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鞍山科技大学本科生毕业设计（论文） 第 I 页

PLC与变频器结合实现电动机恒转矩控制

摘要

本文介绍了一种由西门子PLC和变频器构成的恒转矩控制系统.采用PROFIBUS协议实现了PLC与变频器的通讯. 介绍PROFIBUS通信协议,以德国西门子公司MICROMASTER 440型变频器为例,介绍了PLC与变频器进行通信的硬件连接。依据该协议,实现了以PLC作为控制器,在PLC环境下编制程序对变频器进行远程控制.该系统可以对各变频器的运行参数进行在线监测,并进行远程控制。

文中介绍了关于钢板的清洗工艺,以系统的实际应用来说明本系统的实际价值，调节刷辊的转矩来控制对钢板的刷洗力度。最后附以程序,有PLC和变频器的通讯的程序和PLC与变频器结合控制电动机恒转矩的PLC程序. 实践证明,该系统能有效地减少系统布线、提高系统的抗干扰能力,为恒转矩控制系统提供了一个低成本和高性能的方案。

关键词：PLC，变频器，PROFIBUS协议

鞍山科技大学本科生毕业设计（论文） 第 II 页

PLC Combining With Frequency-converter Achieving Constant

Torque Control Of Electric Motor

Abstract

This paper introduces a control system for instance torque composed of SIEMENS PLC and frequency-converter. The serial communication between PLC and frequency-converter is realized based on the PROFIBUS protocol. The PROFIBUS protocol is introduced in detail. Hardware link of communication between PLC and frequency-converter are introduced with an example of SIEMENS

frequency-converter MICROMASTER 440. According to this protocol, remote control of inverter is

realized with SIEMENS PLC being controller under the environment of visual PLC. The presented system is very convenient to monitor the parameters of every frequency-converter on line and realize the distance control.

The paper introduced steel cleaning processes for the system to illustrate the practical application of the actual value of the system, Adjusting brush roller torque to control brush roller intensity on the skin of steel. At last, together with procedures, there are communication procedures of PLC and

frequency-converter and the procedures of PLC combining with frequency-converter achieving constant

torque control of electric motor. Practice has proved that the method can reduce electric connections and improve the anti-jamming capability of the system. Thereby a scheme for PLC combining with frequency-converter to achieve constant torque control of electric motor with low-cost and high-performance is provided.

Keyword: PLC，frequency-converter，PROFIBUS protocol

鞍山科技大学本科生毕业设计（论文） 第 III 页

目录

摘要 ...................................................................... I ABSTRACT ................................................................. II 1 绪论 .................................................................... 1 1.1 选题的背景 ..................................................................................................................... 1 1.2 PLC和变频器的发展 ..................................................................................................... 1 1.3 系统综述 ......................................................................................................................... 2 2 三相异步电动机 .......................................................... 4 2.1 异步电动机的旋转原理 ................................................................................................. 4 2.2 异步电动机的电磁转矩 ................................................................................................. 4 2.3 异步电动机的机械特性 ................................................................................................. 5 3 变频器的恒转矩控制 ...................................................... 6 3.1 变频器的工作原理 ......................................................................................................... 6 3.2 转矩控制时的运行特点 ................................................................................................. 6 3.3 转矩给定信号与电动机转矩 ......................................................................................... 6 4 STEP7-300简介 ......................................................... 8 4.1 PLC的定义 .................................................................................................................... 8 4.2 STEP7-300软件 .............................................................................................................. 8 5 分布式外围设备现场总线（PROFIBUS-DP） ................................... 9 5.1 PROFIBUS-DP简介 ...................................................................................................... 9 5.2 PROFIBUS-DP的物理连接 .......................................................................................... 9 5.3 PROFIBUS-DP的报文结构 .......................................................................................... 9 6 系统的实现 ............................................................. 11 6.1 系统的硬件连接 ........................................................................................................... 11 6.2 MICROMASTER 440标准型变频器设置 .................................................................. 11