The voltage waveform output by the inverter is only similar to a sine wave, not a true sine wave, and contains a large number of harmonic components.

As we all know, high-order harmonics will increase the output current of the inverter, cause heating of the motor winding, generate vibration and noise, accelerate insulation aging, and even damage the motor. At the same time, harmonics of various frequencies will transmit radio interference of different programs into space, which may cause misoperation of other electromechanical equipment.

Therefore, when installing the inverter, the inverter brand needs to comprehensively consider the distance between the central control room, the inverter and the motor to minimize the impact of harmonics and improve control stability.

（1） Definition of distance:

1. Short distance: The distance between the inverter and the motor is ≤ 20m;

2. Medium distance: The distance between the inverter and the motor is >20m≤100m;

3. Long distance: The distance between the inverter and the motor is >100m;

（2） Industrial land:

1. Short distance: The inverter and the motor can be directly connected;

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

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

（3）In a highly automated factory:

In a highly automated factory, all equipment needs to be monitored in a central control room. Therefore, the signal of the inverter system should also be sent to the central control room.

1. Proximity: If the inverter is installed in the central control room. The console can be directly connected to the inverter, controlled by 0-5/10V voltage signal and some switch signals. However, the electromagnetic radiation of the high-frequency switch signal of the inverter brand will cause certain interference to the weak current control signal, so it does not have to be beautiful and neat. Place the inverter in the central control room;

2. Medium distance: That is, the inverter of the inverter brand is far away from the central control room, and 4-20mA current signal and some switch quantity can be used for control connection; if the distance is long, RS485 serial communication connection can be used;

3. Long distance: That is, the distance between the inverter brand and the central control room is greater than 100m. At this time, the communication intermediate relay can reach a distance of 1km; if the distance is far, a fiber optic connector should be used, and the longest can reach 23km.

The inverter brand adopts communication cable connection, which is convenient for forming a multi-level drive control system to meet the requirements of master/slave and synchronous control. Connection with the popular fieldbus system will greatly improve the data conversion rate. Extending the distance between the central control room and the inverter cabinet is conducive to shortening the distance between the inverter and the motor, thereby improving system performance and making the layout more reasonable.