Steady-state performance of a line-start synchronous reluctance motor with capacitive assistance

This paper sets forth the steady-state performance analysis of a connection scheme that improves the power factor and torque with a lower magnetizing current for a line-start synchronous reluctance motor. The machine stator winding is split into two equal halves, one connected to the mains and the other connected to a balanced capacitor. Performance of the machine is improved if the capacitor value is such that the winding to which it connected operate at or very close to resonance in the d-axis. Current in both windings contributes positively to torque production and external control circuitry is not required. Steady-state equations arising from the d–q model gives a direct insight on the operating limits and how this capacitance aids the machines torque and power factor by boosting its direct axis reactance while the quadrature axis reactance remains fairly constant. An equivalent circuit is also deduced from the steady-state equations from which an explicit expression for input impedance of the new machine can be derived. Conditions for unity-power factor at varying load conditions are also examined. A comparison with conventional single-winding synchronous reluctance motor is given. Such comparison is fair because both machines have the same amount of copper and iron. Experimental results are provided to validate the analytical results.     

直线同步电机运行分析

为了深入研究直线电机的稳定运行特性,根据Maxwell原理,建立了分析直线同步电机稳态的电磁场数学模型.采用有限元方法进行离散,计算直线电机的磁场分布及电磁力,并开发了直线电机性能分析软件.软件计算得出直线电机悬浮力和推力随功角、电流变化等特性曲线的结果与ANSYS的计算结果一致,并具有模型简单、计算快速等优点,分析结果可为直线电机运行提供理论依据.     

Performance analysis of self-controlled synchronous motors considering the effects of magnetic saturation

A self-controlled synchronous motor, which has similar characteristics to a conventional dc motor, is being used in various industrial fields as an adjustable speed motor. The inductances in the motor are changed with change in the air-gap flux due to magnetic saturation (as in a field-weakening region). A new and simple formula representing the inductances (i.e., reactances), in which the effect of magnetic saturation is taken into account, is proposed in this paper. The validity of the formula is shown for the transient performances of a tested motor when the field voltage was stepped down. The effects of magnetic saturation on the steady-state and dynamic performances are then clarified for a motor having average constants of synchronous machines. It is shown that the steady-state motor speed for small values of dc input current when the magnetic saturation is considered is larger than that for constant parameters. It is also clarified that the field-weakening speed control regions for constant-power driving become narrow if the motor has the property of considerable magnetic saturation. The transient responses when dc input and field voltages are changed, respectively, are finally investigated; it is shown that if magnetic saturation is considered, the commutation limit of inverter thyristors for a step-down change in the field voltage is widened when compared with the case for constant parameters. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 56–69, 1997     

Classical analysis of static stability of a salient-pole synchronous motor

Sufficient conditions for static stability of a salient-pole synchronous motor are found by two methods. The equivalence of these methods is proved. The synchronous motor is demonstrated to be statically unstable under superconductivity conditions, even if it is equipped with a damper winding.     

Performance analysis of a reluctance synchronous motor under abnormal operating conditions

In recent years, the application of reluctance synchronous motors to ac drives has been gaining importance. In this paper, the performance of such motors under abnormal operating conditions (such as voltage unbalance) is analyzed and compared to their performance under normal conditions by means of motor current signature analysis. In order to permit an objective comparison of the simulation and experimental results, the influence of the supply time harmonics and constructional asymmetries of the machine is also considered. Detailed mathematical proofs are provided to support the results. Such analysis will be helpful for understanding and identifying stator inter-turn faults unambiguously. To the best knowledge of the authors, such an analysis has not been carried out previously.     

