Variable frequency drive control schematic diagram
I. Main Circuit: The reactor's function is to prevent high-order harmonics generated by the frequency converter from returning to the power grid through the power input circuit and affecting other electrical equipment. Whether a reactor is needed depends on the frequency converter's capacity. A filter is installed at the frequency converter's output to reduce high-order harmonics. A filter should be installed when the distance between the frequency converter and the motor is long. Although the frequency converter itself has various protection functions, phase loss protection is not perfect. Circuit breakers in the main circuit provide overload and phase loss protection; their selection should be based on the frequency converter's capacity. The frequency converter's built-in overload protection can replace the thermal relay.
II. Control circuit: It has manual switching between power frequency and frequency conversion, so that the power frequency can be manually switched to operation when the frequency converter fails. Since the output terminal cannot be energized, the power frequency and frequency converter must be interlocked.
Variable frequency drive control schematic diagram
Determining the distance between the frequency converter and the motor, and the cable and wiring methods.
I. The distance between the frequency converter and the motor should be as short as possible. This reduces the cable's capacitance to ground and decreases sources of interference.
II. Shielded cables should be used for control cables, and shielded cables should be used for power cables, or the entire cable from the frequency converter to the motor should be shielded by conduit.
III. Motor cables should be routed independently of other cables, with a minimum distance of 500mm. Long-distance parallel routing of motor cables with other cables should also be avoided to reduce electromagnetic interference caused by rapid changes in the inverter's output voltage. If control cables and power cables cross, they should cross at a 90-degree angle whenever possible. Analog signal lines related to the inverter should be routed separately from the main circuit line, even within the control cabinet.
IV. For analog signal lines related to the frequency converter, shielded twisted-pair cables are preferred. For power cables, shielded three-core cables (with a larger specification than ordinary motor cables) should be used, or follow the frequency converter's user manual.
grounding of frequency converter
Proper grounding of the frequency converter is crucial for improving system stability and noise suppression. The lower the grounding resistance of the frequency converter's grounding terminal, the better. The cross-sectional area of the grounding wire should be no less than 4mm², and its length should not exceed 5m. The frequency converter's grounding should be separate from the grounding point of the power equipment; they cannot share a common ground. One end of the signal cable's shielding layer should be connected to the frequency converter's grounding terminal, while the other end should remain floating. The frequency converter and the control cabinet should be electrically connected.
Disclaimer: This article is a reprint. If it involves copyright issues, please contact us promptly for deletion (QQ: 2737591964). We apologize for any inconvenience.
