Since the voltage waveform output by the frequency converter is similar to a sine wave rather than a true sine wave. Its waveform contains a large amount of harmonic components, especially high-order harmonics, which will increase the output current of the frequency converter, cause the motor windings to heat up, generate vibration and noise, accelerate insulation aging, and may even damage the motor. At the same time, harmonics of various frequencies will emit radio interference of different programs into space. Therefore, it may cause malfunctions of other electromechanical equipment.

Therefore, when installing a frequency converter, it is necessary to comprehensively consider the distances among the central control room, the frequency converter and the motor in order to minimize the influence of harmonics and improve the stability of control.

1.The definition of distance:

Short distance: The distance between the frequency converter and the motor is ≤20m.

Medium distance: The distance between the frequency converter and the motor is greater than 20m and less than or equal to 100m.

Long distance: The distance between the frequency converter and the motor is greater than 100 meters.

2. Occasions of industrial application sites:

Short distance: The frequency converter and the motor can be directly connected.

Medium distance: The frequency converter and the motor can be directly connected, but the carrier frequency of the frequency converter needs to be adjusted to reduce harmonics and interference.

Long distance: The frequency converter and the motor can be directly connected. Not only does it need to adjust the carrier frequency of the frequency converter to reduce harmonics and interference, but also an output AC reactor needs to be installed.

3. In a highly automated factory:

In highly automated factories, all the equipment needs to be monitored and controlled in the central control room. Therefore, the signal of the frequency converter system also needs to be sent to the central control room.

Short distance: That is, if the frequency converter is installed in the central control room. The console and the frequency converter can be directly connected and controlled through 0-5/10V voltage signals and some switch signals. However, the electromagnetic radiation from the high-frequency switching signals of the frequency converter can cause some interference to the weak current control signals. Therefore, it is not necessary to place the frequency converter in the central control room in a neat and tidy manner.

Medium distance: That is, the distance between the frequency converter and the central control room is a bit greater. A 4-20mA current signal and some switch quantities can be used for control connection. If the distance is longer, the RS485 serial communication method can be adopted for connection.

Long distance: That is, the distance between the frequency converter and the central control room is greater than 100 meters. At this point, a distance of 1 kilometer can be achieved by using the communication intermediate relay. If it is further away, optical fiber connectors need to be used, and the maximum distance can reach 23 kilometers. By using communication cables for connection, a multi-level drive control system can be conveniently formed, thereby achieving requirements such as master/slave and synchronous control. Connecting with the currently popular fieldbus system will greatly increase the data transformation rate. The extension of the distance between the central control room and the frequency converter cabinet is conducive to shortening the distance between the frequency converter and the motor, so as to improve the system performance with a more reasonable layout.