稀土永磁无刷直流电动机原理.doc

稀土永磁无刷直流电动机原理1.稀土永磁无刷直流电动机的结构特点1.1无刷直流电动机（BLDCM）由电动机本体和驱动器构成，是一种典型的机电一体化产品。1.2电动机的定子绕组做成三相对称星行接法，同三相异步电动机十分相似。电动机转子由钕铁硼永磁材料构成。在定转子形成的气隙中产生N-S级相间的方波磁场，所以也把这种电动机称为“方波电动机”。为了使电动机绕组准确换向，在电动机内装有位置传感器，作为转子极性的位置信号1.3驱动器组成： 作为控制中枢的单片机； 作为电子换向的由IGBT或MOSFET构成的逆变桥； 作为电压型交一直一交主电路的整流、滤波单位； 作为人机接口的键盘和数字显示单位； 作为控制、驱动电源的开关电源。2.无刷直流电动机的主要特点2.1高效率：无刷直流电动机转子上既无铜耗也无铁耗，其效率比同容量异步电动机提高5%-12%。2.2功率因子高：无刷直流电动机无需从电网吸取激磁电流，功率因子接近1。2.3启动转矩大，启动电流小：无刷直流电动机的机械特性和调节特性与他激直流电动机枢控时相应特性类似，所以它的启动转矩大，启动电流小，调节范围宽，但没有因电刷换向器引起的缺点，电子换向取代了机械换向。2.4电动机出力高：该电动机的体积和最高工作转速相同时，较异步电动机输出功率提高30%。2.5适应性强：电源电压偏离额定值+10%或-15%，环境温度相差40K以及负载转矩从0100%额定转矩波动时，无刷直流电动机的实际转速与设定转速的稳态偏差，不大于设定转速1%。2.6无刷直流电动机是一种自控式调速系统，它无需像普通同步电动机那样需要启动绕组；在负载突变时，不会产生振荡和失步。2.7 无刷直流电动机具有直流电动机特性、交流异步电动机的结构。2.8 无刷直流电动机适合长期低速运转、频繁启动的场合，这是变频调速器拖动Y系列电动机不可能实现的。3.工作原理 无刷直流电动机由电动机主体和驱动器组成，是一种典型的机电一体化产品。电动机的定子绕组多做成三相对称星形接法，同三相异步电动机十分相似。电动机的转子上粘有已充磁的永磁体，为了检测电动机转子的极性，在电动机内装有位置传感器。驱动器由功率电子器件和集成电路等构成，其功能是：接受电动机的启动、停止、制动信号，以控制电动机的启动、停止和制动；接受位置传感器信号和正反转信号，用来控制逆变桥各功率管的通断，产生连续转矩；接受速度指令和速度反馈信号，用来控制和调整转速；提供保护和显示等等。无刷直流电动机的原理简图如图一所示：主电路是一个典型的电压型交-直-交电路，逆变器提供等幅等频5-26KHZ调制波的对称交变矩形波。永磁体N-S交替交换，使位置传感器产生相位差120的U、V、W方波，结合正/反转信号产生有效的六状态编码信号：101、100、110、010、011、001，通过逻辑组建处理产生T1-T4导通、T1-T6导通、T3-T6导通、T3-T2导通、T5-T2导通、T5-T4导通，也就是说将直流母线电压依次加在A+B-、A+C-、B+C-、B+A-、C+A-、C+B-上，这样转子每转过一对N-S极，T1-T6功率管即按固定组合成六种状态的依次导通。每种状态下，仅有两相绕组通电，依次改变一种状态，定子绕组产生的磁场轴线在空间转动60电度角，转子跟随定子磁场转动相当于60电度角空间位置，转子在新位置上，使位置传感器U、V、W按约定产生一组新编码，新的编码又改变了功率管的导通组合，使定子绕组产生的磁场轴再前进60电度角，如此循环，无刷直流电动机将产生连续转矩，拖动负载作连续旋转。正因为无刷直流电动机的换向是自身产生的，而不是由逆变器强制换向的，所以也称作自控式同步电动机。 无刷直流电动机的位置传感器编码使通电的两相绕组合成磁场轴线位置超前转子磁场轴线位置，所以不论转子的起始位置处在何处，电动机在启动瞬间就会产生足够大的启动转矩，因此转子上不需另设启动绕组。由于定子磁场轴线可视作同转子轴线垂直，在铁芯不饱和的情况下，产生的平均电磁转矩与绕组电流成正比，这正是他励直流电动机的电流-转矩特性。电动机的转矩正比于绕组平均电流；TM=Ktlav(N M)电动机两相组反电势的差比于电动机的角速度；ELL=Ke(V)所以电动机绕组中的平均电流为：Iav=(Vm-ELL)/2Ra(A)其中，Vm=VDC是加在电动机线间电压平均值，VDC是直流母线电压，是调制波的占空比，Ra为每相绕组电阻。由此可以得到直流电动机的电磁转矩：Tm=(VDC Kt/2Ra)-Kt(Ke/2Ra)Kt、Ke是电动机的结构常数，为电动机的角速度(rad/s)，所以，在一定的时，改变占空比，就可以线性地改变电动机的电磁转矩，得到与他励支流电动机电枢电压控制相同的控制特性和机械特性。无刷直流电动机的转速设定，取决于速度指令Vc的高低，如果速度指令最大值为+5V对应的最高转速：Vc(max),那么，+5V以下任何电平即对应相当的转速n，这就实现了变速设定。当Vc设定以后，无论是负载变化、电源电压变化，还是环境温度变化，当转速低于指令转速时，反馈电压Vfb变小，调制波的占空比就会变大，电枢电流变大，使电动机产生的电磁转矩增大而产生加速度，直到电动机的实际转速与指令转速相等为止；反之，如果电动机实际转速比指令转速高时，减小，Tm减小。发生减速度，直至实际转速与指令转速相等为止。可以说，无刷直流电动机在允许的电网波动范围内，在允许的过载能力以下，其稳定转速与指令转速相差在1%左右，并可以实现在调速范围内恒转矩运行。由于无刷直流电动机的励磁来源于永磁体，所以不象异步机那样需要从电网吸取励磁电流；由于转子中无交变磁通，其转子上既无铜耗又无铁耗，所以效率比同容量异步电动机高10%左右，一般来说，无刷直流电动机的能力指针（cos）比同容量三相异步电动机高12%-20%。 由于无刷直流电动机是以自控式运行的，所以不会象变频调速下重载启动的同步电动机那样在转子上另加启动绕组，也不会在负载突变时产生振荡和失步。中小容量的无刷直流电动机的永磁体，现在多采用高磁能积的稀土钕铁硼(Nd-fe-B)材料。因此，稀土永磁无刷电动机的体积比同容量三相异步电动机缩小了一个机座号。近三十年针对异步电动机变频调速的研究，归根到底是在寻找控制异步电动机转矩的方法，而无刷直流电动机的电流或电枢的端电压，就是直接控制电动机转矩的物理量。过去，由于稀土永磁体价格比较高等因素，限制了稀土永磁无刷直流电动机的应用领域，但是随着技术的不断创新，其价格已迅速下降，例如，我公司推出推出BS系列无刷直流电动机的售价已与异步电动机和普通变频器价格之和相差无几。稀土永磁无刷直流电动机必将以其宽调速、小体积、高效率和稳态转速误差小等特点在调速领域显现优势。电动机的定子绕组多做成三相对称星形接法，同三相异步电动机十分相似。电动机的转子上粘有已充磁的永磁体，为了检测电动机转子的极性，在电动机内装有位置传感器。驱动器由功率电子器件和集成电路等构成，其功能是：接受电动机的启动、停止、制动信号，以控制电动机的启动、停止和制动；接受位置传感器信号和正反转信号，用来控制逆变桥各功率管的通断，产生连续转矩；接受速度指令和速度反馈信号，用来控制和调整转速；提供保护和显示等等。 由于无刷直流电动机是以自控式运行的，所以不会象变频调速下重载启动的同步电机那样在转子上另加启动绕组，也不会在负载突变时产生振荡和失步。中小容量的无刷直流电动机的永磁体，现在多采用高磁能积的稀土钕铁硼（Nd-Fe-B）材料。因此，稀土永磁无刷电动机的体积比同容量三相异步电动机缩小了一个机座号。 近三十年来针对异步电动机变频调速的研究，归根到底是在寻找控制异步电动机转矩的方法，稀土永磁无刷直流电动机必将以其宽调速、小体积、高效率和稳态转速误差小等特点在调速领域显现优势。 无刷直流电机因为具有直流有刷电机的特性，同时也是频率变化的装置,所以又名直流变频,国际通用名词为BLDC。