INDUCTION MOTOR STARTING METHODS AND ISSUES感應電動機的起動方法和問題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： 許多方法可用于啟動大型交流感應電動機。選擇如全電壓，通過自耦變壓器或Y形三角電壓降低，軟起動器，或可調速驅動器的使用都可以有潛在的優勢和權衡。降壓起動可以降低起動轉矩，防止損壞負載。此外，校正電容器可用于降低功率因數，但必須注意正確的尺寸。錯誤的電容器的使用可能會導致重大損失。選擇適當的啟動方法，電機將包括為保證電機的設計提供了所需的性能的同時，最大限度地降低其成本的初始荷載的動力系統分析。本文將最常用的起動方法和推薦的應用研究。Index Terms: motor starting. Reduced voltage start auto transformer, wyes-delta, power factor correction索引條款：電動機起動。降壓起動自耦變壓器，Y形三角洲，功率因數校正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.簡介：有起動異步電動機的幾種常見方法：全電壓，降低電壓，Y形三角洲，和部分繞組類型。低電壓型可包括固態啟動器，變頻驅動器，和自耦變壓器。這些，連同全電壓，或直接起動，給買方的汽車種類繁多的時候指定在給定的應用程序中使用的電機。每種方法都有其自身的利益，以及性能的權衡。正確的選擇會涉及的任何權力制約制度進行徹底的調查，以加速負載設備的整體成本。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.為了使負載能加速，電機必須產生更大的扭矩比負荷要求。一般有三點對電機轉速的扭矩曲線的興趣。第一個是鎖定轉子扭矩（LRT），最小轉矩，電機將在剩下的所有的角位置的轉子。二是拉轉矩（放），定義為最小轉矩由電動機在加速期從其余的速度，轉矩發生。最后是擊穿扭矩（BDT）被定義為最大轉矩，電機的發展。如果這些點所需的負荷曲線的下方，然后電機不能啟動。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.這需要對電機的加速負載的時間是依賴于負載的慣量和電動機的轉矩與負載曲線之間的邊緣，有時也被稱為加速轉矩。一般來說，越需要電機的加速負載時，其會在轉子產生更多的熱量，短路環和定子繞組。這種熱導致這些部件的附加應力，可以有一個影響電機的壽命。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。全壓全電壓起動方法，也被稱為直接起動，是采用最簡單的方法，具有最低的設備成本，是最可靠的。該方法利用一控制關閉接觸器應用全電壓的電機端子。這種方法將使電機產生最高的起動轉矩和提供最短的加速時間。這種方法也提出了最高的菌株對電力系統由于高的起動電流，一般可以在六到七倍的電機電流正常滿負荷。如果電機是電力系統薄弱，突然的高功耗可引起電壓暫降，不僅在電機端子，但整個電源總線送起動電機。此電壓下降將導致電機的起動轉矩下降，下降和轉矩的任何其他電機電源總線上運行。開發的感應電動機的轉矩變化大致為所施加的電壓的平方。因此，根據電壓下降量，電機在這一弱勢客車運行可能失速。此外，電壓條件下監測許多控制系統，一個潛在的問題，可以采取離線運行電動機全電壓起動時。除了電源總線的電性變化，一個潛在的直接起動的物理缺點的驅動設備，看到突然加載。這種沖擊加載由于暫態扭矩可超過600%的鎖定轉子扭矩可增加對設備的磨損，甚至導致災難性的故障，如果負載不能處理在盯著由電機產生的轉矩。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：電容起動異步電動機通常有非常低的功率因數在起動和結果具有非常大的功畫。見圖2。這對系統的影響可以通過增加電容器的電機起動時降低。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.大反應電流的電機滯后電壓90電角度的要求。這無功不產生任何可測量的輸出，而是用于電機的功能所需的能量。應用系統的電壓的乘積這功分量可測變量（乏）。電容器的行為提供一電流，使電壓90電角度。領先的電流由電容器提供取消滯后電流通過電機的要求，減少需要從電力系統繪制功量。為了避免過電壓和電機損壞，須特別小心，以確保電容器作為電機達到額定轉速的刪除，或在斷電時使電機不會從電容器提供勵磁電流，發電機模式。這將擴大對下一節和附錄中。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.功率因數校正電容器還可以留下永久連接到提高全負荷功率因數。當以這種方式使用它們被稱為功率因數校正電容器。電容器不應尺寸大于磁化電流的電機除非他們可以斷開電機在斷電的情況下。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.另外的電容器將改變有效開路時間常數的電機。時間常數表明剩余電壓在電機額定電壓衰減到36.8%的功率損失后所需的時間。這通常是一個三秒的無電容器。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 .與連接到電機的引線電容器，電容器可以在電動機的電源已斷開，繼續提供磁化電流。這是一個較長的時間常數為系統顯示。如果電機是驅動大慣性負載，電機可以改變與勵磁發電機行動。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.從電容器和軸驅動的負載電流。這可能會導致在電機端子實際上在上升至近50%，在某些情況下，額定電壓在電壓。如果重新連接電源之前，這個電壓衰減嚴重的瞬變可以創建可引起明顯的開關電流和扭矩，會嚴重損壞電機和驅動設備。這種現象的一個例子是在附錄中列出了。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。