外文翻译--感应电动机的起动方法和问题.doc

INDUCTION MOTOR STARTING METHODS AND ISSUES感应电动机的起动方法和问题Abstract Many methods can be used to start large AC induction motors. Choices such as full voltage, reduced voltage either by autotransformer or Wyes - Delta, a soft starter, or usage of an adjustable speed drive can all have potential advantages and trade offs. Reduced voltage starting can lower the starting torque and help prevent damage to the load. Additionally, power factor correction capacitors can be used to reduce the current, but care must be taken to size them properly. Usage of the wrong capacitors can lead to significant damage. Choosing the proper starting method for a motor will include an analysis of the power system as well as the starting load to ensure that the motor is designed to deliver the needed performance while minimizing its cost. This paper will examine the most common starting methods and their recommended applications.摘要： 许多方法可用于启动大型交流感应电动机。选择如全电压，通过自耦变压器或Y形三角电压降低，软起动器，或可调速驱动器的使用都可以有潜在的优势和权衡。降压起动可以降低起动转矩，防止损坏负载。此外，校正电容器可用于降低功率因数，但必须注意正确的尺寸。错误的电容器的使用可能会导致重大损失。选择适当的启动方法，电机将包括为保证电机的设计提供了所需的性能的同时，最大限度地降低其成本的初始荷载的动力系统分析。本文将最常用的起动方法和推荐的应用研究。Index Terms: motor starting. Reduced voltage start auto transformer, wyes-delta, power factor correction索引条款：电动机起动。降压起动自耦变压器，Y形三角洲，功率因数校正INTRODUCTION There are several general methods of starting induction motors: full voltage, reduced voltage, wyes-delta, and part winding types. The reduced voltage type can include solid state starters, adjustable frequency drives, and autotransformers. These, along with the full voltage, or across the line starting, give the purchaser a large variety of automotives when it comes to specifying the motor to be used in a given application. Each method has its own benefits, as well as performance trade offs. Proper selection will involve a thorough investigation of any power system constraints, the load to be accelerated and the overall cost of the equipment.简介：有起动异步电动机的几种常见方法：全电压，降低电压，Y形三角洲，和部分绕组类型。低电压型可包括固态启动器，变频驱动器，和自耦变压器。这些，连同全电压，或直接起动，给买方的汽车种类繁多的时候指定在给定的应用程序中使用的电机。每种方法都有其自身的利益，以及性能的权衡。正确的选择会涉及的任何权力制约制度进行彻底的调查，以加速负载设备的整体成本。In order for the load to be accelerated, the motor must generate greater torque than the load requirement. In general there are three points of interest on the motors speed-torque curve. The first is locked-rotor torque (LRT) which is the minimum torque which the motor will develop at rest for all angular positions of the rotor. The second is pull-up torque (PUT) which is defined as the minimum torque developed by the motor during the period of acceleration from rest to the speed at which breakdown torque occurs. The last is the breakdown torque (BDT) which is defined as the maximum torque which the motor will develop. If any of these points are below the required load curve, then the motor will not start.为了使负载能加速，电机必须产生更大的扭矩比负荷要求。一般有三点对电机转速的扭矩曲线的兴趣。第一个是锁定转子扭矩（LRT），最小转矩，电机将在剩下的所有的角位置的转子。二是拉转矩（放），定义为最小转矩由电动机在加速期从其余的速度，转矩发生。最后是击穿扭矩（BDT）被定义为最大转矩，电机的发展。如果这些点所需的负荷曲线的下方，然后电机不能启动。The time it takes for the motor to accelerate the load is dependent on the inertia of the load and the margin between the torque of the motor and the load curve, sometimes called accelerating torque. In general, the longer the time it takes for the motor to accelerate the load, the more heat that will be generated in the rotor bars, shorting ring and the stator winding. This heat leads to additional stresses in these parts and can have an impaction motor life.这需要对电机的加速负载的时间是依赖于负载的惯量和电动机的转矩与负载曲线之间的边缘，有时也被称为加速转矩。