impact stress and the current surges substantially. However, unproper successive switching-on may increase these unwanted phenomena. First, the present contribution brings an analytical solution for current and torque at zero revolutions and then, in the latter part, the influence of the controlled switch-on motor start is discussed.     

同步发电机的动态阻尼力矩分析

根据由李亚普诺夫定理导出的综合阻尼系数的原理，统一定义了同步发电机的动态阻尼力矩系数和动态同步力矩系数。对同步发电机的阻尼力矩产生的机理进行了分析，并指出了使电力系统稳定装置产生阻尼力矩的同时，不致减少动态同步力矩的理论方向。     

SYNCHRONIZING TORQUE MATRICES AND STATIC BIFURCATIONS IN MULTIMACHINE POWER SYSTEMS

Abstract

The synchronizing torque matrices are used to characterize the transition from stability to instability in a multimachine power system. This transition is called a bifurcation. In this paper we concentrate on static bifurcations. Two representaions are used: the clssical and a detailed one. It is shown that steady state instabilty can be identified by checking the signs of the eigenvlues of the synchronizing matrix. This method has the advantage of applicability to any representation classical or detailed. It also provides a more convenient alternative to the identification of instability by the sign of the determinant of the Jacobian as suggested in the Russian literature. The method is checked using two systems: one with five machines and the other with ten.     

SOLID POLE LOSSES IN SYNCHRONOUS MACHINES FED BY NON-SINUSOIDAL CURRENT WAVES

Abstract

Solid pole synchronous machines fed by current inverters are generally subjected to high pole face eddy-current losses. This paper describes a method which uses a conducting layer at the surface of solid salient poles to reduce these losses. For a given stator geometry and a fundamental frequency there may exist an optimal thickness of conducting layer that minimizes the losses. We calculate the losses by a simple analytical method. As a result we are able to define, in the stator geometry plane, a region where the conducting layer is beneficial. Outside this region the conducting layer may be detrimental. The domain's variations are investigated as a function of the fundamental frequency and the material. Parameters.     

考虑转子谐波电流影响后双馈电机电磁功率的分析与计算

有不少文章研究了双馈电机的稳态运行性能，但在研究其性能时考虑谐波电流影响的却较少。该文从该类电机的基本电磁关系出发，提出了基波和谐波的等效电路，给出了谐波电路中参数的计算方法。导出了基波电磁功率、稳定谐波电磁功率及脉动谐波电磁功率的计算公式。文章最后以一个实际的绕线型感应电机用交直交电压型逆变器供给励磁的双馈电机为例，计算了主要谐波的稳定和脉动的电磁功率以及电机总的电磁功率。结果表明，该文给出的分析与计算方法是有效的。     

CALCULATION OF THE LOCKED ROTOR CURRENTS AND TORQUE IN INDUCTION MACHINES

ABSTRACT

The analysis of certain end-winding vibration problems requires an accurate knowledge of the transient currents in an induction motor during the early part of the start-up period where the time rates of change of current are the highest. This paper details the derivation of expressions for the winding currents assuming that the machine remains at rest during the period of interest. Under these conditions, the currents are shown to contain three time dependent components, one of which is oscillatory, the remaining two being damped exponentials. The rates of decay of the exponential components are particularly important to some aspects of the vibration problem and they are shown to be dependent on the winding resistances and inductances and also upon the degree of coupling between stator and rotor.     

COMMUTATION TRANSIENTS IN SELF-CONTROLLED SYNCHRONOUS MACHINES CONNECTED TO D.C. NETWORKS

ABSTRACT

In this paper the commutation phenomenon in a synchronous machine (generator or motor) associated with a thyristor bridge is studied. The transient analysis of the different currents in the different windings is done for a salient pole synchronous machine with damper windings. The different expressions are given in terms of the classical machine reactances and time constants which can be directly measured or furnished by the manufacturer. Comparison between theoretical and practical results are given.     

