【Daily Question 20090215】Why is a reactor needed when using an inverter?
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【Daily Question 20090215】Why is a reactor needed when using an inverter? What is the function of each component on the input side? When should a DC reactor be installed? Summary: DC reactor: It improves the power factor of the inverter and can suppress the harmonics generated by the inverter’s inverting section, thereby reducing their impact on the rectifier unit and the power grid. Input reactor: It prevents the harmonics generated by the inverter from contaminating the power grid; excessive harmonics in the grid can affect the operation of equipment. Output reactor: It makes the AC current generated by frequency conversion pulse width modulation more sinusoidal, thereby reducing the impact on the motor windings as well as the high-frequency electromagnetic waves emitted outward. Reduce the electromagnetic interference emitted by this device to external devices. This post was last edited by lihy on 2009-2-15 21:38]
DC reactor: Installed in the rectifier circuit of the inverter, its function is to improve the power factor of the inverter and to suppress the harmonics generated by the inverter’s inverting section, thereby reducing their impact on the rectifier unit and the power grid. Improve the quality of DC power supply by modulating the rectifier output waveform more ideally. Input reactor: It prevents the harmonics generated by the inverter from contaminating the power grid; excessive harmonics in the grid can affect the operation of equipment. Output reactor: It makes the AC current generated by frequency conversion pulse width modulation more sinusoidal, thereby reducing the impact on the motor windings as well as the high-frequency electromagnetic waves emitted outward. Reduce the electromagnetic interference emitted by this device to external devices.
The input reactor is primarily used to reduce harmonics, surges, and peak currents in the main power supply, to improve resistance to low-frequency conducted interference, to protect the power electronic components of the drive mechanism, to enhance the power factor, and to prevent tripping caused by voltage spikes in the main power supply. The output reactor is primarily used for filtering; generally, the carrier frequency in frequency conversion systems ranges from 2 to 10 kHz. Using it for filtering helps to make the output waveform smoother. A DC reactor is primarily used to generate alternating-current ripple superimposed on the direct-current current, thereby improving the power factor of the inverter. It also helps to suppress the harmonics generated by the inverter’s inversion stage, reducing their impact on the rectifier unit and the power grid.
In frequency conversion systems with a DC link, connecting a DC reactor after the rectifier can effectively improve the power factor; with proper configuration, this value can be increased to 0.95. Additionally, the DC reactor helps to ensure stable operation of the inverter and limits short-circuit currents. Therefore, many manufacturers supply DC reactors as standard equipment for frequency converters of 55 kW and above. The main function of the output reactor is to compensate for the effect of the distributed capacitance in long cables, and it can also suppress the harmonics generated by the inverter, thereby reducing the noise produced by the inverter.
DC reactor: Installed in the rectifier circuit of the inverter, its function is to improve the power factor of the inverter and to suppress the harmonics generated by the inverter’s inverting section, thereby reducing their impact on the rectifier unit and the power grid. Improve the quality of DC power supply by modulating the rectifier output waveform more ideally. Output reactor: It makes the AC current generated by frequency conversion pulse width modulation more sinusoidal, thereby reducing the impact on the motor windings as well as the high-frequency electromagnetic waves emitted outward. Reduce the electromagnetic interference emitted by this device to external devices. Input reactor: It prevents the harmonics generated by the inverter from contaminating the power grid; excessive harmonics in the grid can affect the operation of equipment.
Adding a reactor is mainly to limit harmonic currents. The AC input reactor is used at the front end of the power supply to the inverter, in order to eliminate the impact of grid fluctuations on the inverter and prevent the high harmonics generated by the inverter from contaminating the power supply ； The AC output reactor is used in situations where the distance between the inverter and the motor is relatively large, to eliminate attenuation of the inverter output due to high-order harmonics and similar issues. Generally, for frequency converters above 75KW, a DC reactor is provided as a standard feature. But at present, the quality of our power supplies is relatively poor; it would be much better if the rectifier bridges didn’t break down so often, and if DC reactors were used.
Excessively long cables can severely affect the insulation of both the motor and the cable; it is best to keep the distance between the motor and the frequency converter within 100 meters. If that really doesn’t work, a reactor can be installed on the variable-frequency output line. Reactors play a significant role: they can improve insulation properties and reduce noise; increase the distance between the inverter and the motor; suppress transient overvoltages; and reduce harmonics while improving the current waveform. DC reactors are primarily used to suppress the higher harmonics generated by inverters, and they are more effective than AC reactors in this regard