Application of frequency converter in permanent magnet direct drive ball mill

Ball mills are widely used in non-ferrous metal beneficiation, electricity, metallurgy, petroleum, petrochemical, municipal water supply, cement, pipelines and other industries.

Taking the non-ferrous metal beneficiation industry as an example, let's look at a gold mine process diagram, and we can see that the ball mill is an extremely important part of the entire process.

This sharing case comes from foreign customers.

The company used horizontal ball milling in the early stage of grinding. Mineral particles enter the ball mill for grinding. The material enters the first chamber  of the ball mill through the feeding device. The motor drives the cylinder to rotate, driving the steel balls in the chamber to collide with the material, bringing the steel balls to a certain height and then falling, which produces a heavy impact and grinding effect on the material.

Each compartment has steel balls of different sizes according to the production device. After the material in the first chamber is coarsely ground, it is sent to the second chamber through the partition, and the material is further ground through the flat lining plate and steel balls of the second chamber. The material ground to a certain particle size (referring to the particle size) is discharged through the discharging grate plate. Through the whole process of grinding, the ultra-fine grinding operation is completed, and then enters other processes for mineral processing.

Previously, the company mainly used belt conveyors for transportation. The traditional supporting model was asynchronous motors driving reducers. The equipment was large in size and occupied the space in the lanes. The gear oil used in the reducer was expensive and the amount was large. The subsequent maintenance was large and the pollution was large.

Compared with asynchronous motors, permanent magnet synchronous motors do not require reactive excitation current, so they have high efficiency, high power factor, large torque-to-inertia ratio, reduced stator current and stator resistance losses, and the rotor parameters can be measured and the control performance is good.

We have learned that permanent magnet synchronous motors have advantages over asynchronous motors in terms of improving efficiency, reducing losses, and improving controllability. When high-voltage frequency conversion is combined with permanent magnet synchronous motors, this advantage is further amplified.

(1) High efficiency: Due to the presence of permanent magnets, the rotor of a permanent magnet synchronous motor does not need to be excited, thereby reducing the energy loss of the motor.

(2) High-precision control: The rotor of a permanent magnet synchronous motor is synchronized with the magnetic field, so its operating speed is very stable and can be accurately controlled near the set value, making it suitable for applications that require high-precision control.

(3) Low noise: The rotor of a permanent magnet synchronous motor adopts a double-layer winding structure, which reduces the electromagnetic noise of the rotor, and its brushless design also reduces mechanical noise.

(4) High power density: Under the same volume, the output power of a permanent magnet synchronous motor is greater than that of an asynchronous motor, so a smaller and lighter motor design can be achieved.