一般来说，越需要电机的加速负载时，其会在转子产生更多的热量，短路环和定子绕组。这种热导致这些部件的附加应力，可以有一个影响电机的寿命。II. FULL VOLTAGE The full voltage starting method, also known as across the line starting, is the easiest method to employ, has the lowest equipment costs, and is the most reliable. This method utilizes a control to close a contactor and apply full line voltage to the motor terminals. This method will allow the motor to generate its highest starting torque and provide the shortest acceleration times. This method also puts the highest strain on the power system due to the high starting currents that can be typically six to seven times the normal full load current of the motor. If the motor is on a weak power system, the sudden high power draw can cause a temporary voltage drop, not only at the motor terminals, but the entire power bus feeding the starting motor. This voltage drop will cause a drop in the starting torque of the motor, and a drop in the torque of any other motor running on the power bus. The torque developed by an induction motor varies roughly as the square of the applied voltage. Therefore, depending on the amount of voltage drop, motors running on this weak power bus could stall. In addition, many control systems monitor under voltage conditions, a second potential problem that could take a running motor offline during a full voltage start. Besides electrical variation of the power bus, a potential physical disadvantage of an across the line starting is the sudden loading seen by the driven equipment. This shock loading due to transient torques which can exceed 600% of the locked rotor torque can increase the wear on the equipment, or even cause a catastrophic failure if the load can not handle the torques generated by the motor during staring.II。全压全电压起动方法，也被称为直接起动，是采用最简单的方法，具有最低的设备成本，是最可靠的。该方法利用一控制关闭接触器应用全电压的电机端子。这种方法将使电机产生最高的起动转矩和提供最短的加速时间。这种方法也提出了最高的菌株对电力系统由于高的起动电流，一般可以在六到七倍的电机电流正常满负荷。如果电机是电力系统薄弱，突然的高功耗可引起电压暂降，不仅在电机端子，但整个电源总线送起动电机。此电压下降将导致电机的起动转矩下降，下降和转矩的任何其他电机电源总线上运行。开发的感应电动机的转矩变化大致为所施加的电压的平方。因此，根据电压下降量，电机在这一弱势客车运行可能失速。此外，电压条件下监测许多控制系统，一个潜在的问题，可以采取离线运行电动机全电压起动时。除了电源总线的电性变化，一个潜在的直接起动的物理缺点的驱动设备，看到突然加载。这种冲击加载由于暂态扭矩可超过600%的锁定转子扭矩可增加对设备的磨损，甚至导致灾难性的故障，如果负载不能处理在盯着由电机产生的转矩。A. Capacitors and Starting Induction motors typically have very low power factor during starting and as a result have very large reactive power draw. See Fig. 2. This effect on the system can be reduced by adding capacitors to the motor during starting. 答：电容起动异步电动机通常有非常低的功率因数在起动和结果具有非常大的功画。见图2。这对系统的影响可以通过增加电容器的电机起动时降低。The large reactive currents required by the motor lag the applied voltage by 90 electrical degrees. This reactive power doesnt create any measurable output, but is rather the energy required for the motor to function. The product of the applied system voltage and this reactive power component can be measured in VARS (volt-ampere reactive). The capacitors act to supply a current that leads the applied voltage by 90 electrical degrees. The leading currents supplied by the capacitors cancel the lagging current demanded by the motor, reducing the amount of reactive power required to be drawn from the power system. To avoid over voltage and motor damage, great care should be used to make sure that the capacitors are removed as the motor reaches rated speed, or in the event of a loss of power so that the motor will not go into a generator mode with the magnetizing currents provided from the capacitors. This will be expanded on in the next section and in the appendix.大反应电流的电机滞后电压90电角度的要求。这无功不产生任何可测量的输出，而是用于电机的功能所需的能量。应用系统的电压的乘积这功分量可测变量（乏）。