Brushless self-excited three-phase synchronous generator without exciter

This paper describes principles together with analytic and experimental studies of an exciterless, brushless, and self-excited three-phase synchronous generator which was devised by authors. Since traditional brushless and dc self-excited three-phase synchronous generators without exciter did not have the self-exciting function by series characteristic component proportional to the load current inside the generator, they need auto-voltage regulating equipment or a transformer with three windings and condensers to obtain constant voltage characteristics. It also has the following problem in the case of two-pole traditional generator: oscillatory tension is generated at the shaft of the rotor caused by the magnetic force between magnetic poles of stator and rotor windings, and it causes mechanical vibration and noise. This paper proposes a new brushless and self-excited three-phase generator solving the aforementioned problems: the ratio of poles of the windings for providing power to load (armature and field windings) to the windings for supplying exciting power (stator and rotor exciting windings) is 1 to 5. Then oscillatory tension does not generate theoretically. Furthermore, a self-exciting three-phase generator using the 5th-harmonic component of armature reaction which makes series characteristic component proportional to the load current, currently is available. In this paper, the winding construction, the electric circuit, and the principle of the aforementioned generator are described, and the experimental results of the trial-produced generator show that the three-phase terminal voltage waveforms are almost sinusoidal and also balanced, and the voltage can be kept almost constant for the change of load. This generator has high reliability because of its simple construction.     

Self-regulated self-excited brushless three-phase synchronous generator

For lightweight and compact implementation of a generation set, many attempts have been made by some researchers to develop a brushless self-excited synchronous generator without an ac exciter. A previous paper proposed a novel self-excitation scheme by which the second-space harmonic component of armature mmf is used for exciting the rotor field system. In this excitation scheme the effect of the series excitation characteristic, as well as a self-excited and brushless implementation without an ac exciter is automatically obtained. However, in the case of system configuration of the generator already reported, voltage regulation in the inductive load condition was very large. To remove this problem, this paper presents a new system configuration of the generator with a self-regulating feature that can compensate voltage regulation automatically. The new generator consists of a stator installing two three-phase windings, externally connected to a load and a capacitor bank, respectively, and a rotor with field and harmonic windings. In this paper the system configuration and theoretical concepts of the presented generator are described and detailed experimental investigations with a laboratory machine are also shown.     

Analysis of characteristics of half-wave rectified brushless synchronous motor with permanent magnets

Previously, the authors proposed a “half-wave rectified brushless synchronous motor” as a novel servomotor. The rotor winding emf of the motor is induced by the stator current mmf which rotates at synchronous speed and pulsates at bias frequency. The field excitation is produced by the field current obtained from rectifying the emf with a diode inserted into the field winding. To improve the power factor and the efficiency, they also proposed a new-type half-wave rectified brushless synchronous motor with permanent magnets. This paper analyzes the flux distribution and the torque characteristics of the new half-wave rectified brushless synchronous motor using the finite element method. The computed torque characteristics are confirmed with the experimental results. Furthermore, the steady-state characteristic equations are derived and the effect of the modulation function waveforms on the motor performance is investigated. The theory also is confirmed by the experiments.     

Characteristics of a brushless and exciterless three-phase synchronous generator with DC exciting system

From the viewpoint of maintenances and constructions, it is desirable that brushless and exciterless type three-phase synchronous generators be made. To meet this requirement, one of the authors devised a brushless and exciterless synchronous generator in which exciting currents flow simultaneously with load currents in armature windings. Thus, generators can be used both as the generators themselves and as the exciters. A generator system has already been reported by one of the authors. In it, the dc stator exciting current flows between the middle points per phase of the double-star armature winding through the rectifiers. However, the winding connection between the armature winding and the rectifiers are complicated. Three sets of rectifiers are needed by the stator excitation. The authors present a generator system by which the electric connection of between the stator armature winding and the rectifier can be simplified, and the number of the rectifiers can be reduced. In this system, the stator is provided with a double-star armature winding having two neutral points. In this paper, first, a circuit constitution and the principle for the brushless and exciterless three-phase synchronous generator are described, and second, the characteristics are elucidated by means of characteristic analysis. Further, the results of the experiments for the generator conducted on the test machine of 2.0 kW are shown.     

阻尼绕组对凸极同步发电机空载电势波形的影响

采用二维瞬态涡流场有限元法，对装有阻尼绕组的凸极同步发电机的空载电势波形进行了计算，分析了阻尼绕组节距对空载电势波形的影响。结果表明，阻尼绕组可以削弱定子齿谐波分量，而对与阻尼绕组节距有关的谐波分量则有加强作用。     

同步发电机整流系统的分析方法和研究领域

同步发电机整流系统的广泛应用以及其多类型的系统结构和运行方式 ,形成了一个以该系统为对象的研究领域 ,本文对该系统的分析方法和研究所涉及的领域进行了综合性的讨论 ,归纳总结出分析该系统的主要分析方法和研究领域。     

Analysis of brushless four-pole three-phase synchronous generatorwithout exciter by the finite element method

