Fundamental characteristics of a brushless and self-excited sinusoidal-wave single-phase synchronous generator having a two-phase field winding excited by a half-wave rectified current

It is desired from the viewpoints of maintenance and construction to make single-phase synchronous generators of brushless and self-excited types. A novel brushless and self-excited single-phase synchronous generator was devised by one of the authors. The stator exciting current is made to flow simultaneously with the load current in the armature winding. Thus, the iron core for the magnetic circuit can be both for the synchronous generator itself and for the exciter. Experimental studies of the brushless and self-excited single-phase synchronous generator of which the rotor winding is used as a rotor exciting winding and a field winding are described in this paper. In the proposed generator, the rotor is provided with a balanced two-phase field winding to improve the voltage wave distortion. The terminal voltage of this generator can be kept constant in spite of the load variation. Therefore, the proposed synchronous generator can be expected to be used widely.     

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.     

A new self-excitation scheme for three-phase synchronous generators

A new self-excitation scheme has been developed for three-phase synchronous generators. The generator that uses this scheme behaves as a flat-compound machine without automatic voltage regulators. The stator of the generator is provided with an armature winding that generates the fundamental and 2nd-harmonic mmfs. The rotor is equipped with a field winding and a harmonic winding. The harmonic winding is magnetically coupled to the 2nd-harmonic mmf produced by the armature winding. The current flows in the stator armature winding by way of a three-phase set of capacitors connected across its three-phase terminals and the ac voltage is induced in the rotor harmonic winding due to the armature 2nd-harmonic mmf. By connecting the harmonic winding to the field winding through a rectifier circuit, self-excitation of the generator is obtained. This excitation scheme is both self-excited and brushless, and no exciter is required. Additionally, voltage regulation due to load variation can be improved by connecting suitable capacitors. In this paper the operating principle and circuit configuration of the generator are explained and the experimental results using a 1-kVA prototype machine are shown. The generator characteristics are theoretically clarified by approximate analysis, and appropriateness of the theory and the usefulness of the proposed scheme are experimentally confirmed.     

A New Brushless Half-Speed Synchronous Motor with Q-Axis Squirrel-Cage Damper Winding Driven by Voltage Source Inverter

A new brushless half-speed synchronous motor combined with a voltage source inverter is presented. The diode is inserted into one phase of the stator winding, and then the stationary magnetic field is superimposed on the revolving field. The rotor structure of the proposed motor is composed of the quadrature-axis (q-axis) squirrel-cage damper windings on the salient poles. By superimposing a stationary magnetic field on the stator, the motor is compelled to run at exactly half synchronous speed. For purposes of direct comparison the machine is tested with various configurations of damper windings. The experimental results are shown, and it is proved that the motor has excellent performance. The proposed brushless synchronous motor is very simple, robust, and maintenance-free.     

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.     

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.     

An exciterless- and brushless-type commutatorless motor fed from atransformer in parallel with a voltage source inverter

A novel exciterless- and brushless-type commutatorless motor driven by a voltage source inverter is presented, and the analysis of the characteristics and the test results are reported. In the commutatorless motor, the stator armature winding is connected electrically with the secondary winding of a transformer. An AC exciting current flows in the armature winding simultaneously with the load current. The ratio between the number of poles made by the load current and the number of poles by the AC exciting current is 2 or 1/2. Thus, the motor can be made exciterless and brushless. Since the rotating direction of the rotating field made by the AC exciting current is opposite to that of the rotor in this commutatorless motor, speed control in a low-speed range is possible, because a large current can flow in the field winding even if the rotor rotates in a low-speed range. As a result, the motor can be controlled in a wide range, from high speed to low speed. It has been found from the analysis and the test results that a shunt wound characteristic between the speed and the torque and other characteristics can be obtained     