永磁感应子式无刷直流电动机的转矩特性研究

针对永磁感应子式无刷直流电动机的定转子齿结构和绕组的排列对转矩特性的影响,从特定电机结构的磁导计算出发,推导出永磁感应子式无刷直流电动机的参数表达式,分析了电机的参数特征对转矩工作特性的影响。实验及分析表明,采用等效磁路和实际测量相结合的方法．可以预测永磁感应子式无刷直流电动机的电磁转矩和齿槽定位力矩特性,为电机的转矩控制提供理论依据。     

Transient performance analysis for permanent-magnet hysteresis synchronous motor

The combination of hysteresis and permanent-magnet materials in the rotor of a self-starting synchronous motor makes the motor analysis very difficult due to its inherent nonlinearity. This paper presents the simulation results of the transient performance of permanent magnet hysteresis synchronous (PMHS) motors. The major feature in this study is to combine the time-stepping finite-element technique with the model for B-H hysteresis loop in order to take the nonlinear magnetic hysteresis into account. The good agreement between computed and measured performance in a laboratory PMHS motor validates the proposed analysis.     

Dynamic analysis of synchronous motor using vector diagrams-anintuitive approach

Vector diagrams have been used for many years to help understand the physical behavior of electric machines and to give geometrical answers to a number of machine operating problems. Vector diagrams for a synchronous machine in steady operational conditions or even at the first instant of a transient state are a quite common means of analyzing the machine performance. This paper shows the application of vector diagrams to represent the behavior of a synchronous motor during a transient process. As an example, the dynamic power diagram is introduced, showing the oscillation of the rotor following a sudden change in the motor operation. The intention of the paper is also to point out the contribution of the intuitive mind to the solution of technical problems, usually neglected in our educational system. It is the author's belief that the visualization obtained from geometric constructions is particularly useful for teaching purposes, since nowadays, the widespread use of computers to solve numerically the machine equations tends to divert the student's attention from the actual physical phenomenon occurring during the performance of the electrical machines     

分段式永磁直线同步电动机有限元分析

为了研究提升系统的分段式永磁直线同步电动机(PMLSM)的运行特性,首先建立了其稳态有限元分析模型,分析了不同动子位置时电机的磁场分布,计算了不同动子位置、不同电枢电流时电机的静态力-位移-电流特性,得到电磁参数随动子位移及电枢电流的变化曲线;然后建立了分段式PMLSM的时步有限元分析模型,对分段绕组两两并联供电方式下,起动过程的动态特性进行了计算,得到动态过程中电枢电流、感应电动势、电磁力、动子运行速度、位移等物理量随时间变化过程.经实验测试验证了分析结果的正确性.     

Design of a synchronous reluctance motor drive

A segmental-rotor synchronous reluctance motor is used in a variable-speed drive with current-regulated pulse-width-modulated (PWM) control. The low-speed torque capability is compared with that of an induction motor, a switched reluctance motor, and a brushless DC PM motor of identical size and copper weight. A particular point of interest is the comparison of motors of different types, all with essentially the same frame size and tested under identical conditions. The results suggest that many of the desirable properties of the switched reluctance motor can be realized with the synchronous reluctance motor but with using standard AC motor and control components. The torque capability is lower, but so is the noise level     

PWM逆变器——磁阻同步电动机驱动系统运行稳定性的分析

研究了由PWM逆变器供电的磁阻同步电动机的运行稳定性,导出了dq0坐标系中PWM 逆变器-磁阻电动机的小信号模型,以稳定度λ作为稳定性能的指标,应用Rout-Hurwitz判据判定系统的稳定性,并分析了电机和系统参数对运行稳定性的影响,所得结论对变频磁阻电动机的设计具有参考价值。     

某凸极同步电动机转子三维温度场计算与分析

为了确保凸极同步电动机的寿命和运行可靠性,获得电机转子内部准确的温度分布及其特点是非常重要的。以国内目前单机容量较大的27 MW凸极同步电动机为研究对象,建立了1/8整机内部流场与1/8转子固体结构模型。基于计算流体动力学(CFD)原理,应用有限体积法,首先求解转速为1 500 r/min的额定工况下的1/8整机内部定转子流场。然后,求解包含1/8转子固体结构的三维湍流流固耦合温度场。计算结果表明:整个转子部分峰值温度位于中心对称面处铜绕组中,相邻绝缘层的最高温度为125.7℃未超温,电机安全运行。     

