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A line reactor (also referred to as a "choke") is a variable frequency drive (VFD) accessory that consists of a coil of wire that forms a magnetic field as current flows through it. This magnetic field limits the rate of rise of the current, thus reducing harmonics and protecting the drive from power system surges and transients. There are two primary types of reactors used in variable frequency drives: AC & DC. When an AC reactor is placed between the power system and the drive, it is referred to as an AC line reactor. When a DC reactor is inserted into the DC link of a variable frequency drive, it is known as a DC link reactor. Both AC and DC reactors limit harmonic currents. However, AC reactors have the significant advantage of protecting the entire VFD from power system surges and transients since they are placed between the power system and the incoming power terminals at the drive. Reactors can prevent overvoltage trips, increase the reliability and life span of the VFD, improve total power factor, and reduce nuisance tripping.
This operation is used when sudden deceleration or stops are frequently performed, or when the deceleration time must be shortened on loads having a large inertia.This resistor is for taking up energy during power generation braking.
DC reactor is used to improve the input power factor of the inverter power supply and reduce harmonics.Install DC-reactor when the power supply capacity is 500 kVA or more and the power supply capacity is 10 times or more than that of the inverter's capacity, or when a distortion generating source such as a thyristor or a large-capacity inverter is connected to the same wiring leads.
On systems that run 400 V class general-purpose motors by voltage-type PWM system inverters using ultra high-speed switching devices (e.g. IGBT), surge voltage, that is dependent on cable length, cable laying methods, cable constants, and other factors, sometimes causes the insulation of the motor winding to deteriorate. For this reason, measures for suppressing surge voltage are performed by installing a DC reactor or surge suppression filter on the inverter output end where the insulation-reinforced motor is used.
The embedding of microprocessor chip technology and power electronic devices in the design of intelligent AC voltage stabilizers (or automatic voltage regulators (AVR)) led to produce high-quality, stable electric power supply in the event of significant and continuous deviation of mains voltage.