Coal enterprises are large power consumers, for coal mine production enterprises, the proportion of electricity consumption is quite large, according to the survey, the electricity consumption of fans, water pumps, compressors, lifting winches, gas pumping equipment accounts for more than 40% of the entire coal mine production electricity consumption. The development of variable frequency regulation technology can effectively solve the single control process, while real-time is poor, the degree of automation is low and other problems.
Application of frequency converter energy saving technology in coal mining industry
I. The principle and energy-saving role of frequency control technology
1, the principle of frequency control technology
AC frequency converter speed regulation is a new technology developed in recent decades, with its excellent speed regulation performance, remarkable power saving effect and wide applicability in various fields of the national economy, and is recognized as a promising way of speed regulation. AC frequency converter speed regulation technology is a comprehensive application of microcomputer technology, power electronics technology and motor transmission technology. The basic principle is that under the interruptive effect of power semiconductor devices, the working frequency AC voltage is converted to DC voltage by rectification bridge, and then converted from the inverter to the frequency, voltage adjustable AC voltage as the drive power of the AC motor, so that the electric motor obtains the voltage and current required for stepless speed regulation, is one of the efficient ways of speed regulation without additional displacement loss.
This can be used as a high-efficiency speed regulation method without additional displacement loss, at the same time, so that the electric motor obtains the voltage and current required for stepless speed regulation.
2, the energy-saving role of frequency control technology
With the rapid development of electronic technology, computer technology, automatic control technology, and high power output technology, AC motor frequency converter speed regulation technology has made breakthrough progress, becoming a major means of saving energy and improving the environment, and promoting technological progress, has become an inevitable development trend.
Specific applications of variable frequency control technology in coal mining production using belt conveyors as examples
1, belt conveyor in coal mine production energy saving problem
Belt conveyors are widely used as the main equipment of coal mine transportation, with the development of coal mine high productivity and efficient working surface, long-distance, large volume, high-speed belt conveyors are more and more designed, manufactured and put into operation. The use of these large machines, so that the conveyor has a large impact load, driving motor output uneven, leading to motor overload and other problems are more sharply exposed.
Therefore, the following requirements for the start and operation of the belt conveyor: if the motor is directly overloaded when starting, the power supply is required to provide 6-7 times more current than normal operation, so that the motor will be overheated due to excessive current and too long start-up time; The power grid will affect the operation of other equipment due to excessive voltage reduction due to large current; Therefore, the new type of drive system can reduce the current when the motor starts. Currently, large belt conveyors require the drive system to provide adjustable, smooth, non-impact starting torque to reduce the impact, thereby improving the force condition of the entire machine, extending the life of the entire machine, improving the reliability of the equipment, that is, to achieve soft start. Long-distance belt conveyors, if the start is too fast, the tightening device will not tighten, so that the transmission roller slips, resulting in heating fire; For large inclination belt conveyor, if the start acceleration is too fast, will cause material slip or rolling phenomenon; This requires controllable start-up acceleration to achieve smooth start-up. To facilitate the maintenance of belt conveyors, we hope to achieve low-speed test belt operation.
In summary, the drive system is required to be able to adapt to the requirements of starting, operating, and parking conditions, so that the belt conveyor starts and stops smoothly, runs efficiently, drives balance, and works safely. However, at present, most coal mines in China use hydraulic couplers to achieve soft start of belt machines, adjusting the mechanical efficiency of the hydraulic coupler to zero at start-up, so that the motor starts unloaded.
2, frequency control technology in belt conveyor applications
The frequency control automatic control system in the belt conveyor consists of programmable controller PLC, frequency converter, current exchanger, current transmitter, nuclear belt scale, belt speed sensor and motor speed sensor, etc., which can be summarized into three parts of detection unit, control unit and execution unit.
Detection unit: The current sensor and transmitter acquire the motor current signal. The belt speed signal acquired by the belt speed sensor is converted to the voltage signal. The speed signal acquired by the motor speed sensor is converted to the voltage signal. The nuclear belt scale acquires the flow signal. Each signal is fed to the core module.
Control unit: When the PLC receives the detection signal, after judging the decision, complete the belt conveyor start, power balance, energy-saving speed adjustment function. At the same time, the main control unit also has breaking belt, coal stacking, tearing belt, smoke, slipping, temperature and other fault protection functions.
Execution unit: the frequency converter receives the frequency control signal of the PLC, according to the given signal output of the corresponding frequency of the voltage added to the motor, to achieve the motor speed adjustment, complete the various functions of the belt conveyor. After the conversion of frequency technology, the belt machine completely realizes the soft start and soft stop operation mode of the belt conveyor, so that the belt machine is more stable in performance.
After the conversion, the system can automatically adjust the output frequency and output torque according to the load change, changing the previous motor frequency constant speed operation pattern, greatly saving power energy consumption.
III. Conclusion
In summary, the application of frequency converters 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 converter speed control technology in coal mine production will play a greater role and achieve more significant economic benefits.