Identification of machine parameters of a synchronous motor

This paper presents a method for estimating the machine parameters of a synchronous motor. The presented method is equally applicable for a wound field synchronous motor, synchronous reluctance motor, or permanent magnet (PM) synchronous motor, both the interior and surface-mount types. The method works particularly well for machines having a significant amount of space harmonics, such as synchronous reluctance and interior PM (IPM) machines, where the harmonics are predominantly the slot harmonics. It is also well suited for surface PM machines operating under saturation, where the harmonics are saturation-induced. The presence of these harmonics makes the parameter identification difficult. Most of the methods presented so far in the literature have failed to properly identify machine parameters in the presence of space harmonics. In this paper, the machine parameters, identified by using a proposed algorithm, are compared with the finite element and the experimental results to demonstrate the effectiveness of the presented method. Both interior PM and surface PM machines are considered.     

超导同步电动机温度场计算与分析

为判断高温超导电机超导体及永磁体运行的稳定性,准确计算电机内的温度场十分必要.以全超导样机热性能为研究对象,首先利用时步有限元方法建立二维正弦时变电磁场模型,得到了电机定转子损耗分布.根据传热学原理,通过数值分析给出定子表面散热系数的计算方法.然后计算分析高温超导电机的温度场.通过计算结果与实测数据的对比分析,验证所给...     

On-line efficiency optimization of a synchronous reluctance motor

This paper deals with an on-line optimum-efficiency control of a synchronous reluctance motor drive. The input power minimization control is implemented with a search controller using Fibonacci search algorithm. It searches the optimal reference value of the d-axis stator current for which the input power is minimum. The input power is calculated from the measured dc-bus current and dc-bus voltage of the inverter. A rotor-oriented vector control of the synchronous reluctance machine with the optimization efficiency controller is achieved with a DSP board (TMS302C31). Experimental results are presented to validate the proposed control methods. It is shown that stability problems can appear during the search process.     

六相电励磁同步风力发电机组的稳态模型

六相电励磁同步风力发电机(SP-EESWG)是一种特殊的变速恒频风电机组。以风电机组各部分的数学模型为基础,详细考虑风力机的风能利用特性、整流-逆变电路的稳态特性,以及机组所采用的最大风能跟踪控制、直流电容电压控制和并网逆变器控制对稳态特性的影响,建立了SP-EESWG的稳态模型,并将其应用于含SP-EESWG电网的潮流计算。最后,以单机无穷大系统和IEEE 14节点系统两个算例验证了所提模型的正确性和有效性。仿真结果表明,不同风速情况下,现有文献广泛采用的风电机组简化潮流模型与该模型的计算结果均有不同程度的误差。其中,一阶和二阶简化模型的误差较大,不宜用于SP-EESWG的稳态特性分析;当风速处于额定风速附近时,三阶简化模型与该模型的误差可以忽略。     

Self-excited synchronous induction motor

A synchronous-induction motor, with the features of both a synchronous motor and a wound-rotor induction motor, far excels other synchronous motors in starting characteristics. However, a major drawback of the synchronous-induction motor is the need for an excitation power supply with low-voltage, large-current power rating. For this reason, its driving equipment becomes large, and increases overall cost. This paper proposes a new synchronous-induction motor, absent the problems involved in making the motor a self-excited type. It employs the second-space harmonic component of armature reaction field to obtain the self-excitation of the field system, and installs a harmonic winding, which is used for extraction of an excitation power, in the rotor. This new self-excited motor has the following advantages: (1) the driving equipment is small, since no excitation power supply is involved; and (2) due to the effect of the series characteristic by which the field current varies in proportion to the load current automatically, the motor can be operated with a good power factor. In the present paper the structure and operating principle of the new motor are explained and the basic characteristics are also investigated by means of a simple analysis and experimental results with a 1.5-kV trial machine.