无刷直流电机的运转效率，低速转矩，转速精度等都比任何控制技术的变频器还要好，所以值得业界关注。Rare-earth permanent magnet brushless DC motor principle 1. Structural Characteristics of rare-earth permanent magnet brushless DC motor 1.1 Brushless DC motor (BLDCM) consists of a motor and a driver , is a typical integration of mechanical and electrical product. 1.2 The motor stator windings are made of symmetrical three-phase-line access, with the three-phase asynchronous motor is very similar. Permanent magnet motor rotor is made up of Nd Fe B material. Rotor in the formation of a gap in the phase of the NS-square magnetic field, so this motor also known as the square wave motor. In order to make accurate change to the motor windings, the contents are the motor position sensor, as the polarity of the rotor position signal 1.3 drive components: As the central control of the microcontroller; As to the electronic exchange from a MOSFET or IGBT inverter bridge; As a voltage reference to have been a reference to the main circuit of the rectifier, filter units; As a man-machine interface keyboard and digital display units; As a control, power supply switch power. 2. The main characteristics of Brushless DC motor 2.1 high efficiency: brushless DC motor rotor, neither iron nor consumption of copper consumption, compared with the efficiency of its capacity asynchronous motor increased by 5% -12%. 2.2 high power factor: brushless DC motor without magnetizing current lessons from the power grid, power factor is close to 1. 2.3 Big starting torque, small starting current: brushless DC motor and the mechanical properties of regulation with his shock when the DC motor drive control corresponding characteristics similar, so its starting torque, starting current small, wide scope of regulation, but no Brush commutator caused by the shortcomings of electronic exchange to replace the mechanical commutation. 2.4 high-output : the size of the motor and a maximum speed of the work at the same time, more asynchronous motor power output increased 30 percent. 2.5 adaptability: supply voltage rating from +10% or 15%, the environment and the temperature difference of 40 K load torque from 0-100% rated torque fluctuations, brushless DC motor speed and set the actual speed of stability State deviation, not more than set speed 1%. 2.6 brushless DC motor is a governor-controlled system, it need not like the general need to start as synchronous motor windings; mutation in the load, does not produce oscillations and out-of-step. 2.7 brushless DC motor of a DC motor, AC asynchronous motor structure. 2.8 brushless DC motor for long-term low-speed operation, launched frequent occasions, this is VVVF drag-Y Series Motor unattainable. Principle Brushless DC motor from the main motor and drive components, is a typical integration of mechanical and electrical products. Motor stator windings made more symmetric star to three-phase, three-phase asynchronous motor with very similar. Motor rotor on a stick has been magnetizing the permanent magnet, in order to detect the polarity of motor rotor, a built-in motor position sensor. Drive from power electronic devices and integrated circuits, such as composition, its functions are: to accept the motor start, stop, the brake signal to control the