CNThe line reactor can not only prevent the interference from the power grid, but also reduce the pollution to the power grid caused by the harmonic current generated by the rectifier unit. The rectifier diodes and filter capacitors in the device are harmful. Therefore, it is beneficial to improve the operating condition of the frequency converter by connecting the line reactor. According to the operation experience, the line reactor must be installed in the following occasions to ensure the reliable operation of the inverter.
The power supply capacity is 600kVA and above, and the installation position of the inverter is within 10m from the large-capacity power supply; the unbalance rate of the three-phase power supply voltage is greater than 3%; other thyristor converters share the same incoming power supply with the inverter, or the incoming power supply terminal A capacitor device that is switched by a switch to adjust the power factor is connected.
Selection of line reactor capacity The capacity of the line reactor can be determined according to the expected voltage drop on each phase winding of the reactor. Generally, the voltage drop is selected as 2%~4% of the phase voltage of the grid side. The voltage drop of the line reactor should not be too large, and the voltage drop will affect the motor torque if the voltage drop is too large. In general, it is enough to select 4% (8.8V) of the incoming line voltage, and a 10V voltage drop can be selected for larger-capacity inverters such as 75kW and above.
The role of DC reactor and output reactor In the frequency conversion system with DC link, connecting the DC reactor behind the rectifier can effectively improve the power factor, and the power factor can be increased to 0.95 with proper coordination. In addition, the DC reactor can make The inverter runs stably and can limit the short-circuit current, so many inverters of more than 55kW produced by many manufacturers are supplied with DC reactors. The main function of the output reactor is to compensate the influence of long-line distributed capacitance, and to suppress the harmonics output by the frequency converter, thereby reducing the noise of the frequency converter.
