Chemical Engineering and Equipment About Frequency Control Technology Research and Application in Air Compressor Laijiang Zhen Changtian Enterprise Co., Ltd., Xiamen Xiamen 361026, the specific application method in the transformation, from principle to practice, the frequency control technology can be empty The intelligent control of the press contributes to energy saving.
1 Frequency Control Technology Overview Motor is an indispensable equipment in the production of various industries. The work of production machinery requires motor drag to achieve the set work. In the last century, due to the limitations of technological development, motor motion was basically a constant speed drag at a fixed speed. In an environment where the accuracy of control requirements is not high, constant speed operation can meet most of the production needs. With the industrialization and intelligent demand, the method of constant speed control and dragging has been unable to adapt to the production demand, and an adjustable space is proposed for the transmission mode. Therefore, the technology of intelligent speed regulation is gradually developing towards AC motors. In practice, the use of speed control technology can greatly improve the precision of machining, and can reduce labor intensity and improve production efficiency, and provide the necessary conditions for automated intelligent control. Specifically, the frequency conversion speed regulation technology is to use the frequency converter to drive the motor in the drag system to realize the adjustable speed, that is, let the motor work according to the established program or mode. However, regardless of whether the system adopts speed control technology, its stability is the biggest premise, that is, the system is required to automatically restore the function when it is subjected to external interference. The AC variable speed drive is mainly a variable frequency speed control drive for an AC motor using an electronic power conversion device. In addition to frequency control, there is another speed control method, such as variable pole speed stator variable speed speed regulation clutch speed regulation, etc., although these technologies can be applied in some occasions, but their performance can not be adjusted with the frequency conversion Speed ​​ratio.
The basic principle of the frequency conversion speed regulation is to change the synchronous frequency by changing the power supply frequency of the power supply, thereby changing the rotational speed of the motor. The highlight of the frequency conversion speed regulation is that the range is large, the speed is smooth, the efficiency is high, and the dynamic and static characteristics are excellent. It is the most widely used and excellent performance of the AC speed control mode. The electric machine is the existence of the moment of inertia of the system, and the rotation speed cannot be abruptly changed. However, changing the electrical parameters by external conditions will inevitably cause the electromagnetic torque to change, thereby destroying the original torque balance relationship, and a new system will be generated. Torque. In this case, the system will generate an acceleration that causes the system to accelerate or decelerate. When the external adjustment is stable, the system speed will reach equilibrium, and this process is the step-changer speed regulation process.
2 The application of frequency conversion speed regulation technology to the transformation of air compressor 2.1 The demand of air compressor frequency conversion control transformation The power frequency and frequency conversion condition of air compressor are often larger than that of air compressor. The starting mode is mostly under no-load condition. Start the star angle start, and the immediate and unloading is done in an instant. This makes the air compressor reach 47 times of the rated current instantaneously at the starting current, and the mechanical impact is greater when the value and the unloading; the large impact on the power supply due to the large current change during starting, and the fluctuation of the air source Affecting production; at the same time, this type of operation thus has a large mechanical impact, which accelerates the wear of the equipment and reduces the service life of the equipment; since the conventional air compressor's drag motor itself does not have a speed control function, it is not possible to directly use pressure flow and other changes. The purpose of the speed reduction adjustment is to match the output power, and the motor cannot be started frequently during use, so that the operation must be controlled when the gas volume needs to be small, and the energy waste is serious.
The frequency conversion speed regulation technology has obvious power saving effect, and its excellent speed regulation capability has wide adaptability and is safe and reliable. Smooth shifting performance and soft start mode can reduce the impact on the machine during start-up and shifting, prolong the service life of the equipment; in addition, the frequency can be changed when the motor is running, which realizes the adjustment of the output power of the air compressor. When the gas volume is small, the speed of the motor can be reduced, and the air pressure is not required to be loaded and unloaded, thereby greatly improving the operating power of the motor, so that the pneumatic gas supply system can maintain the frequency control of the relatively stable air machine. The meaning of the air machine through the frequency conversion speed regulation can highlight the following advantages to save energy, improve the system's gas supply effect, reduce the operating cost, improve the accuracy of pressure control, extend the life of the compressor, reduce its operating noise and increase the power factor, the maximum The reduction of the energy consumption of the high-volume operation of the air compressor within the scope has fundamentally improved the operating cost and working conditions of the air compressor.
