In industrial applications, the installation distance between the frequency converter and the motor can be roughly divided into three categories: long distance, medium distance, and short distance. A distance of less than 20m is considered short distance, 20-100m is medium distance, and more than 100m is long distance.
Because the voltage waveform output by a frequency converter is not sinusoidal and contains a large number of harmonic components, high-order harmonics can increase the converter's output current, causing the motor windings to heat up, generate vibration and noise, accelerate insulation aging, and potentially damage the motor. Simultaneously, harmonics of various frequencies can emit varying degrees of radio interference into space, potentially causing malfunctions in other equipment. Therefore, it is desirable to place the frequency converter near the controlled motor. However, due to space limitations in the production environment, a certain distance is often required between the frequency converter and the motor. If the distance between the frequency converter and the motor is within 20 meters, they can be directly connected. For a medium-distance connection of 20 to 100 meters, the carrier frequency of the frequency converter needs to be adjusted to reduce harmonics and interference. For a long-distance connection of more than 100 meters, not only should the carrier frequency be appropriately reduced, but an output AC reactor should also be installed.
In highly automated factories, all control equipment can be monitored from a central control room. Signals from the frequency converter system must also be sent to the central control room. If the frequency converter is located in the central control room, the main control console and the frequency converter can be directly connected, controlled via 0-5/10V voltage signals and some switching signals. However, the electromagnetic radiation from the high-frequency switching signals of the frequency converter can interfere with weak current control signals, so it's not always aesthetically pleasing to place the frequency converter in the central control room. If the frequency converter is a little far from the central control room, a 4-20mA current signal and some switching signals can be used for control connection; if the distance is even greater, RS485 serial communication can be used; for further distances, communication relays can be used to achieve a distance of 1km; and with fiber optic connectors, distances up to 23km can be reached. Using communication cables, multi-stage drive control systems can be easily constructed, enabling master/slave and synchronous control requirements. Connecting with currently popular fieldbus systems will greatly improve data conversion rates. Extending the distance between the central control room and the inverter cabinet helps to shorten the distance between the inverter and the motor, allowing for a more rational layout to improve system performance.
In summary, when installing a frequency converter, it is necessary to comprehensively consider the distance between the central control room, the frequency converter, and the motor to minimize the impact of harmonics and improve the stability of control.