基于双谐波绕组的混合励磁发电机励磁控制系统

为了解决不同运行工况下混合励磁同步发电机端电压恒定的问题,设计了一种基于全桥变换器拓扑的励磁控制系统。励磁系统采用以电枢绕组电压为外环、定子谐波励磁绕组电流为内环的双闭环控制策略,以谐波无刷混合励磁同步发电机端电压为反馈信号,通过调节定子谐波励磁绕组电流,以维持发电机端电压恒定。阐述了双谐波绕组的混合励磁发电机的基本结构和工作原理,设计了励磁控制系统的软硬件,并测试了励磁控制系统的性能。实验结果表明：调节定子谐波励磁绕组电流,可以很好的调节发电机的端电压;通过励磁控制系统的自动调节功能,实现了发电机在不同负载情况下的输出电压恒定。     

轴向磁通永磁同步电机气隙磁场解析计算

针对双定子单转子表面嵌入式轴向磁通永磁同步电机的气隙磁场进行了解析研究。建立了气隙磁场的解析模型,将轴向磁通电机等效成直线电机并建立了等效面电流模型来求解空载工况下的气隙磁场。根据电磁场理论中的唯一性定理,给出了满足泊松方程的边界条件,并将分离变量法应用于泊松方程的解析解来计算电机三相定子电枢绕组作用下的气隙磁场。通过将空载下的气隙磁场与电枢绕组作用下的磁场叠加来预测电机负载工况下的气隙磁场。最后用三维有限元仿真计算结果与解析模型的计算结果相比较,证明了解析法可以有效地计算轴向磁通电机的气隙磁场,为轴向磁通永磁同步电机的解析分析和优化设计提供了基本手段。     

直流电动机新论

作者在对新一代直流电动机(New DCM)的研究中发现并提出了直流旋转磁场这一电机学的新概念,是用换向控制器来控制电子换向器中功率开关管的导通状态及变化顺序,让通电直流电枢绕组磁势沿电枢表面圆周旋转而达到的。与交流旋转磁场一样,都是电枢绕组电路产生的磁势,它的旋转是由于电枢绕组线圈内电流瞬时值沿圆周分布变化引起的,与定转子机械相对运动没有关系。从转子的角度看电枢的旋转磁势是直流绕组电流还是交流绕组电流产生的并没有什么区别,所以对应不同的转子结构也能构成类似于交流同步电动机和交流异步电动机基本作用原理的电动机,又有所区别,出现了直流同步电动机和直流异步电动机的新概念和新名称。该文的研究有助于加深认识和开阔思路。     

Brushless DC Motors Using Unsymmetrical Field Magnetization

The prevalent types of brushless dc motors have evolved from the classical synchronous machine structures, using two-phase, three-phase, or four-phase stator windings and symmetrical N-S field magnetization patterns. The popular two-phase two-pulse brushless motor requires auxiliary means for starting and for ensuring relatively constant torque with rotor position. Three methods are used: 1) skewed stator poles, which introduce unsymmetrical air-gap reluctance and the resultant unsymmetrical air-gap magnetic field, 2) the Wessels design, which uses a rotor pole pattern of north-south-zero (N-S-0) and auxiliary stator poles, and 3) a combination of N-S-0 rotor pattern and 1200 electrical (el) pitch stator coils to produce an unsymmetrical air-gap magnetic field. The electromagnetic torque produced by motors using each of these methods is calculated using the coenergy method.     

磁阻式无刷双馈电机的转子结构及其性能分析

把磁阻式结构与绕线式转子结构相结合,提出一种具有磁阻式无刷双馈电机的转子结构。该转子结构既保持了绕线式转子绕线接线方式的灵活性,又发挥了磁阻式转子对磁通的导向作用,改善了电机的磁场调制效果,可以很好地实现转子与定子两套绕组耦合能力实现最大化。对磁阻式转子结构的无刷双馈电机的设计原理和方法进行了详细分析,以一台30k W样机为例说明了磁阻式无刷双馈电机的功率分配曲线、气隙磁通密度曲线和电机效率,并与磁障结构的磁阻式、加入笼条的磁阻式转子无刷双馈电机在同等条件下的电机输出功率作对比。最后对无刷双馈发电系统的动态特性进行样机实验,实验结果表明采用该方法设计的磁阻式无刷双馈电机具有优良的性能。     