永磁同步电动机直接转矩控制方法的比较研究

提出一种用于永磁同步电动机的基于磁链误差矢量补偿的直接转矩控制（EFVC—DTC）策略，给出了磁链误差矢量的估计算法，并将该控制策略下的稳态和动态运行性能与常规DTC进行比较。仿真及实验结果表明EFVC—DTC可以使电力开关器件工作在基本固定的频率上，磁链和转矩脉动显著减小，比常规DTC具有更优越的稳态性能，而动态转矩响应几乎与常规DTC相同。     

A MODAL APPROACH TO THE TRANSIENT ANALYSIS OF SYNCHRONOUS MACHINES

ABSTRACT

A novel method for calculating the transient currents, flux linkages and electromagnetic torque of a synchronous machine following a sudden voltage disturbance is presented. The solution is obtained for a sudden change from an arbitrary balanced to an arbitrary unbalanced voltage condition. Since minimum constraints are placed on the disturbance, many typical types of transients such as three-phase and line-to-line short-circuit faults can be accommodated. Complete solutions for all machine currents are obtained as explicit functions of time. Any number of rotor circuits can be included and full allowance is inherently made for coupling between all stator and rotor circuits. Constant speed is assumed but no additional approximations are made other than those implicit in the derivation of Park's Equations. The technique incorporates the state space concept of modal analysis in its implementation. Closed form solutions obtained by the modal theory are compared with standard solution techniques     

机网暂态过程数值仿真中的同步电机模型

提出了一种新的适用于电力系统机网暂态过程数值仿真的无阻尼组同步电机模型,通过采且“先求通解,再用梯形法求积”的方法对同步电机的电压方程组进行差分化,成功地消除了因旋转电势引起的、存在于同步电机直轴电压方程和交轴电压方程之间的耦合,导出了相互解耦的直轴和交轴瞬态等值电路。通过算例比较了该模型与ＥＭＴＰ模型的仿真结果,证明这种新模型是正确的,其仿真算法比ＥＭＴＰ算法更精确、更稳定。     

EFFECT OF SKEWING ON THE COGGING TORQUE IN INDUCTION MACHINES

ABSTRACT

This paper presents a simplified method to predict the cogging torque in induction machines including the skewing effect An equivalent circuit including die effect of both slot harmonics and rotor skewing is developed. A special attention is paid to study the skewing effect on the machine behaviour especially at starting instant. Moreover, the leakage reactance due to the skewing is calculated using the suggested method. Useful conclusions are given at the end of this paper which is thought of good use and valuable for both designers and users of squirrel cage induction motors.     

ANALYSIS AND CONTROL OF TORQUE PULSATIONS IN CURRENT FED INDUCTION MOTOR DRIVES

ABSTRACT

Three types of feedback compensation schemes are described which can be used to reduce the torque pulsations which normally occur when induction machines are supplied from a current source inverter. The approach is verified both by a detailed computer simulation and also by test results from an actual system. Limitations of the method near zero slip frequency (no load) is discussed and a means suggested for elimination of the problem.     

平板导体中裂纹缺陷探伤涡流场的求解

裂纹缺陷是涡流检测中最常遇到的缺陷类型。根据裂纹的特点,可以把它近似为一个没有 度的面缺陷,其作用由分布在裂纹面上的等效电流偶极子层代替。使用积分方程法计算其涡流场问题,只需要很小的计算量。以前的工作都以无限厚导体为求解对象,文中研究了有限厚平板导体,结果表明它更加接近涡流检测的真实情况。线圈阻抗的计算值与实验结果进行了比较,吻合很好。     

INVESTIGATION OF THE ROTOR OVERVOLTAGE IN SYNCHRONOUS MACHINES WITH RECTIFIER EXCITATION

Abstract

Electrical motors and generators used on mobile platforms--including aircraft and ship and land vehicles--are required to exhibit as high a power density as practically possible. With the advent of high-energy permanent magnets, it appears possible to build permanent magnet machines which can compete with electrically excited machines in terms of power density. This paper presents a discussion of the power density limitations as they apply to synchronous-type permanent magnet machines using rare earth cobalt permanent magnets. It also presents guidelines for future material development necessary to improve the power density of this class of machines.     