电容器的行为提供一电流，使电压90电角度。领先的电流由电容器提供取消滞后电流通过电机的要求，减少需要从电力系统绘制功量。为了避免过电压和电机损坏，须特别小心，以确保电容器作为电机达到额定转速的删除，或在断电时使电机不会从电容器提供励磁电流，发电机模式。这将扩大对下一节和附录中。B. Power Factor Correction Capacitors can also be left permanently connected to raise the full load power factor. When used in this manner they are called power factor correction capacitors. The capacitors should never be sized larger than the magnetizing current of the motor unless they can be disconnected from the motor in the event of a power loss.B.功率因数校正电容器还可以留下永久连接到提高全负荷功率因数。当以这种方式使用它们被称为功率因数校正电容器。电容器不应尺寸大于磁化电流的电机除非他们可以断开电机在断电的情况下。The addition of capacitors will change the effective open circuit time constant of the motor. The time constant indicates the time required for remaining voltage in the motor to decay to 36.8% of rated voltage after the loss of power. This is typically one to three seconds without capacitors.另外的电容器将改变有效开路时间常数的电机。时间常数表明剩余电压在电机额定电压衰减到36.8%的功率损失后所需的时间。这通常是一个三秒的无电容器。With capacitors connected to the leads of the motor, the capacitors can continue to supply magnetizing current after the power to the motor has been disconnected. This is indicated by a longer time constant for the system. If the motor is driving a high inertia load, the motor can change over to generator action with the magnetizing .与连接到电机的引线电容器，电容器可以在电动机的电源已断开，继续提供磁化电流。这是一个较长的时间常数为系统显示。如果电机是驱动大惯性负载，电机可以改变与励磁发电机行动。Current from the capacitors and the shaft driven by the load. This can result in the voltage at the motor terminals actually rising to nearly 50% of rated voltage in some cases. If the power is reconnected before this voltage decays severe transients can be created which can cause significant switching currents and torques that can severely damage the motor and the driven equipment. An example of this phenomenon is outlined in the appendix.从电容器和轴驱动的负载电流。这可能会导致在电机端子实际上在上升至近50%，在某些情况下，额定电压在电压。如果重新连接电源之前，这个电压衰减严重的瞬变可以创建可引起明显的开关电流和扭矩，会严重损坏电机和驱动设备。这种现象的一个例子是在附录中列出了。Ill. REDUCED VOLTAGE Each of the reduced voltage methods are intended to reduce the impact of motor starting current on the power system by controlling the voltage that the motor sees at the terminals. It is very important to know the characteristics of the load to be started when considering any form of reduced voltage starting. The motor manufacturer will need to have the speed torque curve and the inertia of the driven equipment when they validate their design. The curve can be built from an initial, or break away torque, as few as four other data points through the speed range, and the full speed torque for the starting condition. A centrifugal or square curve can be assumed in many cases, but there are some applications where this would be problematic. An example would be screw compressors which have a much higher torque requirement at lower speeds than the more common centrifugal or fan load. See Fig. 3. By understanding the details of the load to be started the manufacturer can make sure that the motor will be able to generate sufficient torque to start the load, with the starting method that is chhosen.生病。降低电压的电压降低的方法的目的是降低电机起动电流对电力系统的电压控制，电机将在终端。这是了解负载的特点是启动时考虑任何形式的降压起动很重要。汽车制造商将需要转速扭矩曲线和驱动设备的惯性，当他们验证他们的设计。该曲线可由初始，或脱离扭矩，只有其他四个数据点的速度范围内，和全转速转矩的起动条件。离心式或平方曲线可以在许多情况下，假设，但也有一些应用，这将是有问题的。一个例子是，螺杆压缩机具有更高的扭矩要求在较低的速度比一般离心泵或风机负载。见图3。通过了解负载的细节必须开始制造商可以确保电机能产生足够的转矩启动负载，具有起动方法，chhosen。