2.2 Air compressor frequency conversion speed regulation transformation requirements In the air compressor transformation, the output pressure of the gas storage tank should be stable when the motor frequency conversion operation, the fluctuation range should be within the scope of production demand; the system should have frequency conversion when controlling And power frequency two control loops, the role of power frequency control is to assist the completion of the control when the inverter system fails, so as to ensure that the production is not affected; in the transformation, the motor should be guaranteed according to the specific working conditions of the air compressor. The performance characteristics of the torque to highlight the advantages of frequency conversion; in order to prevent the influence of various external disturbances on the air compressor, the input end of the frequency converter should have a certain ability to resist electromagnetic interference; in the case of reduced gas demand, the frequency converter is Low frequency operation, at this time should ensure that the winding temperature of the motor and the running noise of the motor do not exceed the normal value; if the production process changes, the modified frequency conversion control system should be able to adjust the air supply pressure, using constant air pressure and variable flow mode. Supply air.
3 Air compressor frequency conversion speed regulation energy saving example analysis 3.1 Reconstruction specific situation The purpose of the transformation is to transform the air compressor control mode to achieve the purpose of energy saving operation hall. Frequency conversion energy saving according to the mechanism of frequency conversion speed regulation. There is a close relationship between the speed of the asynchronous motor and the power frequency. The frequency of the power supply will directly affect the speed of the motor. When the winding pole pair of the motor and the motor slip rate are fixed, the motor speed and The frequency of the input power supply is proportional to the frequency of the input power supply. Therefore, changing the frequency of the input power supply can change the speed of the motor, thereby realizing the energy-saving mechanism of the frequency conversion speed regulation 2 frequency conversion speed regulation. When the motor is working, the power of the load is closely related to the speed, and the shaft power of the motor is The motor's speed is also proportional, so the motor's operating power is reduced as the motor speed drops, so you can save energy by shifting. The air compressor is a constant torque load condition. The torque is the same at different speeds, but the power is proportional to the speed. Therefore, when the speed is reduced, the power will also decrease, so energy can be saved.
I.2 Air compressor energy consumption analysis Different air compressors before the transformation have two working conditions in the working state, the loading state is no-load state. When loading, the air intake of the air compressor is opened, and the air is taken in to output compressed air to provide high-pressure air for production; when the air load is empty, the intake valve of the air compressor is closed, and the compressed air is stopped, and the state is idling. In the idling state, the motor needs to overcome the mechanical resistance and needs to consume 30 energy of the rated power, so if the compressor of the station 1601 is unloaded, it still needs to bear the power 48.
The control of the common air compressor in production is the upper and lower limit mode. The power consumption of the air compressor is proportional to the output pressure. The higher the output pressure, the higher the power consumption. From the lower limit of the output pressure to the upper limit, the total power consumed. At 10.
The air-shrinking machine of Taiwan Training is about the power of the consumption of electricity. If there are multiple air compressors in the air pressure system, each of them needs to change the upper and lower limits in the constant pressure adjustment, which will undoubtedly increase the power consumption of the whole system. Is a waste of resources.
3.3 Energy-saving mechanism of variable frequency air compressor The pressure setting of the variable frequency air compressor is a point, that is, the rated pressure parameter of the production equipment will be met as the rated pressure of the system. The variable frequency air compressor will automatically adjust the air compression according to the change trend of the pressure in the whole system. The speed of the machine is used to balance the output of the compressed air, thereby ensuring the stability of the entire network and meeting the production requirements. This reduces the unloading operation of the air compressor and saves energy; at the same time, the frequency conversion technology makes the start of the air compressor smooth, eliminates the current impact, and reduces the energy consumption of frequent shifting.
3.1 Reconstruction of Fangfang 3.4.1 If the equipment type of the air compressor station is the same in the transformation and reconstruction of the air compressor station, only the inverter air compressor must be configured, that is, only the equipment of the air compressor should be modified, and other With the cooperation of power frequency air compressors, the goal of reducing energy consumption can be achieved. When the air consumption generated by the air compressor station is less than the air volume of the air compressor, the air compressor can be used to complete the air supply. If the air consumption is greater than the gas production capacity of the station, the ordinary air compressor needs to be started to complete the compensation. In the loading state, the situation of linkage with the inverter device can be realized. This method is to reduce the energy consumption by maintaining the balance of the gas supply system.
3.4.2 Specific control measures With the above transformation analysis, the air compressor will be transformed into a frequency conversion equipment. At the same time of frequency conversion control, manual control measures should be provided to provide backup control mode for the frequency converter. The specific frequency conversion control method is as follows: the operation of the air compressor is still completed by the computer of the machine, and the original protection and loading operation mode are unchanged. The motor speed adjustment of the air compressor is controlled by the frequency converter. The basis of the control is based on the pressure measurement and control installed in the gas storage tank to transmit the collected air pressure signal to the frequency converter. The frequency converter adjusts the output frequency according to the change trend of the air pressure to control The motor speed of the air compressor reaches the target of adjusting the pressure. The computer parameters of the air compressor itself should be coordinated with the inverter control output parameters, that is, the synchronization and control can be realized to ensure the energy saving effect.
