On the load properties of the back drive device of the decanter centrifuge

- Dec 12, 2020-

The speed regulating device installed at the small shaft end of the decanter centrifuge differential is called the back drive device. These devices are: eddy current brakes; hydraulic motors; asynchronous motors; mechanical overload protection devices. When the spiral lags behind the drum These devices are all at the expense of consuming centrifugal motor energy, and act on the small shaft with braking torque to achieve the purpose of adjusting the differential speed. For the small shaft, the back drive device is a negative load. In general frequency converter speed control In the system, the motor connected to the small shaft of the differential is in a regenerative state for a long time, running in the fourth quadrant, receiving mechanical energy from the centrifuge, and feeding back the energy of regenerative braking to the DC bus of the inverter, and then the braking resistor It is consumed. There are also domestic manufacturers using domestically-made inverters to apply the common DC bus AC frequency conversion technology to the decanter centrifuge, so that most of this part of the energy is recovered, and good social and economic benefits have been achieved. The promotion of this technology. The application is undoubtedly extremely meaningful, and this article discusses it.

1. Conducive to the realization of constant torque control: some materials, such as urban sewage, contain 60%-70% of organic matter, and the sedimentation is compressible, and the solid content is constantly changing, so that the screw pushing torque follows Due to the fluctuation of the feed flow rate and solid content rate, the electrical system is required to control the feed amount or differential speed in time according to the torque change, otherwise, it is easy to block the material.

2.Excellent energy-saving performance: When the spiral is lagging, the regenerated energy is sent to the DC bus of the auxiliary inverter. Because the DC bus of the main and auxiliary inverters are connected in parallel, the energy is inconvenient to pass through the main inverter and be used by the main motor.

3. Easy to deal with the accumulation of materials in the drum caused by emergencies.

4. Fast dynamic response: Some PID control systems often have overshooting phenomenon, and the transition process takes a long time, such as the eddy current brake speed control system, and the stability period can sometimes be as long as several minutes. The frequency conversion speed control system torque response time is only 150-200ms [3], the dynamic characteristics are significantly improved.