1. Introduction

The early paper-making machines used DC regulating control devices for their transmission systems. Most of these DC regulating devices were analog devices, which were difficult to debug, had poor stability and high failure rates. The brushes of DC motors were prone to wear, had a poor stability cycle, high failure rates, high maintenance costs, and low equipment efficiency. In the past 10 years, AC variable frequency speed control technology has matured. AC variable frequency speed control has replaced DC speed control as the development trend. This scheme takes a board paper machine manufactured in 1995, with separate drive shafts, as an example to briefly introduce the application of the FGI PM100M series vector control variable frequency converter in the replacement and renovation of old equipment.

2. Confronting problem

Our company's 1880mm wide board paper machine production line is a three-ring screen, two-stage press and three-drying cylinder paper machine manufactured in 1995. The original transmission mode was that three networks and two voltages shared one 100kW DC motor for transmission. The main shaft of the three-cylinder and the three sections of the calendering and paper winding machines is driven by a 100kW DC motor. Two sets of SIED900 DC drive devices and analog speed chains are used to form a division-sum shaft speed regulation and control system. Due to the long service life, system aging and mechanical mating fading, the difficulty of process control has increased. Unstable load often causes speed difference, frequent paper sheet breakage, decline in paper quality, low equipment efficiency, and both the DC control device and the DC motor are approaching the end of their service life.

3. Transformation ideas

Replace one of the DC motors with two AC motors for transmission, adjust the speed of the ordinary squirrel-cage motor, reconfigure the speed and current display on the on-site operation panel according to the output port of the frequency converter, and separate and connect the control cables for control. Based on the calculation of the actual load situation, plan to configure one FGI PM100M frequency converter and one Y-280M6/55kW motor.

4.Control requirement

The process control requirements should include both crawling/running two operating states. The crawling state is used for the preparation and adjustment stages of process output; the running state is the production state. The speed setting adopts the multi-stage speed increase MOP mode button for ascending and descending speed fine-tuning control with MOP reduction for saving, so that the switching and memory of crawling/running states can meet the process operation habits, and an emergency stop button is added to meet the safety requirements.

After confirming that the wiring is correct, disconnect the load, set the motor parameters according to the parameter setting table, perform the motor parameter rotational self-tuning, then set the corresponding parameters according to the control requirements, and start the machine for trial operation to test all functions. After the buttons comply with the design control requirements, use E3-30, 31; E3-32, 33 to display the current and speed parameters correction on ports A01, A02, and then it can be put into formal operation. When the control accuracy is required to be high, the speed regulator parameters can be adjusted and set according to the user manual to achieve satisfactory control effects.

5. Using effect

Although the existing system has been transformed into a hybrid system of AC variable frequency speed regulation and DC speed regulation, breaking the speed chain coupling, the disturbance caused by the front and rear regulation of the original speed chain has been eliminated, and it has been changed to a quasi-partial regulation mode. The speed control is smooth and flexible, and the operation is stable. At the same time, it eliminates the overload impact trip and zero start state caused by improper crawling/operation switching regulation of the DC control device. The paper breakage rate has decreased by 65% to 80%, equipment efficiency has significantly improved, and energy consumption has dropped by 8%. Cost performance: The system replacement and transformation including the motor and engineering frequency converter have been completed.

6. Expectation

The FGI PM100M series vector control frequency converter selected in this scheme is a major domestic brand. It has a complete range of high, medium and low application grade series and relatively comprehensive compatibility with major international famous brand machines.