Influence of distance between inverter and motor on the system and preventive measures

1. In the field of industrial use, the distance between the inverter and the motor can be roughly divided into three types: source distance, middle distance and close distance. Within 20m for close distance, 20-100m for middle distance, and 100m for longer distance.

Because the inverter output voltage waveform is not sinusoidal, the waveform contains a large number of harmonic components, in which higher harmonics will increase the output current of the inverter, resulting in motor winding heating, vibration and noise, accelerated insulation aging, and may also be damaged Motors; At the same time, harmonics of various frequencies may transmit radio interference of different programs to the space, and may also cause misoperation of other devices. Therefore, it is desirable to place the inverter near the controlled motor. However, due to the limitation of production site space, there is always a certain distance between the inverter and the motor. If the distance between the inverter and the motor is within 20m, it can be directly connected with the inverter. For the medium distance between the inverter and the motor of 20m to 100m, the carrier frequency of the inverter needs to be adjusted to reduce harmonics and interference. However, for a long-distance connection between the inverter and the motor of more than 100 m, not only should the carrier frequency be moderately reduced, but an output AC reactor should also be installed.

2. In a highly automated factory, all control devices can be monitored in the central control room. The signals of the inverter system are also sent to the central control room. If the position of the inverter is in the central control, between the master console and the inverter, it can be directly Connection, control by 0-5/10V voltage signal and some switch signal. However, the electromagnetic radiation of the high-frequency switching signal of the inverter will cause some interference to the weak control signal, so it is not necessarily neat and tidy, and the inverter is placed in the central control room. If the frequency converter is far from the central control room, 4-20mA current signal and some switches can be used for control connection; if the distance is farther, you can use RS485 serial communication to connect; if you want to increase the distance, you can use The communication relay reaches a distance of 1km; if a fiber optic connector is used, it can reach a distance of 23km. By using a communication cable connection, multiple and drive control systems can be easily constructed to implement master/slave and synchronous control. Connecting with the currently popular fieldbus systems will greatly increase the data conversion rate. The extension of the distance between the central control room and the frequency converter cabinet helps to shorten the distance between the frequency converter and the motor, so as to improve the system performance with a more reasonable layout.

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