Aug 28, 2020
Discussion on Energy-saving Technology of Motor Frequency Conversion Control and Its Application
Since the reform and opening up, China's social and economic development has been very rapid, including the development of the power economy. However, there are still many shortcomings in the power economy. China's power has always been in short supply, and there will be power shortages in many parts of China. In order to cope with the power shortage, the country organized experts to conduct a lot of research on the energy-saving aspects of electric power. The most prominent one is the energy-saving technology of motor frequency conversion control. Small household appliances at home can use the motor frequency conversion energy-saving technology. That is to say, the development and application of motor energy-saving frequency conversion technology can save the application of electricity to a large extent, and well alleviate the current situation of power shortage in China.
After the sustainable development strategy was put forward in China, many companies and organizations are working hard to realize a low-carbon, energy-saving and environmentally friendly life in the future. Energy saving and emission reduction is an important measure to achieve sustainable development strategy. In terms of power system, energy saving and emission reduction are mainly implemented for fans, motors, and pumps. In order to achieve this goal, vigorously develop and research AC motor variable frequency speed regulation and power saving technology. In China's industry and agriculture, asynchronous AC motors are the most widely used. Asynchronous motors have significant shortcomings such as low power factor, poor speed regulation, and high energy consumption. After applying the motor variable frequency energy-saving technology to asynchronous AC motors, these problems of asynchronous AC motors can be solved well. It can well realize the energy saving and emission reduction work of asynchronous AC motors, and contribute to China's sustainable development strategy.
1. Analysis of the principle and characteristics of motor frequency conversion control technology
Variable-frequency motor is a general term for inverter-driven motors, including two parts: variable-frequency induction motor and inverter, which can improve the working efficiency of the motor and reduce the power consumption. Taking the alternator as an example, its speed formula is as follows:
N1=60 f/p. (1) In formula (1): n1――synchronous speed; f――power frequency, 50 Hz; p――number of magnetic pole pairs of the motor.
The motor slip rate is expressed by the formula: s=(n1?Cn)/n1. (2) In the formula (2): s――motor slip rate;
From equations (1) and (2), it can be inferred: n = 60 f(1-s)/p. (3)
The motor frequency conversion control technology can well control the output frequency and output voltage through the inverter. This is a significant feature of the motor frequency conversion control technology, which is not available in other motor control systems. At the same time, the motor frequency conversion control technology also has the function of soft start and notification. The electromagnetic design is adopted to reduce the resistance of the electronic and rotor. Able to achieve continuously variable speed. Low power consumption, fully reflects the characteristics of energy saving and emission reduction.
2. Development and application analysis of motor frequency conversion control
In the beginning, the frequency of motors in China was fixed, and the motors could only output one power and one voltage. Therefore, the drive frequency of the motor at that time was completely unchanged when it was working. However, the drive frequency required by the load is often constantly changing. In order to meet the drive frequency required by the load, the rated drive frequency of the motor is generally greater than the drive frequency required by the load. Although this can ensure that the motor provides sufficient drive frequency and ensure the normal operation of the motor, a large part of the drive frequency will be wasted, which causes a large amount of electric energy to be wasted and cannot be effectively used. Does not meet the strategic requirements of China's sustainable development. In order to meet the requirements of saving power and making full use of power, motor frequency conversion control technology has been developed. Motor frequency conversion control can change the output power and voltage of the motor according to the driving frequency required by the load, ensuring that there will be no redundant driving Waste, which greatly improves the utilization rate of electric energy, fully meets China's energy saving and emission reduction requirements. As China's requirements for energy conservation and emission reduction become higher and higher, the development and research of frequency conversion energy-saving control systems have also been continuously improved, and they have been better promoted and are applied in more and more places.
2.1 The development process of motor frequency conversion technology
Most of the current motor frequency conversion systems are constant V/F control systems. This frequency conversion control system is characterized by simple structure and cheap production. This system is widely used in large-scale wind turbines and other places where the dynamic performance requirements of the frequency conversion system are not very high. This system is a typical open-loop control system. This system can meet the smooth speed change requirements of most motors, but it has limited dynamic and static adjustment performance, and cannot be applied to those with strict requirements for dynamic and static performance. local. In order to achieve the high performance of dynamic and static adjustment, we can only use a closed-loop control system to achieve. Therefore, some scientific researchers have proposed a motor speed control method that controls the closed-loop slip frequency. This speed control method can achieve high performance in static and dynamic speed control, but this system can only be obtained in a motor with a relatively slow speed. The application should be that when the speed of the motor is high, this system will not only not achieve the purpose of saving energy, but will also cause the motor to generate a great transient current, which makes the torque of the motor change in an instant. Therefore, in order to achieve higher dynamic and static performance at higher speeds, only the problem of transient current generated by the motor must be solved first. Only by solving this problem reasonably can we better develop the motor frequency conversion energy-saving control technology.
2.2 Application of motor frequency conversion control
About 70% of the energy consumption of the motor is applied to the load of fans and pumps, so the motor frequency conversion control technology can save the energy consumption of this part of the load, and achieve the purpose of energy saving and emission reduction. . Take the air conditioner as an example. The air conditioner without frequency conversion control system can only be achieved by closing the air duct when the set temperature is lower than the threshold. However, the motor of the air conditioner is still running at this time. A part of the driving power is not used at all, but simply wasted. However, in the air conditioner that has won the inverter control system, if the temperature of the air conditioner is lowered, only the rotation speed of the motor needs to be controlled to reduce the output driving power. It will waste the driving frequency of the motor, which greatly improves the utilization efficiency of electric energy.
In order to comply with the requirements of China's national sustainable development strategy, the power system vigorously promotes the motor frequency conversion energy-saving control system. The application of this system has greatly eased the current situation of China's power shortage. The motor frequency conversion energy-saving control system can reduce the unnecessary drive frequency output of the motor and achieve the reasonable application of electric power.