The permanent magnet direct drive ISA mill uses a special frequency converter with a low-speed, high-torque permanent magnet motor to directly drive the mill equipment, removing the reducer. It has the advantages of compact structure, large starting torque, high efficiency, stable operation, high reliability, low noise, easy installation, and maintenance-free. It has a very high technical level and promotional value.
The equipment has a good fine grinding effect, and qualified products can be discharged only by open-circuit grinding. The grinding media and mineral particle sizes are radially distributed from the inner wall of the mill axial cylinder from small to large, forming a "velocity gradient" in the radial direction, "large balls for large particles, small balls for small particles", and qualified particle sizes move forward in the near-axis area, basically not participating in grinding, effectively reducing over-grinding and achieving selective grinding. At the same time, the mill adopts internal centrifugal classification and open-circuit grinding, replacing the external cyclone that other grinding equipment must rely on. The process is simple, the footprint is small, the infrastructure investment is small, the operation is convenient, and the maintenance is simple. A product separator is installed at the discharge end of the ISA mill. Qualified products are discharged from the mill from the central area, and the media and particles that do not meet the particle size requirements are returned from the edge of the cylinder for further grinding, achieving the effect of open-circuit grinding and closed-circuit classification, greatly simplifying the production process.
The customer originally planned to use a high-voltage asynchronous motor as the power source for the mill, and to perform frequency conversion speed regulation by equipping it with a 6KV frequency converter and a matching reducer. In this drive mode, there are many defects such as low transmission efficiency, severe mechanical wear, high power consumption, high failure rate, large space occupation, high operating noise, lubricating oil pollution, and heavy equipment maintenance workload.
The ISA mill permanent magnet direct drive system uses a special low-speed, high-torque permanent magnet direct drive motor to directly drive the mill drive shaft. The rotor is excited by permanent magnet materials to achieve low-speed, high-torque power transmission, and the motor is controlled by a special frequency converter for high-voltage synchronous motors, eliminating the reducer. The change in transmission mode, the removal of the reducer, simplifies the mill's transmission chain, reduces the maintenance cost of the reducer, removes the intermediate links, and improves the overall transmission efficiency of the mill.
2.1 In terms of improving transmission efficiency and reducing mechanical loss, the ISA mill has a comprehensive power saving rate of 20%, of which the permanent magnet motor active power saving rate is 18%, the efficiency power saving rate is 3%, and the reducer mechanical loss power saving rate is 3%. The annual electricity saving is 1.8816 million kWh, and the electricity cost saving is 1.317 million yuan.
2.2 In terms of reducing the occupied space, the space occupied by the reducer can be removed and the space occupied by the motor can be reduced by 2520mm.
2.3 In terms of frequency converter application, according to the unique characteristics of permanent magnet synchronous motor, the speed sensorless vector control technology of permanent magnet synchronous motor is realized, which can realize the intelligent identification of the initial position of the rotor of permanent magnet synchronous motor, large torque starting, high-precision speed control and other functions.
ISA mill control system adopts PLC centralized control with industrial computer remote monitoring, with local control and remote industrial control system remote control mode, and has remote control and remote diagnosis functions. The control system integrates the feeding system and the discharging system. At the same time, combined with a permanent magnet motor and frequency converter online monitoring, the automation and intelligence of the overall system of the ISA mill are realized.