異步電動機(jī)起動的方法和問題中英翻譯資料-資料下載頁
2025-05-12 02:39本頁面
【導(dǎo)讀】可選擇的如全壓啟動、降。壓啟動、自耦變壓器啟動、星三角轉(zhuǎn)換啟動、軟啟動、或者使用可調(diào)速驅(qū)動器，都有潛在優(yōu)勢和選擇。降壓啟動可以減小啟動轉(zhuǎn)矩，可以防止損壞負(fù)載。電容器的嚴(yán)重?fù)p壞。啟動負(fù)載以確保電機(jī)達(dá)到所需性能且成本最少。本文將探討最常見的幾種啟動方。法以及它們的應(yīng)用。降壓啟動包括固態(tài)啟動器、變頻啟動和自耦變壓器啟動。來說，在機(jī)械特性曲線上集中有三點(diǎn)。第二點(diǎn)是最小啟動轉(zhuǎn)矩，使電機(jī)由靜止加速到出現(xiàn)制動轉(zhuǎn)。矩是的最小轉(zhuǎn)矩。允許電動機(jī)產(chǎn)生最大的啟動轉(zhuǎn)矩使加速時(shí)間最短。電壓下降會使此電動機(jī)的啟動轉(zhuǎn)矩和工作在同一母線上的電動機(jī)的轉(zhuǎn)。的大幅下降，工作在此供電系統(tǒng)的電動機(jī)可能停車。作在低電壓下，第二個(gè)全壓啟動時(shí)電壓問題會使正在運(yùn)行的電機(jī)離線。電機(jī)啟動產(chǎn)生的力矩，甚至?xí)斐蔀?zāi)難性故障。這表明該系統(tǒng)的時(shí)間常數(shù)較大。時(shí)用星形連接時(shí)電壓降為原來的1/3，啟動電流和啟動力矩下降2/3。
【正文】 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. 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 mon 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. 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 started and run on an AFD. If the drive is only used for starting the motor, these features may not be necessary. Consult with the motor manufacturer for application specific requirements. D. Primary Resistor or Reactor Starting 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. 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 es up to speed, it develops a counter EMF (electromagic 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 resistor bank allowing the torque generated by the motor to increase. At a predetermined time a device will short across the resistors and open the starting contactor effectively removing the resistor bank from the circuit. This provides for a closed transition and eliminates the concerns due to switching transients. Reactors will tend to oppose any sudden changes in current and therefore act to limit the current during starting. They will remain shorted after starting and provide a closed transition to line voltage. IV. INCREMENT TYPE The first starting types that we have discussed have deal with the way the energy is applied to the motor. The next type deals with different ways the motor can be physically changed to deal with starting issues. Part Winding With this method the stator of the motor is designed in such a way that it is made up of two separate windings. The most mon method is known as the half winding method. As the name suggests, the stator is made up of two identical balanced windings. A special starter is configured so that full voltage can be applied to one half of the winding, and then after a short delay, to the second half. This method can reduce the starting current by 50 to 60%, but also the starting torque. One drawback to this method is that the motor heating on the first step of the operation is greater than that normally encountered on acrosstheline start. Therefore the elapsed time on the first step of the part winding start should be minimized. This method also increases the magic noise of the motor during the first step.
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