What is the max length of the cable from inverter to the motor?

The voltage waveform output from the inverter is similar to a sine wave,but never a real sine wave. Its waveform contains a large number of harmonic components, especially the high harmonics will make the inverter output current increase, resulting in motor winding heating, vibration and noise, accelerate the insulation aging, and may even damage the motor.

At the same time, a variety of frequency harmonics will be emitted to the space of the different procedures of radio interference, it may lead to other electro mechanical equipment malfunction.

Therefore, it is necessary to comprehensively consider the distance between the central control room, inverter and motor when installing the inverter to minimise the impact of harmonics and improve the stability of control.

(i) Definition of distance:

1. Close distance: the distance between the inverter and the motor ≤ 20m;

2. Medium distance: the distance between the inverter and the motor >20m, and ≤100m.

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

(ii) The occasion of industrial use site:

1. Close distance: inverter and motor can be directly connected.

2. Middle distance: inverter and motor can be directly connected, but need to adjust the carrier frequency of inverter to reduce harmonics and interference.

3. Long distance: inverter and motor can be directly connected, not only need to adjust the carrier frequency of the inverter to reduce harmonics and interference but also need to add the output AC reactor.

(iii) In highly automated factories:

In highly automated factories, all equipments need to be monitored and controlled in the central control room. Therefore, the signal of the inverter system should also be sent to the central control room.

1. Close distance: the inverter is installed in the central control room. The control center and the frequency converter can be directly connected through the 0-5/10V voltage signal and some switching signals for control. However, the inverter's high-frequency switching signals of electromagnetic radiation on the weak control signals will produce some interference.

2. Medium distance: If the frequency converter and the central control room is a liitle far , you can use 4-20mA current signals and some switching for the control of the connection or use RS485 serial communication to connect;

3. Long distance: the distance between the frequency converter and the central control room is greater than 100 m.

You can use the communication intermediate relay to achieve a distance of 1km;

If more far, you need to use the optical fibre connector to reach the farthest 23km.

The use of communication cable connection, can easily constitute a multi-stage drive control system, so as to achieve the master / slave and synchronous control requirements.

Connection with the currently popular fieldbus system will make the data conversion rate greatly improved.

The extension of the distance between the central control room and the inverter cabinet will help to shorten the distance between the inverter and the motor in order to improve the system performance with a more reasonable layout.