3.4.3 The specific control mode The air compressor operation after the transformation is still dominated by the voltage control of the machine. The startup or shutdown and the viewing of various parameters are all used as the platform. If you want to modify the pressure, you must modify it at the same time on the electromechanical inverter. If you switch the inverter air compressor back to the original power frequency mode, you need to manually switch on the control panel.
3.5 The specific transformation object should first control the harmonic interference that the inverter may bring, reduce its negative impact on the power supply and equipment, install the filter; use the professional frequency converter software to modify the air compressor program, The function of temperature protection and reverse protection of the main motor is added; the protection of the motor overload should be carried out by the inverter; the principle of the motor 4 is guaranteed. The fundamental principle of the frequency conversion speed regulation technology is to affect the running speed of the motor by changing the frequency of the input current of the motor. The torque control is achieved.
If the AC motor of the air compressor is running under the power frequency condition, its starting force will consume a lot of electric energy during the load-load unloading process, and these electric energy cannot be the effective power for the production service. Therefore, the air pressure is controlled by the frequency conversion speed regulation technology. Machine costs to achieve energy saving goals.
Li Jixing. The basic theory and practical knife of frequency conversion speed regulation technology. Inner Mongolia Huang Jun, Chen Qing, Luo Wei. The application of frequency conversion speed regulation technology in the reform of wind turbine belt and energy saving analysis. Guangxi Light Industry, 200710.
Liu Liu. The application of frequency conversion speed regulation technology on the sock machine. China Science and Technology Zhou Jing. The self-control design of the frequency conversion speed control technology. Medical engineering design, Lu Yuanxiang. Talking about AC motor frequency conversion speed regulation technology and night machine Qi Qishou, Guo Xiaoli, Liu Benhui, etc. Based on the 5 Li control AC motor frequency control technology magic. Mechanical Engineer, 200712.
Chen Xuefeng. Talking about the application of frequency conversion technology. Scientific and technological information development and Xu Zhen. The development of turbulent motor frequency control technology is a fantasy. Micro-specialty is connected to the fifth page of a major accident or loss, which must be taken seriously and effective measures taken.
6 Several misunderstandings in the mechanical seal inspection of the pump The greater the compression of the spring, the better the sealing effect. In fact, if the spring compression amount is too large, the friction pair may be sharply worn and burned instantaneously; excessive compression causes the spring to lose the ability to adjust the end face of the moving ring, resulting in seal failure.
The tighter the moving ring seal, the better. In fact, the dynamic ring seal is too tight and harmful. It is to aggravate the wear between the seal ring and the bushing, premature leakage; it increases the resistance of the moving ring axial adjustment movement, and can not be adjusted in time when the working conditions change frequently; it is easy to damage the spring excessive fatigue; The deformation of the ring affects the sealing effect.
The tighter the static ring seal, the better. The static ring seal is basically at rest, and the relatively tight seal will be better, but too tight is also harmful. It is caused by excessive deformation of the static ring seal, which affects the sealing effect. The static ring material is mostly graphite, which is brittle. Excessive force is easy to cause chipping. It is difficult to install and disassemble, and it is easy to damage the static ring.
The tighter the impeller lock is, the better. In the mechanical seal leakage, leakage between the shaft sleeve and the shaft is relatively common. It is generally believed that the leakage between the shafts is that the impeller locks are not locked. In fact, there are many factors causing leakage between the shafts, such as the failure of the inter-axis pads, the offset, the impurities between the shafts, and the coordination between the shaft and the sleeve is too long. Etc. will cause leakage between the shafts. Excessive locking of the lock nut will only lead to premature failure of the inter-axis pad. On the contrary, the lock nut is moderately locked, so that the inter-axle pad always maintains a constant compression elasticity. During operation, the lock nut will automatically lock in time, so that the shaft is always in good condition. The new one is better than the old one. Relatively speaking, the effect of using a new mechanical seal is better than that of the old one, but the quality or material selection of the new mechanical seal is not appropriate. The large dimensional error will affect the sealing effect; in the polymerizable and permeable medium, the static ring is not excessive. Wear or not replace it as well. Because the static ring is in a static state for a long time in the static ring seat, the polymer and impurities are deposited as a body, which plays a good sealing role.
The repair is better than not. Once the mechanical seal leaks, it is rushed to repair. In fact, sometimes the seal is not damaged. It is only necessary to adjust the working condition or adjust the seal properly to eliminate the leak. In this way, it avoids waste and can verify its own fault judgment ability, and accumulates maintenance experience to improve the quality of maintenance.
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