Application of frequency converter energy saving technology in coal mining industry
Release Date: 2018-04-19 Source: Industrial Control China View: 21812
Core Tip: Coal enterprises are large consumers of electricity, for coal mine production enterprises, the proportion of electricity consumption is quite large, according to the survey, fans, pumps, compressors, hoisting winches, gas extraction equipment, electricity consumption accounts for more than 40% of the entire coal mine production electricity consumption. The development of frequency conversion speed control technology can effectively solve the single control process, while the real-time is poor, low degree of automation and other issues. First, the principle of frequency conversion speed control technology and energy saving 1, the principle of frequency conversion speed control technology AC frequency conversion speed control is a new technology developed in recent decades, with its speed performance, significant power saving effect and wide applicability in various fields of the national economy, and the
Coal enterprises are large consumers of electricity, for coal mine production enterprises, the proportion of electricity consumption is quite large, according to the survey, fans, pumps, compressors, hoisting winches, gas pumping equipment, electricity consumption accounts for more than 40% of the electricity consumption of the entire coal mine production. The development of frequency conversion speed control technology can effectively solve the single control process, while the real-time is poor, low degree of automation and other issues.
First, the principle of frequency conversion speed control technology and energy saving effect
1, the principle of frequency conversion speed control technology
AC frequency conversion speed control is a new technology developed in recent decades, which is recognized as a *promising* speed control method with its excellent speed control performance, significant power-saving effect and wide applicability in various fields of national economy. AC frequency conversion speed control technology is a comprehensive application of microcomputer technology, power electronics technology and motor drive technology. The basic principle is that under the on-off action of power semiconductor devices, the frequency AC voltage will be changed into DC voltage through rectifier bridge, and then converted into frequency and voltage adjustable AC voltage by inverter as the driving power supply of AC motor, so as to make the motor obtain the voltage and current required for stepless speed regulation, and it is a kind of high efficiency speed control with no additional It is one of the high-efficiency speed regulation methods without additional rotational loss.
On the basis of integrated strong and weak power mixing and electromechanical integration, power electronics, micro-technology and motor drive technology are comprehensively applied, which is AC frequency conversion speed control technology. This can be used as a high-efficiency speed control method without additional rotational loss, and at the same time, it makes the motor obtain the voltage and current required for stepless speed control. The frequency conversion speed control technology developed in the energy crisis can effectively and substantially improve the working efficiency because it can automatically and smoothly increase and decrease the speed according to the motor load. In this way, through the motor power supply frequency change, as a high-efficiency, high-performance means of speed control frequency conversion speed control technology can realize effective regulation.
2, the energy-saving effect of frequency conversion speed control technology
With the rapid development of electronic technology, computer technology, automatic control technology, high-power output technology, AC motor frequency conversion speed control technology has made breakthrough progress, become today's power saving and improve the environment, to promote technological progress of a major means, has become an inevitable development trend. Obvious energy-saving effect and superior regulation performance, so that the frequency conversion energy-saving technology in China's coal mines is more and more widely used, the technology is also more and more mature. Large-capacity, multi-functional, highly reliable frequency converter has been widely promoted and applied in coal mine production, saving a large amount of electricity for coal mines, especially in fluid loads, its energy saving rate is 20% to 60%. The principle of frequency conversion control is: using frequency conversion speed control motor to realize real soft start and smooth speed regulation, using frequency converter control to improve the power factor of the input power supply, in the base frequency below the constant torque output, the output power changes with the rotational speed.
Second, the specific application of frequency conversion speed control technology in coal mine production to the belt conveyor for example
1、Energy saving of belt conveyor in coal mine production
As the main equipment of coal mine transportation, belt conveyor is widely used. With the development of high-yield and high-efficiency working face in coal mine, more and more long-distance, large-capacity and high-speed belt conveyors are designed, manufactured and put into operation. The use of these large-scale machines makes the problems of large shock loads and uneven output of drive motors leading to motor overloads, which exist in conveyors, more sharply exposed. The starting and running mode of the belt conveyor is that the winding motor is started by the rotor winding voltage reduction and then operated at industrial frequency, and then switched to the belt conveyor by the hydraulic coupler. The working principle of the belt conveyor is that the belt conveyor moves by driving the hub and pulling the belt by friction, and the belt drives the object to move on the support roller through tension deformation and friction. The belt is an elastic energy storage material, and there is a large amount of potential energy stored when the belt conveyor stops and runs, which determines that a soft start should be used when the belt conveyor is started.
