Fujifilm inverter - the application of inverter energy-saving technology in coal mines

As we all know, coal enterprises are large consumers of electricity, and their electricity consumption costs account for a considerable proportion of their production costs. In coal mining enterprises, due to the fact that the production equipment generally meets the characteristics of long service life, the phenomenon of large horse-drawn trolleys caused by large model selection, serious waste of electric energy, and the operation efficiency of equipment is often relatively low.

According to the survey, the electricity consumption of fans, pumps, compressors, hoisting winches, and gas extraction equipment accounts for more than 40% of the electricity consumption of the entire coal mine production. But a large part of the electricity is wasted. If the baffle and valve are used to adjust, it often causes a relatively large waste, and the motor frequency conversion speed regulation is used to adjust the flow, which can save about 20%-50%, which may naturally produce huge social and economic effects. For large-load motors, the starting time is often long, the current is large, and the insulation strength of the equipment is seriously affected, and it is easy to burn the high-power motor. And when starting, the impact on some mechanical equipment is greater, which often causes more serious mechanical damage.

Therefore, this not only increases the cost of equipment maintenance, but also has a great impact on the safety of the power grid. The control process is single, and the real-time performance is poor, and the degree of automation is low. At the same time, there are obvious defects in torque limit control, reversible operation control, speed control, start and stop mode, acceleration and deceleration function and service life of mechanical transmission parts, etc., which cannot meet the requirements of large-scale automatic control, and the development of frequency conversion speed regulation technology has become one of the good solutions to this problem.

Second, the principle and energy-saving effect of frequency conversion speed regulation technology

1. The principle of frequency conversion speed regulation technology

AC variable frequency speed regulation is a new technology developed in recent decades, which is recognized as a promising speed regulation method for its excellent speed regulation performance, significant power-saving effect and wide applicability in various fields of the national economy. The basic principle is that under the on-off action of power semiconductor devices, the power frequency AC voltage is changed to DC voltage through the rectifier bridge, and then converted by the inverter to the AC voltage with adjustable frequency and voltage as the driving power supply of the AC motor, so that the motor can obtain the voltage and current required for stepless speed regulation, which is one of the efficient speed regulation methods without additional slip loss.

On the basis of comprehensive strong and weak electric hybrid, mechatronic integration, comprehensive application of power electronics technology, micro technology and motor drive technology, which is AC frequency conversion speed regulation technology. In this way, it can be used as an efficient speed regulation method without additional slip loss, and at the same time, the motor can obtain the voltage and current required for stepless speed regulation. The variable frequency speed regulation technology developed in the energy crisis can effectively and greatly improve the work efficiency, because it can automatically smooth the speed increase and deceleration according to the motor load. In this way, through the change of the power supply frequency of the motor, as a high-efficiency, high-performance speed regulation means, the frequency conversion speed regulation technology can be effectively adjusted.

2. The energy-saving effect of frequency conversion speed regulation technology

With the rapid development of electronic technology, computer technology, automatic control technology and high-power output technology, AC motor frequency conversion speed regulation technology has made breakthrough progress, which has become a major means to save electricity, improve the environment and promote technological progress, and has become an inevitable development trend. The obvious energy-saving effect and superior regulation performance make the frequency conversion energy-saving technology more and more widely used in China's coal mines, and the technology is becoming more and more mature. Large-capacity, multi-functional, high-reliability inverters have been widely promoted and applied in coal mine production, saving a lot of electrical energy for coal mines, especially in fluid loads, with an energy-saving rate of 20%-60%. The principle of frequency conversion control is: the use of frequency conversion speed regulation motor to achieve real soft start and smooth speed regulation, the use of frequency converter control to improve the power factor of the input power supply, below the fundamental frequency for the constant torque output, the output power with the speed change.

3. The specific application of frequency conversion speed regulation technology in coal mine production - taking belt conveyor as an example

1. Energy-saving problems of belt conveyor in coal mine production

Belt conveyors are widely used as the main equipment for coal mine transportation, and with the development of high-yield and high-efficiency working faces in coal mines, more and more long-distance, large-volume, and high-speed belt conveyors are designed, manufactured and put into operation. The use of these large-scale models makes the problems of large impact load of the conveyor and the uneven output of the drive motor causing the motor overload more acutely exposed. The starting and operation mode of the belt conveyor is that the winding motor runs at power frequency after the rotor winding is depressurized and started, and then switched to the belt conveyor through the hydraulic coupler. The working principle of the belt conveyor is that the belt conveyor drives the belt through the drive hub, and the belt is driven by friction to move the belt on the support roller through tension deformation and friction. The belt is an elastic energy storage material, which stores a large amount of potential energy when the belt conveyor is stopped and running, which determines that the soft start method should be adopted when the belt conveyor starts.