TORQUE PRODUCTION IN ac MOTORS WITH CONSTANT CURRENT SUPPLY

ABSTRACT

Basic theory is presented concerning the production of torque in synchronous motors and induction motors under conditions of constant current supply. Simple methods are described for treating the effects of magnetic saturation, which are important at high currents. It is shown that, for a given stator current, a synchronous motor produces more torque than an induction motor, albeit with higher air-gap flux. Examples illustrate the variation, due to saturation, of the optimum torque angle of synchronous motors with cylindrical and salient rotors.     

ADDITIONAL LOSSES IN SOLID-ROTOR SALIENT-POLE SYNCHRONOUS MACHINES ASSOCIATED WITH STATIC CONVERTORS

Abstract

In solid-rotor synchronous machines associated with static converters, the harmonics generated by the operation of converters result in additional losses in the different parts of the machine. These losses are investigated in this paper. The rotor harmonic currents are determined, the machine equivalent-circuits are derived, and the losses are obtained for the general case of salient-pole machines. The results show that the additional losses are considerable and that constructing the solid-rotor machines with simple damper cages and laminated pole faces has the most prominent effect on reducing these losses.     

NATURAL COMMUTATION IN SOLID ROTOR SYNCHRONOUS MACHINES ASSOCIATED WITH STATIC CONVERTORS

Abstract

In this paper the natural commutation phenomenon in solid rotor synchronous machines is treated. An analytical approach is used, and the effect of the solid iron parts in the rotor is considered by an approximate method. The decrement time functions of the commutation currents due to the iron body are determined for the general case of salient pole machines. The results show that the rotor eddy currents modify considerably the values of the armature commutation currents and their duration.     

PWM逆变器-感应电机驱动系统中接地电流EMI问题的分析

在IGBTPWM逆变器－感应电机驱动系统中，IGBT的高速开关动作产生很高的dv/dt|和|dt/dt|能够导致严重的电磁干扰（EMI）问题。研究表明不仅需要了解干扰的频谱。而且也必须知道它们的时域波形才能全面刻画干扰的本质。如何准确描述并分析这种问题是复杂而困难的，该文应用系统函数的方法来描述这种EI耦合通道的特征，并不需要对寄生电路进行复杂的参数提取，而且能准确预测了EMI的时域波形和频谱特性，接地电流脉冲峰值对应|dv/dt|的 峰值，导通时，|dv/dt|基本不随着负载电流的变化而变化，而关断时，负载电流越小，|dv/dt|越小，由于|dv/dt|在开通时的值要比关断时大得多，因此接地电流EMI问题主要由IGBT的开通决定。系统函数的幅度频谱呈现带通特性，尽管逆变器工作时其拓扑结构发生变化，但是对描述耦合通道的系统函数的影响很小，当三相桥臂的两个IGBT同时开通或同时关断时，接地电流加倍。     

EXACT RELATIONSHIPS BETWEEN PARAMETERS AND TEST DATA FOR MODELS OF SYNCHRONOUS MACHINES

ABSTRACT

In a recent paper the authors have presented a new method expressing the parameters of a synchronous machine model in terms of measurable time constants, without the traditional simplifying assumptions. The considered model is characterized by equal mutual reactances between armature, field and damper windings.

This paper shows the extention of the new method to the models with all three unequal mutuals and with two equal mutuals. The exact relationships between the parameters of the examined models and the test data are provided. Comparisons are made between new and old method results to demonstrate the discrepancies in values of parameters.     

永磁同步电机控制系统中变比例系数转矩调节器设计研究

针对转矩角控制型永磁同步电机直接转矩控制系统，文中提出并设计了一种变比例系数转矩PI调节器。为了减小电磁转矩与转矩角非线性关系这一因数给电机电磁转矩动态调节造成的误差，保证转矩在动态过程中准确而快速调节，文中通过对电机电磁转矩控制原理分析，给出转矩PI调节器中比例系数的最优设计方法；为了消除电机电磁一转矩稳态误差及保证系统工作的稳定性，借助系统的小信号模型推导出转矩PI调节器中积分系数设计原则，最后给出的实验结果证明了上述新型转矩PI调节器设计方法的可行性和有效性。