In the industrial use site,Frequency changerThe distance from the motor installation can be roughly divided into three cases: source distance, medium distance and close distance. Within 20m is a short distance, 20-100m is a medium distance, and more than 100m is a long distance.

Because the output voltage waveform of the inverter is not sinusoidal, the waveform contains a large number of harmonic components, among which high order harmonics will increase the output current of the inverter, resulting in motor winding heating, vibration and noise, accelerate insulation aging, and may damage the motor; At the same time, harmonics of various frequencies will emit radio interference of different programs to space, and may also cause other equipment to misoperate. Therefore, it is hoped that the inverter is placed near the controlled motor. However, due to the space limitation of the production site, there is often a certain distance between the frequency converter and the motor. If the short distance between the inverter and the motor is within 20m, it can be directly connected with the inverter; For the medium distance connection between the frequency converter and the motor of 20m to 100m, the carrier frequency of the frequency converter needs to be adjusted to reduce harmonics and interference; For the long-distance connection between the inverter and the motor of more than 100m, not only the carrier frequency should be moderately reduced, but also the output AC reactor should be installed.

In highly automated factories, all control equipment can be monitored in the central control room, the signal of the frequency converter system is also sent to the central control room, if the location of the frequency converter is controlled in the central control, the total console and the frequency converter can be directly connected, through 0-510v voltage signals and some switching signals for control. However, the electromagnetic radiation of the high-frequency switching signal of the inverter will cause some interference with the weak current control signal, so it is not necessarily beautiful and neat, and the inverter is placed in the central control room. If the frequency converter is far away from the central control room, a 4-20ma current signal and some switching quantities can be used for control connections; If the distance is further, rs485 serial communication can be used to connect; If you want to extend the distance, you can use the communication intermediate relay to reach a distance of 1km; If the optical fiber connector is used, it can reach a distance of 23km. With the communication cable connection, it can be very convenient to form a multi-drive control system, so as to achieve master slave and synchronous control requirements. The connection with the current popular fieldbus system will greatly improve the data conversion rate. The extension of the distance between the central control room and the inverter cabinet is conducive to shortening the distance between the inverter and the motor in order to improve the system performance with a more reasonable layout.

In short, when installing the inverter, it is necessary to comprehensively consider the distance between the central control room, the inverter and the motor to minimize the influence of harmonics and improve the stability of the control.

Devil's 13 Electric is a non-regional joint-stock enterprise integrating scientific research, development, production and sales. Its business involves industrial control components, instrumentation, motor protection, frequency converter, soft starter and other fields. It is a high-tech enterprise with first-class scientific research and development capabilities. For more information, call 400-8236-775