05 Sep 2020
Fountains are one of the important entertainment facilities in modern city life. Music fountain are not uncommon. It has long been explained in physics. According to Pascal's theorem, as long as there is a water tower high enough to form a pressure head, an artificial fountain can be made. The most famous fountain in the ancient gardens of our country is probably regarded as the big water method of the Western House in Yuanmingyuan. It was built in the tenth year of Qianlong in the Qing Dynasty (1745), and the designer was Frenchman Jiang Youren. Two years later, the first project, Humorous Fun, was completed. In the twenty-fourth year of Qianlong (1759), the entire Western Building attraction hosted by him and the Italian Castiglione was completed. You can still see a tall rectangular table nearby, which is said to be the foundation of the reservoir (water tower). Not only was it difficult to build at the beginning, but it was just about pumping a large amount of water into a tall water tower. In the era without electric water pumps, how many people would have to work for the emperor to watch it! Before the completion of Dashuifa, there was already a scenic spot called "Shuimu Mingse" in the Old Summer Palace. Although it is not a fountain, it is also ingenious. It uses water to drive a fan to escape the heat. Nowadays, people only know that there are electric fans, don't they know that there were "water fans" in China more than 200 years ago. It embodies the wisdom of the Chinese working people, and also explains the ancient Chinese people's understanding of some natural phenomena and the achievements in exploring some natural laws.
Talk less gossip, the book is back to the main story. It's fine now, the tap water itself is under pressure, and it is extremely easy to add a high-pressure pump if it is not enough. The technology of design and construction is long gone, and there is no need to hire foreign experts. Moreover, the fountain heads form a group of fountains to be bold and spectacular. Some people say that this is not enough. It must be illuminated with colored lights to make the scenery colorful and dubbing accompaniment more active. As a result, the icing on the cake became more and more fascinating. Later, the 18 martial arts such as remote control, program control, and computer control in modern automation technology were used all in one brain. In this way, the sprayed water is more dynamic, which is far different from the monotonous water column. The waterway system of the fountain is nothing more than a pump and a valve, but in order to get colorful changes, the two cannot be static, at least one of them is changing. Therefore, a variable-speed pump is used to obtain the variable water pressure. Or use a valve that can adjust the resistance to obtain a changing water flow by changing the flow resistance. The pumps and valves used here should be anti-clogging, wear-resistant, fast-moving and easy to operate. Of course, it must be rust and corrosion resistant. Because the water in the fountain inevitably has debris, and the flow pattern of the fountain has rhythmic requirements, it must be fast, and it must be prohibited and not dragged. In order to meet the above requirements, special equipment is often used.
The above-mentioned variable speed pump should be driven by a variable speed motor, while ordinary AC motors cannot change the speed in a wide range, and must be matched with a "frequency conversion speed control circuit" to be most suitable for fountain control requirements. The circuit that controls the fountain often cannot rely solely on switching signals, such as the height, direction, change speed, pause time, etc. of the fountain water column, which are all continuous variables, especially when it is matched with music, it is not capable of switching actions, so it is perfect The fountain control circuit should be a program control circuit. Of course, small-scale fountains can also be controlled by cam sequence similar to automatic washing machines. Large-area fountain groups or fountains that work for a long time, especially fountains with variable frequency speed pumps, should be composed of microprocessors. The contact controller is designed according to the program control. This kind of non-contact controller composed of a microprocessor does not need to be specially made, and can use the "programmable logic controller" (abbreviated as "programmable controller" or represented by PLC) widely used in industry as the main body, and external configuration Several auxiliary circuits such as interfaces can be connected to the frequency converter and valve to work. "Programmable" means that the program can be written arbitrarily, and of course it can be changed arbitrarily, which is very flexible for users. The water flow of the fountain can be up and down according to the rhythm of the music, and the audience will gradually become intoxicated under the beautiful scenery and the sound of music.
What is the programmable logic controller mentioned above? He doesn't have deep principles, but he has some modern control ideas. It is a bit like the controller in a fully automatic washing machine controlled by a microprocessor, but with more functions and a larger scale. It includes clock, input and output interface, logic operation circuit that can be combined arbitrarily, program memory, etc. It can be connected to many input switch signals and many output switch actuators, and it also has a small amount of analog (continuously increasing or decreasing variables) input and output interfaces, which is very convenient to use. And there are no cams, contacts, relays and other parts with mechanical movement and electrical contacts, so it is small in size, long in life, and high in reliability. Programmable logic controllers are very common in the field of automation, especially in logic control systems and program control systems based on various switch signals, and they are more handy. But it is not so popular in daily life at present, and it is just a rough mention here.
The purpose and advantages of using the inverter?
Frequency conversion speed regulation has been recognized as one of the most ideal and most promising speed regulation methods. The main purpose of using general-purpose inverters to form a frequency conversion speed regulation transmission system is to increase labor productivity, improve product quality, and improve equipment. Requirements for automation, improving the quality of life and improving the living environment; the second is to save energy and reduce production costs. Users can choose different types of inverters according to their actual process requirements and application occasions.
The correct selection of general-purpose inverters is very important to the normal operation of the drive control system. First, the purpose of using general-purpose inverters must be clarified, according to the type of production machinery, speed range, speed response and control accuracy, starting torque and other requirements , Fully understand the characteristics of the load driven by the inverter, decide which function of the general inverter to use to form the control system, and then decide which control method is most suitable. The general-purpose inverter selected should not only meet the requirements of the production process, but also be reasonable in terms of technical and economic indicators. Improper selection, system design, and use of general-purpose inverters will often cause the same-used inverters to fail to operate normally, fail to achieve the expected goals, and even cause equipment failures and cause unnecessary losses. In addition, in order to ensure the long-term reliable operation of general-purpose inverters, the connection of the inverter ground wire is also very important.
How does variable frequency speed regulation save energy?
Since the frequency conversion speed regulation is adopted, the energy saving effect of fans and pumps is the most obvious, and the power saving rate can reach 20%-60%. This is because the power consumption of the fan and pump is proportional to the third power of the speed. When the user needs When the average flow rate is small, the speed of the fan and water pump is low, and the energy saving effect is also very considerable. However, when the traditional baffle and method adjust the flow, the power consumption does not change much. Since there are many such loads, accounting for about 20%-30% of the total capacity of AC motors, their energy saving is of great significance.
For some constant torque loads running at low speeds, such as conveyor belts, variable frequency speed regulation can also save energy. In addition, the original speed control methods that consume more energy (such as wound rotor motors, etc.), the original speed control methods are more complex and less efficient (such as gantry planers, etc.), after adopting frequency conversion speed control, The energy saving effect is also obvious.
What are the advantages of variable frequency speed regulation in motor operation?
Frequency conversion speed regulation can easily realize the forward and reverse rotation of the motor. Only need to change the switching sequence of the inverter tube inside the frequency converter to realize the output commutation, and there is no problem of burning the motor due to improper commutation.
Most of the frequency conversion speed control system starts from a low speed and the frequency is low. The acceleration and deceleration time can be set arbitrarily, so the acceleration and deceleration time is relatively smooth, the starting current is small, and higher frequency start and stop can be performed.
When the frequency conversion speed regulation system is braking, the inverter can use its own braking circuit to consume the energy of the mechanical load on the braking resistor, and it can also feed back to the power supply grid, but the feedback to the grid requires special accessories, which requires a large investment. In addition, the frequency converter also has a DC braking function. When braking is required, the frequency converter applies a DC voltage to the motor for braking, and no additional braking control circuit is required.
Originally published 05 Sep 2020, updated 05 Sep 2020.