Select the main points of frequency conversion power supply and the scope of application of frequency conversion power supply
The correct selection of frequency conversion power supply is essential for the normal operation of the mechanical control system of mechanical equipment. When selecting a variable frequency power supply, first of all, according to the requirements of the type of mechanical equipment, load torque characteristics, speed range, static speed accuracy, starting torque and use environment, then decide which control method and protective structure of the variable frequency power supply is most suitable. The so-called combined use is to achieve the best cost performance of variable frequency power supply applications on the premise of meeting the actual process production requirements and use occasions of mechanical equipment.
The first point. According to the load characteristics, select the appropriate frequency control power supply
There are many types of variable frequency power supplies on the market, and their functions are becoming more and more powerful. The performance of variable frequency power supplies has become a deciding factor for the performance of variable speed power supplies. What kind of control method is also very important. The following table summarizes the performance characteristics of various variable frequency power supply control methods in recent years.
In summary, the use of different control methods for the variable frequency control of asynchronous motors can provide speed regulation characteristics with different performance characteristics.
The second point. According to the installation environment, select the protective structure of the variable frequency power supply
The protection structure of the variable frequency power supply should be compatible with its installation environment, which must take into account factors such as ambient temperature, humidity, dust, acidity, alkalinity, and corrosive gases. This is related to the long-term, safe and reliable operation of the variable frequency power supply. Most inverter power supply manufacturers can provide the following commonly used protective structures for users to choose:
(1) Open type IP00, which protects the human body from touching the live part inside the inverter power supply from the front. It is suitable for installation on the screen, panel and shelf in the electric control cabinet or electrical room, especially for the centralized use of multiple inverter power supplies. Good, but it has higher requirements for the installation environment.
(2) Enclosed IP20, IP21, this protective structure of variable frequency power supply has a cover around, can be wall-mounted installation on the wall in the building, it is suitable for most indoor installation environments.
(3) Sealed IP40, IP42, it is suitable for occasions with poor industrial site environmental conditions.
(4) Sealed type IP54, IP55, it has a dust-proof, waterproof protective structure, suitable for occasions with poor environmental conditions on the industrial site, water spray, dust and certain corrosive gases.
Point 3. Load torque characteristics of mechanical equipment
In practice, people often divide production machinery into three types according to the load torque characteristics: constant torque load, constant power load and fluid load.
1 Constant torque load In this type of load, the load torque TL has nothing to do with the speed n, TL always remains constant or substantially constant at any speed, and the load power increases linearly with the increase in load speed. Friction loads such as conveyor belts, mixers, extruders, and feed mechanisms of mechanical equipment, and gravity loads such as cranes, hoists, and elevators are all constant torque loads.
When the variable frequency power supply drags the load of constant torque nature, the output torque at low speed should be large enough and must have sufficient overload capacity. If you need to run at a low speed for a long time and stable speed, you should consider the heat dissipation capacity of the standard cage asynchronous motor to avoid excessive temperature rise of the motor.
2 Constant power load The characteristic of this type of load is that the required torque TL is roughly inversely proportional to the speed n, but its product, that is, the power, remains approximately unchanged. The main shafts of metal cutting machine tools, rolling mills, paper machines, coilers and uncoiling machines in film production lines are all constant power loads.
The constant power nature of the load should be in terms of a certain range of speed changes. When the speed is very low, TL cannot be infinitely increased due to the limitation of mechanical strength, and it changes to a constant torque property at low speed. The constant power area and constant torque area of ​​the load have a great influence on the choice of transmission scheme. When the motor is under constant flux control, the maximum allowable output torque is unchanged, which belongs to constant torque speed control; while when the field weakening speed is adjusted, the maximum allowable output torque is inversely proportional to the speed and belongs to constant power speed control. If the range of the motor's constant torque and constant power speed regulation is consistent with the load's constant torque and constant power range, the so-called "matching" situation, the capacity of the motor and the frequency conversion power supply are the smallest.
3 Fluid type load The torque of this type of load is proportional to the second power of speed, and the power is proportional to the third power of speed. Various fans, water pumps and oil pumps are typical fluid loads.
The fluid load can adjust the air volume and flow rate by the variable frequency power supply speed regulation, which can greatly save electrical energy. Because the power demand of fluid load at high speed increases too fast, which is proportional to the cube of the load speed, it should not be allowed to run this type of load over power frequency.
This European Style Table Clock with the main material of Metal, ABS and PVC, is suitable for desk decoration. European Style Table Clock has 12/24 hour format. It is a battery operated clock, when you install battery(not including), the flip card will automatically down minute by minute, European Style Table Clock will let you in a deep thinking.
This clock with CE & ROHS certificate.
Different size can be chosen: 36*16.7*8.5CM, 21*8.5*11CM
Different colors are available: stainless steel, golden customized colors
Material available: metal, bamboo, wooden, plastic
European Style Table Clock,Decorative Table Clocks,Antique Clocks,Large Vintage Table Clock
Guangzhou Huan Yu Clocking Technologies Co., Ltd. , https://www.mk-time.com