1.Introduction

In China's ceramic industry, ball mills are used in large quantities and are indispensable important production equipment for material crushing. The ball mill generally has a large power. The system adopts simple power frequency control, requires long grinding cycle, low grinding efficiency, easy over-grinding of materials, and large power consumption per unit product, thus becoming one of the largest power-consuming devices in the ceramic industry. . At the same time, the starting current of the system is large, which has a great impact on the equipment and the power grid, resulting in a large maintenance of mechanical equipment. With the rapid development of frequency conversion speed regulation technology, frequency conversion speed regulation has been widely used in ceramics, cement and metallurgy industries. Practice has proved that the ball mill adopts frequency conversion control and energy saving effect is remarkable, which can create very good economic benefits for the enterprise. Taking SINCR C500 series inverter as an example, this paper introduces a frequency conversion control application scheme of ball mill.

2. Process introduction

2.1. The ball mill is mainly composed of a transmission device, a cylinder device, a feeding device, a discharging device and an electric control device. When the equipment is running, the electric motor is driven by the electric control device, and then the reduction gear of the reducer and the surrounding large wheel are used to drive the cylinder device to rotate. The material and the grinding body contained in the cylinder device are lifted to a certain height under the action of the centrifugal force and the friction force generated during the rotation, and then fall along the trajectory of the approximate parabola to impact and grind another part of the material at the bottom of the cylinder, and generate A certain axial operation causes the material to be ground and mixed evenly. The finished material is finally removed by the unloading device for the next process.

Technical indicators:

■The ball mill has large fluctuations in the running process, requiring the inverter to have over-current, overload and current limiting functions;

■ When the ball mill starts, the load is very heavy, and it is required to move the ball mill to any position by jogging;

■ In the case of the best ball grinding effect, a large degree of power saving.

2.2. In the ball mill, the movement state of the grinding body is related to the rotation speed of the cylinder and the friction factors of the grinding body and the inner wall of the cylinder. The movement state of the grinding body in the cylinder can be basically divided into:

a. sloping motion state: when the ball mill speed is low, all the grinding bodies can be regarded as a loose “clump”, and the “clump” interface is continuously upwards along the rotation direction as the cylinder rotates. Oblique, forming a slope. When the inclination angle of the slope reaches the natural angle of repose of the grinding body, the grinding body will roll down along the slope under the action of gravity or the like to form a sloping motion, as shown in the following figure. In the sloping motion, the material is mainly pulverized under the impact and grinding action caused by the relative motion of the grinding body.

b. Drop motion state: When the rotation speed of the ball mill is high, the grinding body will fall down like a projectile after the cylinder rises to a certain height. In the case of the throwing motion, the material is mainly thrown in the grinding body. The impact of the impact and the partial grinding action are shredded.

c. Centrifugal motion state: When the rotation speed of the cylinder is too high, due to the centrifugal force, the grinding body is “attached” on the inner wall of the cylinder and rotates together with the cylinder without being thrown away. In the centrifugal movement, The abrasive body no longer impacts and grinds the material, and the material is not crushed.

3. Control plan

According to the problems existing in the original working conditions of the ball mill and the production process and process characteristics, the system control scheme using SINCR C500 series inverter is designed as follows:

The main motor is driven by a vector inverter. The built-in optimized control program automatically adjusts the parameters of the motor during operation according to the real-time running load of the ball mill to optimize the shaft power of the motor. The system speed can be set to the automatic adjustment mode according to the change of the ball milling process conditions, which can effectively save energy while ensuring the working efficiency of the ball mill.

4. Program features and advantages

4.1. After the ball mill uses the frequency conversion speed regulation, the soft start of the system is realized. The starting current is greatly reduced, which is 3 to 5 times smaller than the previous power frequency control, eliminating the impact at the start, prolonging the service life of the mechanical components, reducing the maintenance and maintenance costs of the equipment, and reducing the power grid and Impact of peripheral equipment;

4.2. Using the frequency conversion vector speed control technology to drag, meet the characteristics of the ball mill low speed operation and large starting torque, and effectively guarantee the control technology of the system;

4.3. It is convenient to set the grinding time, grinding time and automatic stop function through the inverter to make the operation more intelligent and humanized;

4.4, energy saving effect can generally reach 10% to 15%;

4.5. The system has perfect protection functions such as phase loss, short circuit, over voltage and over current, and can also be installed with mains/energy saving switching function to ensure stable operation of the equipment.

5. Conclusion

This paper introduces a variable frequency drive scheme of ball mill based on SINCR C500 inverter. This scheme realizes the soft start of the system, effectively guarantees the system control process and improves the work efficiency, and the energy saving effect is remarkable, and the service life of the system is effectively extended. , reducing the amount of equipment maintenance, and achieving good economic benefits for customers. Practice has proved that the program has a very broad application prospect in the ceramic industry, and has been successfully applied to the system of multiple ball mill frequency conversion transformation.