Because the frequency converter output voltage waveform is similar to the sine wave, but not the real sine wave. Its waveform contains a lot of harmonic components, especially the high-order harmonic will increase the output current of the inverter, causing motor winding heating, vibration and noise, accelerating insulation aging, and even may damage the motor; At the same time, harmonics of various frequencies will send different programs of radio interference to space, so it may lead to other electromechanical equipment misoperation.
Therefore, it is necessary to consider the distance between the central control room, the inverter and the motor when installing the inverter, so as to reduce the influence of harmonics and improve the stability of the control.
One,Definition of distance:
1. Short distance: the distance between inverter and motor is ≤20m;
2. Medium distance: the distance between inverter and motor is < GT; 20m, and ≤100m;
3. Long Distance: the distance between inverter and motor is < GT; 100m;
Two,the occasions on which the industrial sites are used:
1, short distance: Between the inverter and motor can be directly connected;
2, medium distance: between the inverter and motor can be directly connected, but the need to adjust the frequency of the inverter carrier to reduce harmonics and interference;
3,Remote: the inverter and the motor can be directly connected, not only need to adjust the frequency of the inverter carrier to reduce harmonics and interference, but also need to add the output AC reactor.
Three,In a highly automated factory:
In a highly automated plant, all equipment needs to be monitored and controlled in a central control room. Therefore, the signal of the inverter system should also be sent to the central control room.
1, short distance: that is, if the inverter installed in the central control room. Between the console and the inverter, can be directly connected, through 0 -5/10 V voltage signals and some switching signals to control. However, the high-frequency switching signal of the inverter electromagnetic radiation on the weak control signal will have some interference, so it is not necessarily beautiful and tidy, put the inverter in the central control room.
2. Medium distance: if the distance between the inverter and the central control room is far, the current signal of 4-20mA and some switches can be used as the control connection, if the distance is far, the RS485 serial communication can be used to connect;
3. Long Distance: the distance between inverter and central control room is more than 100m. At this point, the communication relay can be used to reach a distance of 1 km; if further, the need to use fiber optic connectors, up to 23 km.
With the communication cable connection, the multi-stage drive control system can be formed conveniently, and the master/slave and synchronous control requirements can be realized. Connecting with the popular fieldbus system will greatly increase the data conversion rate. The distance between the central control room and the converter cabinet is lengthened to shorten the distance between the converter and the motor so as to improve the system performance with a more reasonable layout.
Source: internet (for study only, intrusion and deletion)
