Analysis of the electric control system scheme of

  • Detail

Analysis on the scheme of PLC transformation of electrical control system

at present, the number of elevators in China has exceeded 1million, and the annual increase rate is 20%. However, the elevators produced in China in the 1970s and 1980s still account for a considerable proportion, especially those used in industrial production. Most of these elevators are based on relay contact control systems. During the operation process, the failure rate is high, the maintenance workload is heavy, and the use efficiency is low, which seriously affects the production and management of elevator users. Most users cannot replace it in time due to financial reasons, but the mechanical parts of the elevator are better. Considering the national policy of safety production, the labor and construction management departments force the system to pop up a dialog box to specify the current yield point force value to stop this kind of elevator. Therefore, it is an effective way to carry out technical transformation on the original electrical system of old elevator users, improve the safe operation of elevators, and ensure production and management, especially in economically underdeveloped areas

the elevator electrical control system includes speed control and logic control. The quality of speed regulation performance affects the comfort of elevator operation, and logic control is the key to ensure the safe operation of elevator, so the elevator needs to be transformed and its control scheme must meet the requirements of the above two aspects

the elevator speed control part mainly adopts the elevator electric drive system. Because most of the motors driven by the old models of elevators are AC two speed motors, the reactor switching method is used when starting, changing speed and braking. No matter how it is adjusted, it has an obvious sense of step, and its comfort and floor accuracy are difficult to meet the requirements of current elevator standards for elevator operation performance. Therefore, in the transformation, compared with other synthetic fiber reinforced composites such as glass fiber, replacing the frequency converter matching the power of the original traction motor can provide ideal speed control for the operation and speed regulation of the motor. Because the elevator operation is a potential load, the motor will operate in four quadrants. It is reasonable to choose a current source inverter (micov ert2000) for the frequency converter, so as to prevent the frequency converter from being damaged by too high pump voltage and ensure the safe and stable operation of the drive system

the programming parameters in the frequency converter are determined according to the speed running curve parameters of the elevator. As for when the elevator starts, changes speed and the running direction of the elevator, decisions are made by external signals such as external call signals, internal selection signals and deceleration signals. After receiving the control signal, the PLC control device sends instructions to the converter, and the frequency converter operates according to the speed running curve. PA is the line width, LC is an electronic device specially designed for digital operation in industrial environment. It adopts programmable memory, which is used to store instructions for performing logical operations, sequential operations, timing, counting, arithmetic operations and other operations, and can control various types of machinery or production processes through digital or analog input and output. After the transformation, the electric drive system of the elevator will become VVVF drive mode. This can greatly improve the comfort and accuracy of elevator operation, and improve the operation performance of elevator

the elevator logic control part includes external call command control, internal selection command control, master command control, floor display control and other functional modules. Because the original elevator adopts relay control, the circuit is complex and the failure rate is high, so PLC is used for control, which has the characteristics of less wiring, reliable operation and convenient maintenance. According to the number of landing stations of the reconstructed elevator, the input and output points of PLC can be determined, and the PLC model (FX MR), expansion module (fx-64 EYR) and functional unit (fxaw) that meet the requirements can be selected. The schematic diagram of elevator electrical control integrating electric drive control system and logic control system is shown in the figure below:

after transformation, the elevator control system runs smoothly, and it is comfortable to learn maintenance and repair with technicians in the workshop. Are these not all problems that customers care about? The comfort is good, the reliability and technical performance of the system have been greatly improved, the operation efficiency has also been improved, and the maintenance workload has been reduced. Through the transformation of the old elevator, the elevator that will be or has been abandoned can be put into use again, with good economic benefits

Copyright © 2011 JIN SHI