基于PLC的电机软起动控制

摘要

交流异步电动机由于结构简单、维护方便、价格便宜，广泛地作为电气传动主要的原动力。在电机的起动控制中，我们常用的有全压直接起动和降压起动两种方式。近年来，由于变频及软起动技术的发展，解决了电机控制中存在的一些难题，特别是软起动技术在解决大、中容量的电机起动问题中有着卓越的功能，可以说是替代传统起动方式，是降压起动的一项新技术。在直接起动方式下，起动电流是额定电流的4～7倍，起动转矩是额定转矩的0.5～1.5倍。这些特点使得电动机带负载起动的能力下降，容易发生过载损坏。同时过大的起动电流也会给供电电网带来很大的电流冲击，影响电网的其他用电设备的正常运行。因此，为提高电动机与电网的运行质量，经常采用软起动器装置来改善电动机的起动性能。

在现场的实时监控时，PLC 往往有一些多余的输入和输出点可以利用，因此越来越多的工业控制系统采用PLC作为控制核心。本文介绍一种基于PLC的电动机的软起动器的硬件和软件结构，这样就可以在原有的控制系统的基础上自行设计一个高性能的软起动器。

关键词：异步电动机，软起动器，电动机起动特性，PLC控制

Abstract

Ac induction motor is simple in structure, convenient in maintenance due, cheap price, widely as electrical transmission main driving force. Starting in motor control, we are full of direct starting and step-down start in two ways. In recent years, due to the frequency and soft starter, solve the technical development of motor control of some problems, particularly soft starter, in solving technical problems of motor starter capacity has excellent function, can say is to replace the traditional way, is starting a step-down start of new technology. In direct starting mode, starting current is rated current of the 4～7 times, starting torque is rated torque of 0.5～1.5 times. These characteristics make motor starting with load capacity, easy occurrence overload damage. While big starting current power grid will also give a current of electricity and other normal operation of the equipment. Therefore, in order to improve the quality of electric motors and operation, often use soft starter device to improve the performance of motor starter.

In the field of the real-time monitoring, PLC tend to have some extra input and output point can use, so more and more of the industrial control system, PLC as control core. This paper describes a method based on PLC motor soft starter of the hardware and software structure, which can in the original control system based on the design of a high-performance soft starter.

Key Words: induction motor，soft starter，motor starting characteristics，PLC control

目录

摘要........................................................... I Abstract.......................................................... II 1 绪论 (1)

1.1 课程研究的目的意义 (1)

1.2 相关技术国内外研究现状 (1)

1.3 本文主要研究内容 (1)

2 电机软起动的基本原理及控制方案研究 (3)

2.1 异步电动机传统起动方式 (3)

2.1.1 直接起动 (3)

2.1.2 定子串电阻或电抗减压起动 (3)

2.1.3 星形-三角形转换减压起动 (3)

2.1.4 自耦变压器减压起动 (3)

2.2 异步电动机软起动方式 (4)

2.2.1 限流软起动 (4)

2.2.2 电压双斜坡软起动 (5)

2.2.3 突跳软起动 (5)

2.3 软起动技术的优点 (6)

2.4 三相异步电动机的等效电路 (7)

2.5 系统总体设计 (9)

2.5.1 电动机软起动原理分析 (9)

2.5.2 电动机软起动方式与控制策略 (10)

3 软起动控制器硬件设计 (12)

3.1 主电路的设计 (12)

3.2 控制电路硬件设计 (15)

3.2.1 主控制器的选择 (15)