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。     

无取向电工钢片旋转磁特性测量与损耗特性分析

设计低耗、高效变压器和电机离不开对铁心的磁化特性与损耗性能的精准把握。实际运行工况下,铁心中同时存在交变磁场和旋转磁场,且交变磁场和旋转磁场存在着本质的不同,因此探究电工钢片在旋转磁场下的磁化特性和损耗性能就显得至关重要。本文以电机定子作为电工钢片旋转磁特性励磁装置,通过电机的三相励磁绕组产生椭圆形旋转磁场,给出两相输出反馈到三相输入的控制策略,研究不同磁化角度、轴比对损耗特性的影响。并分析了传统正交分解损耗模型在高磁通密度下计算误差较大的原因,提出修正模型,解决了原模型在高磁通密度下存在较大计算误差的问题,为优化设计新一代高效率变压器、电机奠定基础。     

球面电磁电动机

正1电磁电动机的工作原理如图1所示的电动机中,外侧和内部转子均为永磁体,这样在磁力的作用下,外侧或内部的转子就可以产生旋转。如果使外侧转子按箭头所示方向旋转,那么内部转子就会沿相同方向旋转。如果用电磁铁取代外侧永磁体,而内部转子仍然保持永磁体,那么外侧电磁铁转子旋转时,由于旋转磁场的作用,内部转子会同样旋转,这便形成了可以将电能转换为旋转力的电磁电动机。     

三绕组单相电容电动机可以实现全域圆旋磁场

普遍单相电容电机,仅能做到在某一运行点(或两点)上获得圆形旋转磁场,本文将导出在定子上具有三个以上绕组结构条件下,可以做到从起动到同步速的全部运行范围内皆为圆形旋转磁场。并提供一组配合参数供参考。     

角加速度直接测量方法研究与异步电机测量实例

提出的旋转系统机械角加速度直接测量方法通过对交流异步测速发电机励磁方式的改变,构成了能直接测量机械角加速度的测旋转角加速度发电机.它可以直观地反映出各种旋转系统随时间变化的机械角加速度的变化情况,可应用于旋转系统机械角加速度快速变化的测量场合.用此方法测量了异步电机空载运行时由旋转磁场振动而引起的转子角加速度的变化情况,证明了测量方法的可行性.此方法在科研生产中有一定应用价值.     

直线电机机械手

(一)直线电机的基本原理直线电机是由电能直接产生机械直线运动的一种新型电机。任何型式的旋转电机原则上都可以变成直线电机。直线感应电动机是由普通感应电动机直接演变而来的。因此,两者的基本原理是一样的。通常广泛应用的交流感应电动机是鼠笼型感应电动机。它由两部分组成:固定不动的定子和作旋转运动的转子。定子上嵌有三相交流绕组,当以平衡的三相交流电流接至此绕组时,气隙中便会产生旋转磁场。在此磁场作用下,转子上感应出电流。转子电流与旋转磁场相互作用产生的力矩,使转子沿旋转磁场的方向转动起来。对直线电机,我们可以用旋转电机来设想。将一台旋转电机在它的任意一点沿轴向剖开,然后展开铺平,使原来的圆形定转子都展开成直线的平板形。由定子演变而来的一侧叫初级,由转子演变而来的一侧叫次级。这时,如果给初级绕     

饱和凸极及绕组非对称性对高频信号注入法估计转子位置的影响

永磁电机除了物理凸极,还存在由于磁路饱和所产生的饱和凸极,饱和凸极主要对定子漏电感产生影响;电机绕组在物理上也可能不对称,从而产生一个椭圆形的旋转磁场.这两种因素的互相作用,使得高频负序电流的谐波含量增加,给转子位置的估计带来误差.本文对这一问题进行了理论研究和实验验证.初步阐释了负序谐波电流产生的原因及造成的影响,并...     

光驱故障排除实例

一、一台ACER CD912E光驱,不读盘,放进盘之后,“吱吱”响几下,然后自动将盘退出。 拆开后发现光头组件很新,而且没有明显的损坏迹象,便接上电源空载观察,光头能正常循迹检索,这表明光头或光驱电路部分应该没太大问题。放入一张光碟重新开机试验,同样旋转几下后便停住退盘,似有异物卡住,仔细观察见光驱内部压盘部位有一小团丝状物卡入其中,造成光盘在旋转时受阻停转,将其取出,故障消除。 事后分析,杂物有可能是厂家在装配时混入,或用户在放置光盘时随手带入的。     

关于交流电机中“二相对称”概念的分析

0 引言交流旋转电机实现机电能量转换的介质是由旋转磁动势在气隙中产生的旋转磁场.三相电机由于绕组间的磁链彼此互相耦合,使得三相电机的动态数学模型复杂,它是一个高阶、非线性、强耦合的多变量系统,控制困难,使用不方便.为了使用电机的动态数学模型,就需要对数学模型进行化简,化简的基本方法就是坐标变换.     