The magnetic field analysis of the original brushless four-pole three-phase synchronous generator is described. The rotor of the generator consists of short-circuited field coils with diodes. The output voltage can be kept constant by adjusting the stator DC current. To analyze the characteristics of this generator, the direct finite element method, in which the values of currents and magnetic vector potentials can be directly obtained, is applied. It is found that the results of this theoretical analysis agree well with the experimental results     

Analysis of the self-excited three-phase synchronous generator utilizing the second space harmonic for excitation

In a previous paper, we proposed a new self-excited three-phase synchronous generator in which the second space harmonic component of the armature reaction field is used for exciting the field system, and clarified its operating principles and basic characteristics by experiment. The new generator has a series excitation characteristic, and responds quickly to a sudden change of load, because an excitation power can be directly obtained from the armature reaction field. This paper introduces a method for analyzing the steady-state performance of our new generator. In the analysis, an equivalent circuit of the generator is derived from a duality between interlinked electric and magnetic circuits. A simple determination method of parameters in the equivalent circuit is also shown. Calculated results are compared with the experimentally obtained values on a laboratory machine, and good agreement between both values has been observed. The proposed analysis is useful for simulating the steady-state performance of the generator by taking into account the nonlinear effect of the iron core due to magnetic saturation. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(1): 70–81, 1997     

A brushless three-phase synchronous motor using the armature winding as both load and DC excitation winding

This paper presents a new brushless three-phase synchronous motor which has no exciter. The technique applied to the motor provides an effective way for conventional brushless synchronous motors to simplify the system configuration. The stator of the motor is equipped with a double-star connected armature winding which has two neutral points. The rotor is a cylindrical one, which is equipped with a two-phase field winding. The field winding is connected with shaft-mounted rectifiers. A dc voltage is applied to the two neutral points of the armature winding to obtain the rotor excitation when the motor is operated at synchronous speed. At that time. the armature winding acts as a stator dc exciting winding while also acting as a load winding. In this paper the principle and characteristics of the motor are described. and the experimental results are shown. It is confirmed that with a 2-kW experimental machine, the proposed motor has good performance. For example, by adjusting the stator dc current, this motor power factor can easily be controlled within a wide range.     

宽转速范围永磁同步发电机电流矢量控制

为了实现永磁同步发电机(PMSG)在宽转速范围内和变负载条件下的高性能稳压控制,提出一种基于PWM整流器的PMSG电流矢量控制策略。PMSG输出的不稳定交流电经过PWM整流器变换成稳定的直流电,这样的直流发电系统具有高功率密度、高效率和能量、可双向流动等优点。所述的电流矢量控制策略,具体是在PMSG低速时采用最大转矩/电流比(MTPA)控制,中高速时通过一个电压外环实时补偿d轴弱磁电流,使得PMSG系统能够根据转速和负载变化及时地分配和控制d、q轴电流。仿真和实验结果验证了该控制策略的正确性和有效性,实现系统在宽转速范围的高性能稳压输出。     

永磁同步发电机齿槽转矩削弱方法研究

永磁同步发电机在风力发电系统中应用越来越广泛,然而由永磁体与有槽定子铁芯之间的相互作用产生的齿槽转矩,会引起振动和噪声,并影响风力发电系统的控制精度。文章推导了基于能量法和傅里叶分解的齿槽转矩表达式,分析了削弱齿槽转矩的影响因素,提出了一种基于开辅助齿的削弱齿槽转矩的方法。在此基础上,给出了开辅助齿情况下的傅里叶分解系数,并分析了辅助齿宽度以及辅助齿高度对齿槽转矩的影响。最后利用有限元法对其进行了验证,结果表明,采用1/3槽宽的辅助齿宽度时,齿槽转矩基波分量减小了39.08%,有限元方法计算结果证明得出的结论是正确有效的,所得结论可为进一步优化永磁电机设计提供理论依据。     

谐波励磁同步发电机空载谐波磁场分析

说明了利用ANSYS有限元分析软件的电磁分析功能对谐波励磁同步发电机空载谐波磁场进行分析,通过对谐波励磁同步发电机的电磁场进行计算,得出了样机的矢量磁位Az、磁力线分布图和磁密分布图。然后对电磁场的计算结果进行后处理,得出了谐波励磁同步发电机的旋转磁场波形、谐波绕组电压波形和谐波绕组空载特性曲线。最后用在谐波励磁同步发电机上的实验结果与计算结果的比较说明了方法的正确性,可为谐波励磁同步发电机的设计提供理论依据。     

混合磁极式的混合励磁永磁同步发电机仿真

为了研究混合磁极式的混合励磁永磁同步发电机转子上既有永磁体、又有励磁绕组的运行性能,建立了混合磁极式的混合励磁永磁同步发电机的基本方程;根据该电机的转子结构及定子绕组的实际连接方式和空间分布情况,分析了模型中电感参数及永磁体在其他回路中产生的磁链的特点,并给出其表达式;采用有限元法计算各参数表达式中的系数,能准确考虑磁极形状及永磁体的作用,利用数值方法对该电机的性能进行仿真.在1台混合磁极式的混合励磁永磁同步发电机样机上进行了实验,仿真结果和实验结果吻合较好,验证了仿真模型的正确性和参数计算的准确性.     