A. Autotransformer 答：自耦变压器The motor leads are connected to the lower voltage side of the transformer. The most common taps that are used are 80%, 65%, and 50%. At 50% voltage the current on the primary is 25% of the full voltage locked rotor amps. The motor is started with this reduced voltage, and then after a pre-set condition is reached the connection is switched to line voltage. This condition could be a preset time, current level, bus volts, or motor speed. The change over can be done in either a closed circuit transition, or an open circuit transition method. In the open circuit method the connection to the voltage is severed as it is changed from the reduced voltage to the line level. Care should be used to make sure that there will not be problems from transients due to the switching. This potential problem can be eliminated by using the closed circuit transition. With the closed circuit method there is a continuous电机引线连接到变压器的低压侧。这是最常用的水龙头80%，65%，和50%。在50%上的电压电流是25%次全电压锁定转子电流。电机启动这个降低的电压，然后在一个预先设定的条件达到连接切换到线电压。这种情况可能是一个预先设定的时间，目前的水平，总线伏，或电机速度。的变化可在一个闭合电路的过渡，还是一个开放的电路转换的方法。在开放电路电压的连接方法是作为它是从低电压变为水平线。护理应用于确保不会有问题，从瞬变由于开关。这个潜在的问题可以通过使用闭路过渡消除。与闭回路法有一个连续的Voltage applied to the motor. Another benefit with the autotransformer starting is in possible lower vibration and noise levels during starting.施加到电动机的电压。在启动过程中的另一个好处与自耦变压器起动在尽可能低的振动和噪音水平。Since the torque generated by the motor will vary as the square of the applied voltage, great care should be taken to make sure that there will be sufficient accelerating torque available from the motor. A speed torque curve for the driven equipment along with the inertia should be used to verify the design of the motor. A good rule of thumb is to have a minimum of 10% of the rated full load torque of the motor as a margin at all points of the curve.由于电机产生的转矩会随着所施加的电压的平方变化，要特别注意确保有足够的加速转矩可以从电机。用于驱动设备，随着惯性力矩速度曲线可以用来验证电机设计。一个好的经验法则是有一个最低的额定满负载转矩的电动机10%作为所有点的曲线边缘。Additionally, the acceleration time should be evaluated to make sure that the motor has sufficient thermal capacity to handle the heat generated due to the longer acceleration time.此外，加速时间应进行评估，以确保电机由于较长的加速时间产生足够的热容量的热处理。B. Solid State or Soft Starters B.固态软起动器These devices utilize silicon controlled rectifiers or Scars. By controlling the firing angle of the SCR the voltage that the device produces can be controlled during the starting of the motor by limiting the flow of power for only part of the duration of the sine wave.这些器件采用可控硅整流器或疤痕。通过控制触发角的晶闸管电压，该装置产生可控制的电动机起动过程中通过限制只有正弦波的时间部分功率流。The most widely used type of soft starter is the current limiting type. A current limit of 175% to 500% of full load current is programmed in to the device. It then will ramp up the voltage applied to the motor until it reaches the limit value, and will then hold that current as the motor accelerates.软起动器使用最广泛的类型是类型的电流限制。电流限制为175%到500%的满负荷电流编程的装置。然后它会增加电机电压直至达到极限值，然后就认为，电流为电动机的加速。Tachometers can be used with solid state starters to control acceleration time. Voltage output is adjusted as required by the starter controller to provide a constant rate of acceleration. The same precautions in regards to starting torque should be followed for the soft starters as with the other reduced voltage starting methods. Another problem due to the firing angle of the SCR is that the motor could experience harmonic oscillating torques. Depending on the driven equipment, this could lead to exciting the natural frequency of the system.转速表能与固态起动器用于控制加速时间。输出电压是由起动器必须提供一个恒定的速率加速调整。在以相同的预防措施，启动转矩应遵循的软起动器与其他降压起动方法。由于可控硅的触发角的另一个问题是，电机能经历谐波振荡的扭矩。根据驱动设备，这可能会导致令人兴奋的系统的自然频率。 C. Adjustable Frequency Drives C.