1、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 advant
2、ages 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 dam
3、age. 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 recommen
4、ded 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
5、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
6、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. Pro
7、per 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
8、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 wi
9、ll 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 defin
10、ed 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
11、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, th
12、e 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
13、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 meth
14、od 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
15、 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 runnin
16、g 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 pote
17、ntial 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
18、 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
19、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，
20、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
21、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 s
22、ystem 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 t
23、he 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 m
24、ode 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
25、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
26、 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
27、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 th
28、e 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
29、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 volta
30、ge 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
