Application of AU500 Series Inverter on Ball Mill

Introduction

For an extended period, industries such as chemicals, cement, and ceramics have commonly used ball mills for raw material grinding. These ball mills traditionally adopt a frequency-sensitive resistor voltage-drop starting method, leading to excessive material grinding, extended grinding cycles, low grinding efficiency, high unit product power consumption, substantial startup current, significant impact on equipment and the power grid, and challenging electrical equipment maintenance. This not only poses challenges for electrical technicians but also severely hinders rapid development in various industrial enterprises. To address these issues, the development of a ball mill with smooth startup, high grinding efficiency, large output, and low energy consumption—a variable frequency speed control system—became imperative.

Main Structure

A ball mill primarily consists of a transmission device, barrel device, feeding device, discharging device, and electrical control device.

Working Principle

A ball mill comprises feeding, discharging, rotating, and transmission parts (reducer, small gear, motor, and electrical control). In the ceramic industry, the horizontally placed barrel is divided by partitions (plates with many small holes—screen plates) into 2 to 4 grinding chambers. Each chamber contains grinding bodies of a certain shape and size. When the barrel rotates, materials and grinding bodies are lifted to a certain height under the action of friction and centrifugal force. Then, under the force of gravity, they fall along an approximate parabolic trajectory, impacting and grinding another portion of the material at the bottom of the barrel. This results in a certain axial movement that promotes uniform grinding and mixing of materials. Ball mills can be categorized into dry and wet grinding based on the process.

Basic Electrical Control Device

Most ball mills use a frequency-sensitive resistor as a starting device, which, during the moment of startup, imposes a significant impact on the power grid. Additionally, the required torque decreases during operation, providing ample energy-saving potential.

Retrofit Scheme

Considering the existing issues in the original condition and the requirements of the production process, the retrofitted ball mill system should meet the following criteria:

Sufficient starting torque to meet the high load capacity of the ball mill, ensuring stable motor operation under variable frequency conditions and guaranteeing constant power characteristics.

Utilization of a variable frequency speed control system to transform the original ball mill drive system, ensuring normal operation at low speeds, facilitating normal process control, extending the lifespan of the ball mill and the motor, and reducing maintenance.

The retrofitted equipment should feature automatic control, manual/power frequency switching, and fault auto-switching functions, overcoming the voltage rise caused by the large inertia of the ball mill and effectively ensuring normal equipment operation.

Inverter Selection

Following the aforementioned principles, the Ausenist AU500 series ball mill dedicated inverter is selected to meet the specified operating conditions.

Characteristics of the Inverter

Satisfies the characteristics of low-speed operation and large starting torque of the ball mill, achieving continuously adjustable operating speeds. The motor exhibits no impact current during startup, ensuring sufficient starting torque and comprehensive protection features. This guarantees the quality of process control and saves maintenance costs.

Some customers have attempted retrofitting with other brands' general-purpose inverters, but the results were not ideal. Ausenist Electrical, drawing on years of retrofitting experience, utilizes the AU500 series ball mill dedicated inverter's internally set V/F curve to optimize startup and acceleration performance. This custom V/F curve is tailored to the working characteristics of the ball mill itself, proving to be operationally stable and reliable in practice.