motor start, stop and braking; accept the position sensor signals and positive and signals used to control inverse Variable bridge the power of the on-off, a continuous torque; acceptable rate of speed instructions and feedback signals, used to control and adjust the speed; provide protection and display, and so on. BLDCM diagram of the principle as shown in Figure 1: The main circuit is a typical cross-voltage - straight - cross circuit, inverter and other sites, such as providing 5-26 KHZ frequency modulation wave symmetry alternating rectangular wave. Magnet NS alternate exchange, a position sensor 120 phase of the U, V, W square, combine / signal an effective reversal of the six state code signal: 101,100,110,010,011,001, through Logic set up a deal with T1-T4-on, T1-T6-on, T3-T6-on, T3-T2-on, T5-T2-on, T5-T4-on, meaning that DC will be followed by increases in bus voltage A + B-, A + C-, B + C-, B + A-, C + A-, C + B-, so each rotor passed a very NS, T1-T6 of power at a fixed portfolio that is Into the six-state status in order. Each state, only winding two-phase electricity, followed by a change in status, the stator windings of the magnetic field axis of rotation in space-degree angle, 60 , with the rotor stator rotating magnetic field, equivalent to 60 degree angle space position, the rotor New location, the position sensor U, V, W have agreed on a new set of codes, the new code also changed the power of the on-portfolio so that the stator windings of the magnetic field axis, then forward 60 degree angle, so cycle , Brushless DC motor will have a continuous torque, drag the load for continuous rotation. It is precisely because of the brushless DC motor for the self-generated, rather than by the inverter to the mandatory exchange, also known as-controlled synchronous motor. Brushless DC motor position sensor encoded so that the two-phase electricity winding axis of the magnetic field position ahead of the rotor magnetic field axis position, regardless of the starting position in the rotor where the motor launch will have a big enough moment the start-up torque, Therefore, no separate rotor start winding. As the stator magnetic field can be regarded as the axis with the vertical axis of the rotor, the core is not saturated in the case, the average torque and winding current is directly proportional, this is his current DC Motors, Mr Patrick - torque characteristics. Motor torque proportional to the average current Winding; TM = Ktlav (NM) Motor two-phase group of potential anti-poor than in the motor angular velocity; ELL = Ke (V) so the average motor winding current is: Iav = (Vm - ELL) / 2Ra (A) which, Vm = VDC is the increase in inter-voltage electrical line average, VDC is DC bus voltage, is the duty cycle modulation wave, Ra for each of the winding resistance. This can be DC motor torque: Tm = (VDC Kt/2Ra)-Kt (Ke / 2 Ra) Kt, Ke is the motor of the structure constant, motor for the angular velocity (rad / s), therefore, Certain , change the duty cycle , you can change the linear motor torque, be with him, Mr Patrick tributaries motor armature voltage control of the same control and mechanical properties. Brushless DC motor speed settings, depending on the level of speed command Vc, if the maximum speed of command