Characteristic analysis and trial manufacture of permanent‐magnetic type linear generator

This paper describes the design and trial manufacture of a linear generator which can convert any mechanical vibration of an automobile to electrical energy. A mover, which includes permanent magnets, is linearly driven through a stator by vibrations. The Nd‐Fe‐B magnets in the mover are placed facing the same magnetic poles in order to produce a change of magnetic flux in the coils of the stator. The coils are placed in the stator with the same intervals as the magnets. Successive coils are wound in opposite directions and are connected in series. A magnetic iron core covering the stator makes the magnetic flux extend through the case and reduces flux canceling in the coils of the stator. The distribution of the magnetic field, the electromotive force, and the driven power of the mover were calculated by numerical simulations in order to determine the size of the linear generator. A linear generator and experimental apparatus were built on the basis of the simulation. The performance characteristics were tested in experiments, and the produced linear generator was confirmed to be useful as an onboard auxiliary power supply. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 94– 100, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20751     

Magnetic field analysis of a 70‐MW‐class superconducting generator by the 3D finite element method

The three‐dimensional magnetic field and eddy current distribution of the 70‐MW‐class superconducting generator was calculated by a finite element method. The condition for the exciting armature coil was calculated by the jω‐method. In the magnetic flux distribution of the armature winding bore, the value obtained by analysis had good agreement with the measurement. An analysis that let the rotor move by the synchronizing speed was also done. The armature voltage for the nonload condition and the armature current for the three‐phase short‐circuit condition obtained by calculations had good agreement with the measurements. The validity of the analytical model for three‐dimensional magnetic field analysis of superconducting generators was confirmed from these results. In addition, the synchronous reactances were calculated using these results with eddy current in the facing. It was found that the facing had the effect of decreasing synchronous reactance by about 5%. © 2000 Scripta Technica, Electr Eng Jpn, 134(2): 53–60, 2001     

大型同步发电机内全流场数值计算与分析

依据计算流体力学理论,应用有限体积法对大型同步发电机定子通风沟流体速度进行了计算与分析,并且对全流场中,由于转子旋转离心作用转子内流体速度(转子旋转流体场)对定子径向通风沟流体速度的影响进行了仿真计算与分析,得出一些有益的结论.     

航空同步发电机波梯电抗分析及求取方法

航空同步发电机用零功率因数负载特性和空载特性所测得的波梯电抗数值比正常值大,致使在电机分析和计算中无法使用。为了解决航空电机的实用参数精确测试问题,分析了航空电机的结构特点,解释了出现这一现象的主要原因是由于励磁绕组漏磁增大。并给出一种利用励磁磁路饱和系数修正过饱和磁路励磁电抗的求取方法。用本方法对一台航空同步发电机的测试数据进行了计算,求得的结果比较合理。     

混合励磁永磁同步发电机的电磁场有限元分析

介绍了一种混合励磁永磁同步发电机的电磁场有限元分析，这种发电机的主发电机部分和一般的永磁同步发电机相同，样机采用了表面径向式磁钢转子，另有用于调节电压的辅助电励磁部分，两部分共有一套电枢绕组。为了精确计算该发电机的参数和特性，采用了电磁场有限元计算，特别是对磁场分布比较复杂的电励磁部分采用了三维电磁场分析，在有限元数值计算的基础上，推导了计算发电机外特性的等效电路，并加工了实验样机，样机实测数据和计算结果相吻合。     

Analysis of a self‐regulated,self‐excited,brushless three‐phase synchronous generator,which includes the effect of core losses

This paper presents a novel analysis of a self‐regulated, self‐excited, brushless three‐phase synchronous generator, which includes the effect of core losses. The core losses are modeled by equivalent core loss resistances connected to additional windings on the generator's magnetic coupling model. A magnetic circuit is drawn from the magnetic coupling model, and an electrical equivalent circuit of the generator is derived by utilizing a duality between the magnetic and electric circuits. Using this equivalent circuit, the generator's steady‐state performance is theoretically predicted, and the results are verified through experiment. In addition, the power losses during power generation are analyzed quantitatively. The proposed analysis takes into account the nonlinearity of the exciting impedances due to magnetic saturation. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 51–60, 2000     

Analysis of terminal voltage waveform of AC exciting synchronous generators

Recently, adjustable speed hydroelectric power systems have been developed. In those power systems, ac exciting synchronous generators are used instead of the ordinary salient-pole-type synchronous machines. However, some higher harmonic sequences are included in the distribution of air-gap magnetic flux density and in the terminal voltage waveform of the ac exciting synchronous machines because these machines have open winding slots. To develop better machines without terminal voltage waveform distortions, an evaluation method of the terminal voltage harmonics has been needed. This paper describes the mechanism of higher harmonics generation qualitatively and proposes an analytical method of no-load terminal voltage waveforms on the basis of two-dimensional magnetic field analysis considering movement of the rotor for quantitative higher harmonics analysis. The analytical results of higher harmonics show good agreement with the experimental ones.