Application of frequency converter in hot rolling bar line mill

1. Introduction

With the dual pressure of energy conservation and emission reduction and production costs, today's steel industry needs higher efficiency than ever before. For any steel plant, a highly reliable and cost-effective transmission product can improve productivity and production capacity as well as the reliable operation time of equipment, shorten downtime, and reduce costs and logistics time.

2. INVT Engineering Transmission Solution

In the past five years, INVT variable frequency transmission products have been increasingly used in domestic steel enterprises. INVT has appeared in more and more key links of the same enterprise. INVT transmission products provide complete and reliable solutions for steel enterprises. The following are the main solutions currently available:

1) Rolling mill variable frequency drive system solution for hot rolling bar and wire production line

2) Frequency conversion tension winding and unwinding control solution for reversible cold rolling mill

3) Multi-motor control system solution for roller conveyors

4) Frequency conversion control system solutions for metallurgical cranes

5) High-voltage variable frequency drive system solutions for dust removal fans, blast furnace fans, etc.

Next, we will introduce the application of INVT Goodrive800 series engineering drives in domestic hot rolling bar mills and high-speed wire mill drives.

2.1 Hot rolling bar mill

2.1.1 Application Background

AC rolling line has become a trend. In order to optimize product structure, improve production efficiency and process level, reduce energy consumption, and enhance existing production capacity and product performance, a domestic company has built a new AC system bar production line. The transmission system adopts a multi-drive system consisting of a rectifier feedback unit + a public DC bus segment + an inverter unit. The main rolling mill uses the INVT GD800 series as the core main drive, combined with the Siemens S7-400 to form a complete control drive system.

2.1.2 Introduction

The entire rolling line system adopts network control, the process control level adopts industrial Ethernet, and the basic automation level adopts Profibus-DP fieldbus. The entire rolling line adopts Siemens S7-400CPU master control with up to 10 remote I/O stations, and implements two-level computer control. The process control level completes the full-line speed setting, rolling program storage, full-line rolling piece tracking, report printing, etc.; the basic automation level completes the full-line speed cascade control, rough, medium and fine rolling micro-tension control, flying shear shear control, looper control, etc.

2.1.3 Rolling mill transmission configuration

2.1.4 Main control system network diagram

2.1.5 System Features

1) The system has good compatibility and stability, safe, practical and reliable

2) Adopt high-power module parallel connection technology, easy power expansion and good maintainability

3) Compared with DC drive system, it can save more than 4% energy

4) High dynamic and static response speed

5) Use pulse encoder feedback vector control to ensure accurate speed control

6) Efficient harmonic suppression and noise reduction functions

7) Real-time detection and diagnosis to ensure safe and continuous operation of the system

2.2 Hot rolling high-speed wire mill

2.2.1 Application Background

In order to optimize product structure and improve existing production capacity and product performance, a domestic enterprise built a new AC system high-speed wire production line. The customer required a new wire plant at the most optimized cost, which could improve product quality and production efficiency, reduce energy demand, reduce downtime, and reduce the cost per ton of steel, while having higher reliability and lower maintenance costs.

2.2.2 Solution Architecture

1) The rolling line main console centrally controls and monitors the entire high-speed line through the operating console and the host computer

2) According to the capacity and process, the main rolling mill drive adopts the control method of rectifier feedback unit + public DC bus + inverter unit combination

3) The system adopts network control, the process control level adopts industrial Ethernet, and the basic automation level adopts Profibus-DP fieldbus

2.2.3 Main features

1) Improve the utilization efficiency of existing assets and equipment, economical cost, and improve product quality and process control

2) Based on Profibus-DP transmission control network, networked fast communication can easily connect to the upper automation system

3) Based on the common DC bus solution composed of Goodrive800 inverter and rectifier feedback unit, reduce energy consumption

4) Specially designed for the special requirements of the metallurgical industry, with extremely high operating reliability

5) Bidirectional energy flow, low harmonics

6) Adopt modular technology to minimize the complexity of the system and shorten the installation and debugging time

7) The whole module parallel power expansion technology makes the system power easy to expand

8) Professional local support team and preventive maintenance services ensure high availability of the system

3. Overview

Relying on its own accumulated technical advantages and grasp of details, INVT's Goodrive800 AC drive system uses high-performance vector control technology and stable function rate adaptive Profibus-DP network support, and cooperates with Siemens PLC to achieve high-precision control of large dynamic load changes in high-speed wire and bar main rolling mill drives. It is a successful attempt of domestic inverters on steel rolling production lines. Its core control and power unit have been proven to be stable and reliable in practice, winning praise and recognition from customers.