for the +5 V corresponding maximum speed: Vc (max), then, +5 V below any level that corresponds considerable speed n, This realization of a variable speed settings. When Vc set after both the load changes, changes in supply voltage or temperature changes, when the speed below the speed command, the feedback voltage Vfb smaller, the duty cycle modulation wave will be larger, armature ER , So that the electromagnetic motor torque generated increasing acceleration, until the actual speed and motor commands the same speed until the contrary, if the motor speed than the actual instruction at high speed, reduced, Tm decreases. Reduction in speed, until the actual speed and direction of the same speed. It can be said that brushless DC motor fluctuations in allowing the power grid, within the allowed Guozainengli below its speed and stability of the difference in speed commands about 1%, and the governor could be achieved within the framework of constant torque operation. As brushless DC motor excitation from the permanent magnet, so I do not like asynchronous machines, as required draw from the grid exciting current Because of the rotor without alternating magnetic flux, its rotor neither iron nor consumption of copper consumption, the efficiency of Asynchronous motor with a high capacity of around 10 percent, in general, the ability of brushless DC motor indicators ( cos ) than the three-phase asynchronous motor with high-capacity 12% -20%. As a brushless DC motor-controlled operation, so as not Frequency Control under heavy start of the synchronous motor, as in the rotor plus a start winding, and will not load when a mutation oscillations and out-of-step. The capacity of small and medium-sized brushless DC permanent magnet motor, use of high-energy product of rare earth NdFeB (Nd-fe-B) materials. Therefore, rare earth permanent magnet brushless motors the size of the same capacity than the three-phase asynchronous motor narrow a machine Zuohao. Nearly 30 years for motor asynchronous Frequency Control of the final analysis, is looking for asynchronous motor torque control method, and brushless DC motor armature of the current or voltage is in direct control of the physical motor torque . The past, because of rare earth permanent magnet relatively higher prices, limiting the rare earth permanent magnet brushless DC motor applications, but with technological innovation, its price has been rapidly declining, for example, I launched the company launched BS series brushless DC motor With the price of ordinary asynchronous motor and inverter, and is almost the same price. Rare-earth permanent magnet brushless DC motor is bound to its wide speed range, small size, high efficiency and steady speed and other characteristics of small errors in the field show speed advantage. The motor stator windings are made of symmetric star to three-phase,which is very similar to three-phase asynchronous motor.Motor rotor has a stick magnetizing the permanent magnet,.To detect the polarity of motor rotor, a motor position sensor is built-in. The driver includes power electronic devices and integrated circuits, such as composition, its functions are: to accept the motor start, stop, the brake signal to control the motor start, stop and braking; accept the