变频驱动器This type of device gives the greatest overall control and flexibility in starting induction motors giving the most torque for an amount of current. It is also the most costly.The drive varies not only the voltage level, but also the frequency, to allow the motor to operate on a constant volt per hertz level. This allows the motor to generate full load torque throughout a large speed range, up to 10:1. During starting, 150% of rated current is typical.This allows a significant reduction in the power required to start a load and reduces the heat generated in the motor, all of which add up to greater efficiency. Usage of the AFD also can allow a smaller motor to be applied due to the significant increase of torque available lower in the speed range. The motor should still be sized larger than the required horsepower of the load to be driven. The AFD allows a great degree of control in the acceleration of the load that is not as readily available with the other types of reduced voltage starting methods.这种类型的设备提供了最大的整体控制和灵活性，在起动异步电动机给最转矩电流量。它也是最昂贵的。驱动的变化不仅电压水平，而且频率，使电机在一个恒定的伏特每赫兹级操作。这使电机产生满负载转矩在整个调速范围大，可达10:1。在启动过程中，额定电流的150%是典型的。这允许启动所需的负载功率的显着减少，并降低了电机产生的热量，所有这些总计达更高的效率。渔农处的使用也可以允许一个较小的电机是由于可用的扭矩在较低的速度范围内显着增加的应用。电机仍应尺寸大于所需的功率来驱动负载。渔农处允许的负荷，是不是加速容易获得与其他类型的降压起动控制方法很大程度上。The greatest drawback of the AFD is in the cost relative to the other methods. Drives are the most costly to employ and may also require specific motor designs to be used. Based on the output signal of the drive, filtered or unfiltered, the motor could require additional construction features. These construction features include insulated bearings, shaft grounding brushes, and insulated couplings due to potential shaft current from common mode voltage. Without these features, shaft currents, which circulate through the shaft to the bearing, through the motor frame and back, create arcing in the bearings that lead to premature bearing failure, this potential for arcing needs to be considered when applying a motor/drive package in a hazardous environment, Division2/Zone2.渔农处的最大的缺点是成本相对于其他方法。驱动器是最昂贵的使用，可能还需要具体的电机的设计被使用。基于驱动器的输出信号，过滤或未经过滤的，可能需要额外的电机结构特点。这些结构特征包括绝缘轴承，轴接地电刷和绝缘接头，由于潜在的轴从共模电压电流。如果没有这些功能，轴电流，循环通过轴的轴承，通过电机支架与背，创造，导致轴承过早失效的轴承弧，潜在的电弧时需要考虑应用电机/驱动封装在一个危险的环境中，第二册/区。An additional construction feature of a motor used on an AFD may require is an upgraded insulation system on the motor windings. An unfiltered output signal from a drive can create harmonic voltage spikes in the motor, stressing the insulation of the motor windings.It is important to note that the features described pertain to motors which will be startedand run on an AFD. If the drive is only used for starting the motor, these features may not be necessary.一种用在AFD电机的额外建筑功能可能需要的是升级的绝缘系统的电机绕组。从驱动一个未经过滤的输出信号可以在电机产生谐波电压尖峰，强调电机绕组绝缘。需要注意的是，所描述的功能涉及到的发动机将在该处跑起步很重要。如果驱动器是用于启动电机，这些特征可能是不必要的。Consult with the motor manufacturer for application specific requirements.随着应用程序的具体要求，电机制造商咨询。D. Primary Resistor or Reactor Starting 初级电阻或电抗起动This method uses either a series resistor or reactor bank to be placed in the circuit with the motor. Resistor starting is more frequently used for smaller motors.该方法利用一系列电阻器或电抗器的银行被放置在电路与电机。电阻起动更频繁地使用较小的电机。When the motor is started, the resistor bank limits the flow of inrush current and provides for a voltage drop at the motor terminals. The resistors can be selected to provide voltage reductions up to 50%. As the motor comes up to speed, it develops a counter EMF (electro-magnetic field) that opposes the voltage applied to the motor. This further limits the inrush currents. As the inrush current diminishes, so does te voltage drop across the