两相无刷直流电动机及其系统仿真

两相无刷直流电动机控制简单，成本低，但转矩脉动大，制约了其应用。为此，该文在对其定、转子结构、绕组接线方式、位置传感器放置及工作原理进行分析的基础上，利用Matlab建立了电机及其驱动电路系统的仿真模型。分析及仿真结果表明，所研究的两相电机能产生平均转矩运行，有实际应用价值。     

三相无刷同步发电机转子绕组不同连接方式可靠性分析

电励磁三相无刷隐极同步发电机可通过改变励磁绕组电流大小改变气隙磁场强度,从而实现宽范围电压调节。转子绕组是三相无刷隐极同步发电机的重要组成部分,其一般采用同心式绕组。并联支路数为1的转子绕组极间、重间连接后,引出线正端与负端在铁心端面固定并直接引出。而并联支路数大于1的转子绕组不仅需要极间、重间连接,还需选择恰当的并联连接方式。不同的连接方式直接影响转子绕组的复杂性与可靠性。以10极5 MW三相无刷隐极同步发电机为例,对并联支路数为2的转子绕组不同连接方式进行比较。结合工艺性与可操作性,选择最优转子绕组连接方式,制作了发电机转子绕组以及样机。结果表明,该连接方式简单可靠,可提高产品工艺性,有效避免转子绕组绝缘故障。     

Analysis of armature reaction and winding inductances of permanent magnet brushless DC motor with deep slot concentrated coils

Based on the configuration of deep slot concentrated coils, an analytical model is developed for predicting the armature reaction field produced by the 3-phase stator windings of permanent magnet brushless DC motors with concentrated coils by using the image method and the analytical functions of the armature reaction and winding inductances are proposed accounting for the influence of stator slotting. This approach is different from the method of equivalent distributed current sheet and more suitable for electric machines, which have concentrated coils and deeper slots. Under different control mode, the different analytical functions are presented. This will be helpful when further analyzing the performance of the motor. The results agree with the experiment very well. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2005, 25(12): 127–132 (in Chinese)     

考虑铁心饱和的内置式永磁同步电机气隙磁场解析计算

准确分析电机结构以及磁饱和等因素对气隙磁场分布的影响是永磁电机设计、优化的关键。以分数槽集中绕组内置式永磁同步电机(FSCW-IPMSM)为研究对象,根据磁路分析方法和FSCW的分布规律,分别得到了考虑转子磁桥漏磁的空载永磁磁场解析模型和电枢反应磁场的解析表达式。考虑到定子齿槽结构以及转子内部永磁体分布,利用相对气隙磁导,将定子开槽和转子凸极对气隙磁场的影响考虑在内。重点结合定子铁心材料的B-H磁化曲线、定子铁心局部磁饱和特性引入铁心等效磁阻与动态磁导率来考虑定子铁心磁饱和对负载气隙磁场的影响。最后,有限元仿真和样机试验结果验证了理论分析的准确性,为该类电机的电磁设计和性能分析提供了理论基础。     

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.     

十二相同步电机空载特性及其绕组参数计算

针对凸极式同步推进电机的空载特性及其绕组参数与电机结构、定转子齿槽、磁场饱和等紧密相关的问题,分析了在不同励磁电流下同步推进电机相反电势的数值计算方法,提出了采用电机磁场能量微动法计算相绕组的参数,并对一台十二相同步推进电机的绕组参数及其空载特性进行了计算和测量。结果表明,提出的方法适用于分析多相同步推进电机的空载特性和绕组参数。     

Speed Control of a Brushless Static Kramer System

A new brushless speed control system is proposed which consists of a self-cascade induction motor and a brushless commutatorless motor. The slip power extracted from the stator terminals of the induction motor is converted to mechanical power by the commutatorless motor, which is coupled mechanically to the induction motor shaft. The field control method, the advance angle control method, and the dc chopper control method for speed variation are discussed. The experiments using a prototype self-cascade motor which has single-winding schemes both on the stator and rotor show that smooth peed variation can be achieved by dc chopper control. The proposed system offers the advantages of highly reliable, maintenance-free operation, and has less reactive power and smaller harmonic contents in supply lines than conventional systems.