How to choose VFD (Variable-frequency Drive)

Performance - Choose a VFD (Variable-frequency Drive) with appropriate performance according to process requirements. Do not pursue high performance one-sidedly, because the higher the performance, the higher the price. VFD (Variable-frequency Drive) for fans and water pumps, ordinary sinusoidal pulse width modulated VFD (Variable-frequency Drive) can meet the requirements, because fans and water pumps are square torque loads, and the torque drops significantly at low speeds, and the fan and water pumps High-precision speed and complex control functions (such as forward and reverse rotation, etc.) are not required.

If you are controlling a compressor, since the torque characteristics of the compressor are relatively complex, especially the starting torque is very large, you should choose a vector VFD (Variable-frequency Drive) with good torque characteristics and a current limiting function. If it is used for papermaking and chemical fiber equipment, a closed-loop vector VFD (Variable-frequency Drive) with high precision and high response characteristics should be selected. Reliability - The purpose of using VFD (Variable-frequency Drive) is to improve production efficiency. If the performance is good but the reliability is not good and problems often occur, then the gain outweighs the loss. China has a vast territory. The southern region has high temperature and humidity all year round, and the coastal areas are dominated by salt corrosion. These will cause the insulation of equipment to decrease. The northern climate is dry and prone to static electricity. The temperature difference between winter and summer is large. The production environment of each enterprise is even more different. These factors should be considered when purchasing a VFD (Variable-frequency Drive). Although some VFDs (Variable-frequency Drives) perform very well, they have poor environmental adaptability and may often break down and affect production.

In addition, the power modules of the key components of VFD (Variable-frequency Drive) now generally use IGBT modules and IPM intelligent power modules, especially IPM modules. Although the cost is higher, due to the internal problems of overcurrent, short circuit, and undervoltage, the module , output grounding, overheating and other protection functions. Once an abnormality occurs, the module will immediately protect itself internally, and then perform secondary protection through an external protection circuit. The possibility of burning the module is greatly reduced, and the reliability is significantly improved. For products using GTR modules, since the GTR itself has no protection function, and the external protection circuit and push circuit are very complex, once the protection cannot keep up, the module will burn out in an instant.

In order to reduce costs, some manufacturers still use GTR modules. This is something you need to pay attention to when purchasing a VFD (Variable-frequency Drive). Price - This is the main factor to consider when purchasing a VFD (Variable-frequency Drive). However, if you pursue low price one-sidedly, it will often lead to a decrease in quality and reliability, because the power devices and main components in the VFD (Variable-frequency Drive) Loop electrolytic capacitors account for about 70% of the cost. In order to reduce costs, some manufacturers use 1000-volt modules instead of 1200-volt modules, use 25A current modules instead of 30A modules, and use ordinary low-frequency electrolytic capacitors instead of VFD (Variable-frequency Drive) Dedicated high-frequency electrolytic capacitors, this VFD (Variable-frequency Drive) will not cause any problems under normal circumstances or for a short period of time. However, due to the reduced power margin of the module, once the motor stalls or the power grid instantaneously High voltage, sustained high temperature, etc. can easily cause damage.

After-sales service - No matter how good the product is, there is a possibility of failure. If you choose a manufacturer or dealer with good technical strength and after-sales service, you can get thoughtful technical services and avoid worries.