基于PLC的可逆变三相异步电机调速系统程设计论文.docVIP

基础课程设计（论文） 基于PLC的可逆变三相异步电机调速系统 摘要 摘要 PAGE — — PAGE 17 摘要 近年来，随着科技的进步，直流电机得到了越来越广泛的应用，直流具有优良的调速特性，调速平滑，方便，调速范围广，过载能力强，能承受频繁的冲击负载，可实现频繁的无极快速起动、制动和反转，需要满足生产过程自动化系统各种不同的特殊要求，从而对直流电机提出了较高的要求，改变电枢回路电阻调速、改变电压调速等技术已远远不能满足现代科技的要求，这是通过PWM方式控制直流电机调速的方法就应运而生。 采取传统的调速系统主要有以下的缺陷：模拟电路容易随时间飘移，会产生一些不必要的热损耗，以及对噪声敏感等。而用PWM技术后，避免上述的缺点，实现了数字式控制模拟信号，可以大幅度减低成本和功耗。并且PWM调速系统开关频率较高，仅靠电枢电感的滤波作用就可以获得平滑的直流电流，低速特性好；同时，开关频率高，快响应特性好，动态抗干扰能力强，可获很宽的频带；开关元件只需工作在开关状态，主电路损耗小，装置的效率高，具有节约空间、经济好等特点。 本系统已STC89C52单片机为核心，通过内部定时器产生PWM波形，控制LN298大功率H桥路驱动直流电机已达到控制转速的目的。通过数码管将速度等级显示出来，此外可以通过按键控制电机的正传反转、以及电机速度加和减。 关键词：STC89C52;单片机；PWM调速；数码管显示；按键 ABSTRACT In recent years, with the progress of science and technology, the DC motor has been used more and more widely, DC has excellent speed characteristics, speed smooth, convenient, wide speed range, strong overload capacity, able to withstand the impact of frequent load, extremely fast starting, braking and reverse can be realized without frequent, need to meet the specific requirements of various the production process automation system is different, so as to put forward a higher request to the DC motor, the armature circuit resistance speed change, to change the voltage control technique cant meet the requirements of modern science and technology, it is through the PWM mode control DC motor speed will emerge as the times require. Take the traditional speed regulation system mainly has the following defects: analog circuit is easy to drift over time, will produce some unnecessary heat loss, and sensitive to noise. Using PWM technology, to avoid the disadvantages, realization of the digital control of analog signal, can greatly reduce the cost and power consumption. And the higher switching frequency PWM speed control system, filtering effect can be obtained by armature inductance DC current smooth, good low-speed performance; at the same time, high switching frequency, fast dynamic response characteristics of a good, strong anti-interference ability, c