降低電壓的電壓降低的方法的目的是降低電機起動電流對電力系統的電壓控制，電機將在終端。這是了解負載的特點是啟動時考慮任何形式的降壓起動很重要。汽車制造商將需要轉速扭矩曲線和驅動設備的慣性，當他們驗證他們的設計。該曲線可由初始，或脫離扭矩，只有其他四個數據點的速度范圍內，和全轉速轉矩的起動條件。離心式或平方曲線可以在許多情況下，假設，但也有一些應用，這將是有問題的。一個例子是，螺桿壓縮機具有更高的扭矩要求在較低的速度比一般離心泵或風機負載。見圖3。通過了解負載的細節必須開始制造商可以確保電機能產生足夠的轉矩啟動負載，具有起動方法，chhosen。A. Autotransformer 答：自耦變壓器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電機引線連接到變壓器的低壓側。這是最常用的水龍頭80%，65%，和50%。在50%上的電壓電流是25%次全電壓鎖定轉子電流。電機啟動這個降低的電壓，然后在一個預先設定的條件達到連接切換到線電壓。這種情況可能是一個預先設定的時間，目前的水平，總線伏，或電機速度。的變化可在一個閉合電路的過渡，還是一個開放的電路轉換的方法。在開放電路電壓的連接方法是作為它是從低電壓變為水平線。護理應用于確保不會有問題，從瞬變由于開關。這個潛在的問題可以通過使用閉路過渡消除。與閉回路法有一個連續的Voltage applied to the motor. Another benefit with the autotransformer starting is in possible lower vibration and noise levels during starting.施加到電動機的電壓。在啟動過程中的另一個好處與自耦變壓器起動在盡可能低的振動和噪音水平。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.由于電機產生的轉矩會隨著所施加的電壓的平方變化，要特別注意確保有足夠的加速轉矩可以從電機。用于驅動設備，隨著慣性力矩速度曲線可以用來驗證電機設計。一個好的經驗法則是有一個最低的額定滿負載轉矩的電動機10%作為所有點的曲線邊緣。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，加速時間應進行評估，以確保電機由于較長的加速時間產生足夠的熱容量的熱處理。B. Solid State or Soft Starters B.固態軟起動器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.這些器件采用可控硅整流器或疤痕。通過控制觸發角的晶閘管電壓，該裝置產生可控制的電動機起動過程中通過限制只有正弦波的時間部分功率流。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.軟起動器使用最廣泛的類型是類型的電流限制。電流限制為175%到500%的滿負荷電流編程的裝置。然后它會增加電機電壓直至達到極限值，然后就認為，電流為電動機的加速。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.轉速表能與固態起動器用于控制加速時間。輸出電壓是由起動器必須提供一個恒定的速率加速調整。在以相同的預防措施，啟動轉矩應遵循的軟起動器與其他降壓起動方法。由于可控硅的觸發角的另一個問題是，電機能經歷諧波振蕩的扭矩。根據驅動設備，這可能會導致令人興奮的系統的自然頻率。 C. Adjustable Frequency Drives C.變頻驅動器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.這種類型的設備提供了最大的整體控制和靈活性，在起動異步電動機給最轉矩電流量。它也是最昂貴的。驅動的變化不僅電壓水平，而且頻率，使電機在一個恒定的伏特每赫茲級操作。這使電機產生滿負載轉矩在整個調速范圍大，可達10:1。在啟動過程中，額定電流的150%是典型的。這允許啟動所需的負載功率的顯著減少，并降低了電機產生的熱量，所有這些總計達更高的效率。漁農處的使用也可以允許一個較小的電機是由于可用的扭矩在較低的速度范圍內顯著增加的應用。電機仍應尺寸大于所需的功率來驅動負載。漁農處允許的負荷，是不是加速容易獲得與其他類型的降壓起動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.漁農處的最大的缺點是成本相對于其他方法。驅動器是最昂貴的使用，可能還需要具體的電機的設計被使用。基于驅動器的輸出信號，過濾或未經過濾的，可能需要額外的電機結構特點。這些結構特征包括絕緣軸承，軸接地電刷和絕緣接頭，由于潛在的軸從共模電壓電流。如果沒有這些功能，軸電流，循環通過軸的軸承，通過電機支架與背，創造，導致軸承過早失效的軸承弧，潛在的電弧時需要考慮應用電機/驅動封裝在一個危險的環境中，第二冊/區。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.一種用在AFD電機的額外建筑功能可能需要的是升級的絕緣系統的電機繞組。從驅動一個未經過濾的輸出信號可以在電機產生諧波電壓尖峰，強調電機繞組絕緣。需要注意的是，所描述的功能涉及到的發動機將在該處跑起步很重要。如果驅動器是用于啟動電機，這些特征可能是不必要的。Consult with the motor manufacturer for application specific requirements.隨著應用程序的具體要求，電機制造商咨詢。D. Primary Resistor or Reactor Starting 初級電阻或電抗起動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.該方法利用一系列電阻器或電抗器的銀行被放置在電路與電機。電阻起動更頻繁地使用較小的電機。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