Many people do not understand how to choose a variable frequency power supply. This article intends to introduce the factors to be considered when selecting a variable frequency power supply: first, according to the type of mechanical equipment, load torque characteristics, speed range, starting torque and use environment. Requirements, and then decide which control method and protective structure of the variable frequency power supply is suitable.
First, select the variable frequency power supply with appropriate control according to the load characteristics. Nowadays, there are many kinds of variable frequency power supplies available on the market, and the functions are also increasingly powerful. The performance of variable frequency power supplies has become the decisive factor of the speed control performance. In addition to the "innate" conditions of the manufacturing process of the variable frequency power supply, the frequency conversion power supply is adopted. What kind of control is also very important.
Second, the load torque characteristics of mechanical equipment. In practice, production machines are often divided into three types according to the characteristics of load torque: constant torque load, constant power load and fluid load.
1. Constant torque load. When the variable frequency power supply is dragged by a constant torque load, the output torque at a low speed is large enough and sufficient overload capability is required. If you need to run at a low speed for a long time, you should consider the heat dissipation capability of the standard cage asynchronous motor to avoid excessive temperature rise of the motor.
2. Constant power load. The constant power nature of the load should be in terms of a range of speed variations. When the speed is very low, due to the limitation of mechanical strength, TL cannot be infinitely increased, and it is converted to a constant torque property at a low speed. The constant power zone and constant torque zone of the load have a great influence on the choice of the transmission scheme. When the motor is in constant flux regulation, the Zui large allowable output torque is constant, which belongs to constant torque speed regulation. In the case of weak magnetic speed regulation, the large allowable output torque of Zui is inversely proportional to the speed, which belongs to constant power speed regulation.
3. Fluid load. The torque of this type of load is proportional to the square of the speed, and the power is proportional to the cube of the speed. Various fans, pumps and oil pumps are typical fluid loads.
Third, according to the installation environment, select the protection structure of the variable frequency power supply. The protective structure of the variable frequency power supply should be compatible with the installation environment. This should consider environmental temperature, humidity, dust, pH, corrosive gas and other factors, which is related to the long-term, safe and reliable operation of the variable frequency power supply.
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