三柑异步电动机在转子阻抗不对称时的运行探讨

1.引言当三相异步电动机定子接入三相对称电压时,在气隙中将产生一旋转磁场,并在转子各相感应出转差频率的电势和电流。由每一转差频率的相电流建立的气隙磁场,将包含一个相对转子为转差转速、正向旋转的分量和一个大小相同的以同样转速反向旋转的分量。若转子是对称的,反向旋转磁场的合成分量为零;若不对称则不为零。该磁场以(2S-1)倍的同步转速相对于定子反向旋转,故在定子绕组中感应出频率为(2S-1)f的电势。因此,定子中将包含基频分量和(2S-1)倍基频分量的电流。     

Zero magnetic field type magnetic field sensor

This paper presents a new magnetic field sensor named the zero magnetic field type, on the basis of its principle of operation, which is as follows: when the magnetic field level in the core used as a sensor is shifted by an unknown field to be detected, a controlled field is so superimposed in the opposite direction to the unknown field that the original zero magnetic field state is resotred. Then the unknown field can easily be detected from the controlled field. Consequently, detection performance is expected to be unaffected by geometrical configurations, magnetization properties, and demagnetization effects of the core used as a sensor. Moreover, temperature variations of the core and the existence of resistance and leakage inductance in the windings arranged on the core also do not directly degrade performance. This paper certifies that the proposed sensor certainly has the forementioned properties. In addition, the following are clarified: (1) the upper limit of the detectable range does not exist in principle; (ii) the accuracy is 0.02 percent for the full scale 20 kA/m and realizes the order of 4 × 10^?4 percent/^oC for temperature variations of ?76^o C to 300^oC; (iii) the magnetization property required of the core used as a sensor is that it has as sharply a rectangular B-H loop as possible; (iv) as a result, sensor design is greatly simplified.     

无源高温超导磁浮轴承磁悬浮力的计算

本文应用有限元方法和超导临界态理论，推导了高温超导体电流分布和电流密度计算方程。由高温超导体电流计算了高温超导磁浮轴承悬浮力。利用实验测量结果验证了此方法的有效性。     

Storing magnetic data

Magnetic recording data storage innovation and product evolution is arguably higher than it has ever been. For example, the current record in high density recording is 23.8 Gbit/in², which was demonstrated by Seagate Technology. Data is stored by creating a pattern of magnetization in the media using a recording head. Basically, the head is a split ring-shaped core of easily magnetized material wrapped by a few turns of wire. When current flows in the wire, it induces a magnetic flux in the core and a field across the recording gap. Reversing the current's direction changes the direction of the magnetic field. Because the field lines spread out as they bridge the gap, they magnetize the media in a small zone near the gap. Since data is stored as binary digits, a pattern of current reversals can be coded to represent binary digits. For example, “1” might be represented by a magnetization reversal and “0” by the absence of a reversal. Data is read by sensing the fields that arise from the magnetization transition zones in the media. These fields are caused by a concentration of magnetic poles at the ends of each magnetized region. Since these fields point in the opposite direction to the media's magnetization, they are called “demagetizing fields” These fields extend beyond the media's surface. Thus, they can induce responses in a read head if it is brought close to the media     

Adjustable magnetic gear

A mathematical interpretation of a combined electromechanical device possessing the properties of a synchronous machine connected to a frequency converter and of a magnetic gear with a variable reduction factor is considered. The stator winding of the synchronous machine is concentrated (tooth winding), and its spatial period covers the full number of teeth z. An expression for the frequency response of the magnetomotive force (MMF) of the tooth winding was obtained. In the variant under consideration (z = 36), the fundamental harmonic of the magnetic field, which sets the number of stator pole pairs, is v = p = 17. The MMF of the magnets of the internal rotor is represented as a Fourier series. Formulas are given making it possible to calculate the magnetic fields in two air gaps of the magnetic gear caused by the stator current and magnets of a high-speed rotor (using the method of specific magnetic conductivity). The electromagnetic torques of the gear shafts are calculated by the stretch method. The electromagnetic torque caused by the stator winding is determined on the basis of the instantaneous values of the EMF of rotation and transformation of each winding coil without using the winding coefficients. A differential equation system for calculating the transient processes in three channels of a wind-power plant is obtained: in two mechanical channels and in one electrical channel. A closed system with a PID controller is proposed making it possible to stabilize the rotational speed of the electric generator of a wind-power plant with a variable wind speed.     

磁梯度张量在磁体测距中的应用研究

磁测距技术具有全方向定位、对环境依赖低等优点,拥有广阔的应用空间.传统的磁测距技术以磁场总量测量为主,但计算量大,定位实时性差.针对这一不足,在磁偶极子模型的基础上建立了磁梯度张量测距模型.通过欧拉反褶积法理论推导出磁梯度张量定位的距离公式,根据该公式确立了5传感器测距模型,并以霍尼韦尔5883L微型磁阻传感器为核心设计、制作了磁梯度张量测距仪.经过实验验证,该测距仪具有短程测距的功能,可以有效测量1m内目标磁体距离.该结果表明,利用磁梯度张量测量距离的方法是行之有效的,且具有较高的精度.     

采用Halbach磁场的新型被动磁轴承仿真

为了提高永磁磁轴承的轴向承载力和刚度,在对理想Halbach磁场进行分析的基础上,利用分段磁环构成的近似Halbach磁场设计了一个新型的轴向永磁磁轴承.通过有限元软件对这种磁轴承进行了建模仿真,计算了最大承载力以及刚度,并分析了磁环的厚度与高度比值对磁轴承刚度的影响.仿真结果表明,采用Halbach磁场的轴向磁轴承最大可以提供2×106N/m的刚度,高于相同永磁材料用量条件下传统轴向磁轴承的刚度.考虑到这种磁轴承的结构要比传统结构复杂,因此这种磁轴承更适合在对刚度要求高的场合应用.