Therefore, the following requirements are put forward for the starting and operation of the belt conveyor: if the motor is directly started with heavy load, the power supply is required to provide 6-7 times greater current than that of normal operation, so that the motor will be overheated and burned due to excessive current and long starting time; The power grid will affect the operation of other equipment due to the excessive reduction of voltage due to high current; Therefore, a new drive system is required to reduce the current when the motor is started. At present, large belt conveyors require the drive system to provide adjustable, smooth, and impact-free starting torque to reduce the impact, so as to improve the force on the whole machine, prolong the life of the whole machine, and improve the reliability of the equipment, that is, to achieve soft start. For long-distance belt conveyors, if the start is too fast, the tensioning device will not have time to tighten, which will make the transmission drum slip, resulting in heating and fire; For the upward conveyor with a large inclination angle, if the starting acceleration is too fast, it will cause the material to slide or roll the material; This requires controllable starting acceleration to achieve smooth starting. In order to facilitate the maintenance of the belt conveyor, it is hoped that the low-speed belt inspection operation can be realized.

To sum up, the drive system is required to be able to adapt to the requirements of starting, running and stopping conditions, so that the belt conveyor can start and stop smoothly, run efficiently, drive balanced, and work safely and reliably. However, at present, most domestic coal mines use hydraulic couplings to realize the soft start of the belt conveyor, and the mechanical efficiency of the hydraulic coupling is adjusted to zero when starting, so that the motor starts without load. Although the rotor series resistor is used to improve the starting torque and reduce the voltage and start at no load, the starting current of the motor is still very large, which will not only cause violent fluctuations in the grid voltage, but also cause mechanical shock and heating inside the motor. At the same time, due to the long-term work of the hydraulic coupler, the internal oil temperature will rise, the metal parts will be worn, the leakage and the efficiency will fluctuate, which will not only increase the difficulty and cost of maintenance, pollute the environment, but also make it difficult to solve the problem of power averaging and synchronization when multiple machines drive the same belt.

2. The application of frequency conversion speed regulation technology in belt conveyor

The automatic control system of frequency conversion speed regulation in the belt conveyor is composed of programmable controller PLC, frequency converter, current transformer, current transmitter, nuclear 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: the current transformer and the transmitter obtain the motor current signal. The speed signal collected by the speed sensor is converted into a voltage signal. The speed signal collected by the motor speed sensor is converted into a voltage signal. The nuclear belt scale collects the volume signal. Each signal is fed into the core module.

Control unit: When the PLC receives the detection signal, after judgment and decision-making, the starting, power balance, and energy-saving speed regulation functions of the belt conveyor are completed. At the same time, the main control unit also has fault protection functions such as belt breakage, coal stacking, belt tearing, smoke, slippage, and temperature.

Execution unit: The inverter receives the frequency control signal of the PLC, and adds the voltage of the corresponding frequency to the motor according to the given signal output, so as to realize the speed regulation of the motor and complete the various functions of the belt conveyor. After the transformation of frequency conversion technology, the belt conveyor has completely realized the soft start and soft stop operation mode of the belt conveyor, so that the belt conveyor has more stable performance in the work.

The power factor of the system reaches more than 0.9 in the whole process, which greatly saves reactive power. After the frequency converter is used, the total transmission efficiency of the system is 5%-10% higher than that of the fluid coupling drive. After the transformation, the system can automatically adjust the output frequency and output torque according to the load change, which changes the previous mode of constant speed operation of the motor at power frequency, and saves power energy consumption to a large extent. Moreover, the use of four-quadrant medium and high voltage inverter 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 coupling saves the maintenance and repair costs of the equipment greatly. It is more perfect in terms of energy conservation and environmental protection.

IV. Conclusion

In short, the application of frequency converter in coal mine has achieved good results, with the development of new power electronic devices and the continuous improvement of performance, the application of frequency conversion speed regulation technology in coal mine production will play a greater role and achieve more significant economic benefits.
Fujifilm inverter - the application of inverter energy-saving technology in coal mines

Fujifilm inverter - the application of inverter energy-saving technology in coal mines

Fujifilm inverter - the application of inverter energy-saving technology in coal mines

Sections viewed

Contact

working hours