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.     

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.     

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.     

交直流混合供电同步发电机暂态性能的研究

将电机的多回路理论与有限元方法相结合建立了交直流混合供电同步发电机的数学模型,讨论了阻尼绕组和励磁绕组端部漏感的计算方法,采用关联变换建立绕组,整流桥与负载间的联接,考虑了由于凸极效应,磁路的饱和,绕组的布置以及定转子齿槽的影响产生的空间谐波磁场的作用,对发电机的交流侧和直流侧突然短路过程进行了仿真,仿真结果与试验结果进行了比较以证明数学模型的正确性。     

一种简易的无刷直流电机微机控制系统

设计了基于MCS51系列单片机控制的无刷直流电机调速系统,并分析了系统的控制策略,提出了相通电实现零相位控制方式的恒转矩运行,通过三相通电实现超前相位控制方式的恒功率运行,实验证明该方法是可行的。     

凸极同步电动机起动时电磁场数值计算

以一台凸极同步电动机为例,给出了基本假设和边界条件,利用正弦时变场原理和有限元法,并以端电压和磁感应强度为收敛条件,对凸极同步电动机起动时的电磁场和定子绕组的电流进行了分析和计算,并与实测结果进行对比.分析研究了起动时凸极同步电动机磁场的分布和谐波,得出了一些有益的结论.     

永磁无刷直流电机空载气隙磁场和绕组反电势的解析计算

该文利用许－克变换构造了考虑齿槽效应的气隙相对比磁导函数，该气隙相对比磁导函数反映了齿槽效应对气隙磁场分布的影响，且这种影响的程度随气隙中的径向位置而变化，在忽略铁心饱和的情况下，结合偏微分方程的解析算法，提出了一种考虑齿槽效应的永磁无刷直流电机空载气隙磁场分布和相绕相反电动势的解析计算方法，计算结果与二维有限元计算结果对比，其计算波形和大小吻合很好，证明此方法是正确的、可靠的、为永磁无刷直流电机优化设计和性能分析提供了基本分析手段。     

Microcomputer Control for Sensorless Brushless Motor

The microcomputer control of a brushless motor without a shaft position sensor is studied. A method which permits the determination of the permanent magnet rotor position by the back electromotive force (EMF) induced in the stator windings and the starting technique which uses the motor as a synchronous motor at standstill are explained. The motor voltage is chopped by commutator transistors to change the motor speed. The control system consists of a 4-b single-chip microcomputer and two quad-comparators.     

同步电动机结构对交交变频矢量控制系统性能的影响

从传统的交交变频同步电动机矢量控制系统出发，研究了同步电动机的结构、联结方式及阻尼绕组结构对系统性能的影响，提出定子三相绕组分别联结，具有全阻尼绕组结构的隐极同步电动机更适合交交变频器供电的矢量控制系统，并使系统性能更优。     

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。     

Excitation scheme of brushless self-excited-type three-phasesynchronous machine

AC excitation schemes of a brushless self-excited-type three-phase synchronous machine are presented. The rotor field windings of the machine are short circuited with the diodes, and an exciter or other exciting equipment is not required in this machine. On the positive-phase-sequence rotating field of the stator, the plural rotating fields with different speeds from it are superimposed by using a machine-side voltage source PWM inverter/converter, and the field MMF is obtained by half rectifying AC voltages induced in the rotor field windings. Two excitation schemes are proposed that have the advantage of the reduction of the torque pulsation as compared with the scheme that superimposes the singular rotating field with a different speed from the positive-phase-sequence field. This is confirmed by simulation, and experimental results are given     

阻尼绕组对磁场定向控制交－交变频同步电机动态行为的影响

本文在交－交变频磁场定向控制同步电机调速系统数学模型的基础上，研究了阻尼绕组对交－交变频同步电机动态行为的影响．结果指出．阻尼绕组能有效地抵消动态电枢反应，加快定子电流响应，提高电机的过载能力．从改善系统的动态特性出发，应选择全阻尼结构。     

集中绕组永磁无刷直流电机电枢反应及绕组电感的解析计算

基于深槽集中绕组的结构特点，采用镜像法，建立了适合集中绕组无刷电机的电枢反应求解模型。充分考虑电机齿槽影响，给出了电枢反应磁场的解析表达式，对不同控制方式下的电枢反应分别作了研究，并在此基础上推导了电机绕组电感的通用求解公式，从而为集中绕组无刷电机的参数设计和特性分析提供了理论依据。样机实验表明，其具有很好的工程适用性，理论计算与实测值吻合。     

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.     

