电梯结构及原理教案-8 电梯拖动系统.docVIP

8 电梯拖动系统 Lift driving system 电梯的电力拖动系统对电梯的起动加速、稳速运行、制动减速起着控制作用。拖动系统的优劣直接影响电梯的起动、制动加减速度、平层精度、乘坐的舒适感等指标。早期的电梯原动机都是直流电动机，在19世纪中叶之前，直流拖动是当时电梯唯一的电力拖动方式，19世纪末，电力系统出现了三相制交流电源，同时又发明了实用的交流感应电动机，因而从20世纪初开始交流电力拖动在电梯上得到了应用。 ling lift start-up speed, smooth operation and deceleration, electrical driving system plays a decisive role in such index as start-up, acceleration / deceleration, leveling accuracy and riding comfort. Before the middle of 19’s century, adopting DC motor, DC driving system was the only mode for lift; by the end of 19’s century, with the development of AC inductive motor, AC driving system was applied in lift from the beginning of 20’s century. 8-1 拖动系统分类 Driving system types 目前用于电梯的电力拖动系统有两大类，即：直流电梯拖动系统和交流电梯拖动系统。 直流电梯拖动系统通常分为二种：一是用发电机组构成的可控硅励磁的发电机-电动机驱动系统；二是可控硅直接供电的可控硅-电动机系统。 Currently, electrical driving system is classified into two types, i.e. DC driving system and AC driving system. DC driving system has two types, one is driven by controllable silicon excitation multiple dynamos – motor, the other by controllable silicon motor. 交流拖动系统又可分为三种：交流变极调速系统、交流变压调速系统和变频变压调速系统。 AC driving system includes three types: AC polar-speed-variable system, AC voltage-speed-variable system and frequency-voltage-speed-variable system. 8-2 直流拖动系统 DC driving system 直流电梯速度快、舒适感好、平层精度高。但由于其对电网的影响较大，所以在2m/s速度以下的电梯已不再应用，但目前在2m/s速度以上的电梯仍有应用（包括有齿轮的和无齿轮的）。 Featuring high running speed, good riding comfort and high leveling accuracy, DC lift has a great influence on electrical network, therefore, lift with speed of less than 2m/s is not out of use, but lift with speed of more than 2m/s is still in use (including geared and gearless). 直流电动机的转速可由下式表示： DC motor speed is indicated as follows: 8-1？？？？？？？ 式中Where: Ua — 电机进线端的电压Ua — Inlet voltage of motor Ia — 电枢电流Ia — Armature current Ra — 电枢电阻Ra — Armature resistance Rt — 外接调整电阻Rt — Varistor Ce — 电势常数Ce — Potential constant Φ — 励磁磁通Φ — Excitation flux 由上式可知，直流