Therefore, the starting and operation of the belt conveyor puts forward the following requirements: if the motor is directly heavy load starting, the power supply is required to provide 6-7 times greater than the normal operation of the current, so that the motor will be due to excessive current and starting time is too long and overheating and burnt out; grid will be due to the high current so that the voltage is excessively lowered to affect the operation of other equipment; therefore, the requirements of a new type of drive system to reduce the current when the motor Therefore, a new drive system is required to reduce the current of the motor when starting. At present, large belt conveyor are required to drive the system can provide adjustable, smooth, impact-free starting torque to reduce the impact, thereby improving the stress on the machine, extend the life of the machine, improve equipment reliability, that is, in the hope of realizing the soft start. Long-distance belt conveyor, if the start too fast, the tensioning device will not be able to tighten, making the drive roller slippery, resulting in heat and fire; for large inclination angle of the upper transport belt conveyor, if the starting acceleration is too fast, will cause the material to slide down or roll the material phenomenon; this requires starting acceleration is controllable, to achieve a smooth start. In order to facilitate the maintenance of the belt conveyor, it is hoped that low-speed belt inspection operation can be realized.
In summary, the drive system is required to adapt to the requirements of starting, running and stopping conditions, so that the belt conveyor starts and stops smoothly, runs efficiently, drives a balanced, safe and reliable work. However, at present, most domestic coal mines use hydraulic coupler to realize the soft start of the belt conveyor, adjusting the mechanical efficiency of the hydraulic coupler to zero at startup, so that the motor starts with no load. Although the rotor series resistance to improve the starting torque and reduced voltage no-load start and other methods, but the motor starting current is still very large, not only will cause violent fluctuations in the grid voltage, but also cause the motor internal mechanical shock and heating and other phenomena. At the same time, due to the hydraulic coupler for a long time will cause its internal oil temperature, metal parts wear, leakage and efficiency fluctuations, etc., will not only increase the difficulty and cost of maintenance, pollution of the environment, but also make it difficult to solve the problem of power average and synchronization of more than one machine driving the same belt.
2、The application of frequency conversion technology in belt conveyor
Frequency control automatic control system in belt conveyor consists of programmable controller PLC, frequency converter, current transformer, current transmitter, nucleus belt scale, belt speed sensor and motor speed sensor, etc., which can be summarized into three parts: detection unit, control unit and execution unit.
Detection unit: current transformer and transmitter to obtain the motor current signal. Belt speed sensor to collect the belt speed signal, after conversion to voltage signal. The motor speed sensor collects the speed signal, which is converted into voltage signal. The core belt scale collects the transportation signal. Each signal is fed into the core module.
Control unit: when PLC receives the detection signal, after judgment and decision-making, it completes the function of starting, power balance and energy-saving speed regulation of the belt conveyor. At the same time, the main control unit also has fault protection functions such as belt breakage, coal stacking, belt tearing, smoke, skidding and temperature.
Execution unit: the frequency converter receives the frequency control signal from PLC, outputs the voltage of corresponding frequency to the motor according to the given signal, realizes the speed regulation of the motor, and completes various functions of the belt conveyor. After transformed by frequency conversion technology, the belt conveyor completely realizes the soft start and soft stop operation mode of the belt conveyor, which makes the belt conveyor more stable performance in work.
The power factor of the system reaches above 0.9 in the whole process, which greatly saves reactive power. The use of frequency converter drive, so that the total transfer efficiency of the system is 5% to 10% higher than the efficiency of the hydraulic coupling drive system efficiency. After the transformation, the system can automatically adjust the output frequency and output torque according to the load change situation, which changes the previous mode of constant speed operation of the motor's industrial frequency, and saves the power energy consumption to a large extent. Moreover, the use of four-quadrant high-voltage frequency converter realizes the energy feedback function of the belt conveyor, which further reduces the energy consumption of the belt conveyor, and the withdrawal of the hydraulic coupler greatly saves the maintenance and repair costs of the equipment. In energy saving and environmental protection is more perfect.
Third, conclusion
In short, the application of frequency converter in coal mines has achieved good results, with the development of new power electronic devices and the continuous improvement of performance, the application of frequency conversion technology in coal mine production will play a greater role, to achieve more significant economic benefits.