Les fournisseurs de dispositifs de récupération d'énergie pour convertisseurs de fréquence rappellent que, dans l'industrie moderne, les moteurs constituent un type d'équipement énergivore aux applications très diverses. Selon les statistiques, la capacité installée totale de la Chine s'élève à environ 400 millions de kilowatts, pour une consommation annuelle d'électricité d'environ 600 milliards de kilowattheures, soit 70 à 80 % de la consommation industrielle. La Chine utilise principalement des moteurs de petite et moyenne puissance (environ 80 %), qui représentent 90 % des pertes totales d'électricité. En pratique, l'utilisation des moteurs en Chine accuse un retard important par rapport à l'étranger : le rendement unitaire est de 75 %, soit 10 % de moins qu'à l'international ; le rendement global du système, de 30 à 40 %, est inférieur de 20 à 30 % aux normes internationales. Par conséquent, les moteurs de petite et moyenne puissance en Chine présentent un fort potentiel d'économie d'énergie, et la promotion de leur efficacité énergétique est impérative.
Grâce à leur structure simple, leur facilité de fabrication, leur faible coût, leur durabilité, leur fonctionnement fiable et leur capacité à résister aux environnements difficiles, les moteurs asynchrones sont largement utilisés dans la production industrielle et agricole. Leur efficacité énergétique, notamment pour l'entraînement de pompes et de ventilateurs dans diverses industries, est particulièrement appréciée.
With the rapid development of science and technology, especially the high development and application of power electronics technology, microelectronics technology, and automatic control technology, the energy-saving effect of frequency converters has become more significant. It can not only achieve stepless speed regulation, but also operate efficiently under different loads, with good dynamic characteristics, and can achieve high-performance, high reliability, and high-precision automatic control. Compared to other speed regulation methods such as voltage reduction speed regulation, pole changing speed regulation, slip speed regulation, AC cascade speed regulation, etc., variable frequency speed regulation has stable performance, wide speed regulation range, and high efficiency. With the development of modern control theory and power electronics technology, AC variable frequency speed regulation technology is becoming increasingly perfect and has become the trend of AC motor speed regulation. Variable frequency speed control devices (VFDs) have been widely used in the industrial field.
The use of frequency converters for speed control signal transmission is fast, the control system has a small time delay, the response is sensitive, the control accuracy of the adjustment system is high, the use is convenient, and it is conducive to improving production output, ensuring quality, and reducing production costs. Therefore, the use of frequency converters is a popular product for energy-saving and consumption reduction in factories and mining enterprises.
Variable frequency motor energy-saving device is a revolutionary new generation of motor specific control product. Based on microprocessor digital control technology, it dynamically adjusts the voltage and current in the motor operation engineering through its built-in dedicated energy-saving optimization control software. Without changing the motor speed, it ensures that the output torque of the motor matches the load demand accurately, effectively avoiding the waste of electrical energy caused by excessive output of the motor.
AC motors are currently the most widely used motors, accounting for about 85% of all types of motors. They have the advantages of simple structure, low cost, and no maintenance required. However, their weakness is the difficulty of speed regulation, which limits their use in many applications or requires mechanical means to achieve speed regulation.
There are two typical applications of frequency converters in terms of load types: 1. Constant torque application; 2. Variable torque application. In terms of application purposes, the main objectives are: 1. To improve the process, ensuring the rotational speed during the process, the rotational speed under different loads, and accurate positioning. With its excellent speed regulation performance, it can improve productivity, enhance product quality, improve comfort, rationalize equipment, adapt or improve the environment, etc. 2. The main purpose of energy-saving transformation is to achieve significant results by controlling the speed of fans and pumps that require flow or pressure regulation.
The principle of variable frequency speed regulation
Motor loads such as fans, water pumps, air compressors, hydraulic oil pumps, and circulation pumps account for the vast majority of the power consuming equipment used in enterprises. Due to technical limitations, almost all flow, pressure, or air volume control systems for such loads are valve controlled systems, where the motor is driven at rated speed and the system provides constant flow, pressure, or air volume. When the equipment's operating requirements change, the load flow, pressure, or air volume is adjusted by overflow, relief valves, or proportional regulators located at the outlet end to meet the changing needs of the equipment's operating conditions. After the overflow valve or proportional control valve overflows, a large amount of energy will be released, and this dissipated energy is actually a part of the energy absorbed by the motor from the power grid, causing great waste of electrical energy. From the working characteristics of this type of load, it can be seen that the motor power is proportional to the cube of the speed, and the speed is proportional to the frequency. If we change the working mode of the motor so that it does not always operate at the rated working frequency, but instead uses a variable frequency adjustment control system for start stop control and adjustment operation, its speed can be continuously adjustable within the range of 0~2900r/min, that is, the output flow rate, pressure or air volume can also be continuously adjustable within the range of 0~100%, so as to accurately match the working needs of the load and achieve the goal of energy conservation and consumption reduction.
The AC motor speed is as follows: n=60f (1-s)/p
In the formula: n=motor speed
F=power frequency
P=number of poles of the motor
S=slip rate
As can be seen from the equation, the synchronous speed n of an AC motor is directly proportional to the power frequency f. Therefore, changing the power frequency can change the motor speed and achieve the purpose of speed regulation.
Principle of variable frequency speed regulation for energy saving
La régulation de vitesse à fréquence variable permet de réaliser des économies d'électricité ; comme son nom l'indique, seule cette régulation permet de réduire la consommation électrique. Vous trouverez ci-dessous une analyse des principes d'économie d'énergie pour deux applications de charge typiques.
(1) Applications de charge à couple constant
Une charge à couple constant signifie que, quelles que soient les variations de vitesse, le couple de charge reste constant.
La formule suivante : P=K * T * N
K = coefficient
P = puissance à l'arbre
T = couple de charge
N = vitesse de rotation
La formule ci-dessus montre que la puissance à l'arbre est directement proportionnelle à la vitesse du moteur. En ajustant la vitesse du moteur en fonction des besoins du processus, on obtient naturellement une économie d'énergie proportionnelle.
(2) Applications à charge à couple variable
Les ventilateurs et les pompes centrifuges sont des charges à couple variable typiques, et leur fonctionnement se caractérise par une utilisation continue et prolongée. Le couple de charge étant proportionnel au carré de la vitesse, tout dépassement de la vitesse nominale entraîne une surcharge importante du moteur. C'est pourquoi, en général, les ventilateurs et les pompes ne fonctionnent pas au-delà de leur fréquence nominale.