双余度无刷直流电机电枢绕组结构对比

建立了双余度无刷直流电机的数学模型,初步确定了定子绕组采用半球缠绕结构和隔槽嵌放结构情况下电机余度之间的耦合关系。在Ansoft Maxwell环境下针对两种结构的双余度无刷直流电机余度间耦合情况做了进一步分析验证,证明两种结构下余度间耦合程度的一致性。另外,通过对两种结构样机的实际测试和对比,证明了两种结构双余度无刷直流电机机械特性的一致性。两种结构具有相同的余度间耦合程度以及相同的机械特性,在部分对功率密度以及磁热耦合要求较低的场合具有通用性。     

永磁无刷直流电机负载磁场及其电磁转矩的计算

该文在考虑齿槽影响的前提下，建立了永磁无刷电机电枢反应磁场的解析计算模型，求出永磁电机相绕组的自感和互感。在对水磁无刷直流电机空载气隙磁场和空载相绕组反电动势求解的基础上，结合永磁无刷直流电机主电路的拓扑结构，构造出电机绕组的场路耦合模型，由此计算出电机相绕组电流变化波形。在考虑齿槽影响情况下，计算出永磁电机在任意时刻的电枢反应磁场和负载气隙磁场，进而计算出永磁无刷直流电机产生的瞬时电磁转矩，以便定量分析永磁无刷电机的电磁转短被动和绕组换相引起的转矩被动，为分析永磁无刷直流电机的工作特性和振动噪声提供了可靠的依据。     

同步发电机阻尼绕组和磁路饱和对低频振荡阻尼的影响

采用特征值分析法研究同步发电机阻尼绕组以及磁路饱和对低频振荡阻尼的影响。建立了同步发电机三阶以及考虑阻尼绕组的六阶小扰动线性化模型,并在模型中考虑了磁路饱和效应。为详细分析同步发电机阻尼绕组和磁路饱和对低频振荡阻尼的影响,采用了简化的单机无穷大系统。计算表明,在分析低频振荡问题时:同步发电机三阶模型不宜用于分析进相或轻载运行的机组,这一结论和是否安装电力系统稳定器(PSS)以及是否忽略磁路饱和无关;忽略磁路饱和的同步发电机三阶模型在额定工况附近具有比较高的准确性;磁路饱和对六阶模型的影响较小,但是对于含PSS的进相运行机组,不宜忽略磁路饱和;为得到准确的结论,建议在同步发电机模型中考虑阻尼绕组和磁路饱和的影响。     

Characteristics of a permanent magnet type bearingless motor

Super high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high power drives can be achieved with bearingless motors. In this paper, a bearingless motor with the principles of permanent magnet type synchronous motors is proposed. High power factor and high efficiency can be expected in permanent magnet type bearingless motors. The proposed bearingless motor is a 4 pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. It was found that radial forces are efficiently produced by employing thin permanent magnets on the surface of rotor iron core. A test machine was built in order to measure inductance functions as well as relationships between voltages and currents     

Analysis and characteristics of a permanent magnet-type bearingless motor

Super-high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high-power drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet-type synchronous motors is proposed. High-power factor and high efficiency can be expected in permanent magnet-type bearingless motors. The proposed bearingless motor is a 4-pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. The relationships between radial forces and the permanent magnet thickness were derived. From these relationships, the optimal permanent magnet thickness to produce radial forces efficiently is found. A test machine was built to confirm the relationships of radial forces, currents and voltages.