An energy-saving control method for using a high-voltage frequency converter in a large mining ball mill
By using the high-voltage frequency converter for startup and operation control and by using bus current acquisition to determine the state of the mixture, the startup current of large mining ball mills can be controlled and the working efficiency optimized. This solves the problems of startup current impact and mixture viscosity changes, and achieves energy-saving effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YOLICO ELECTRIC WUXI
- Filing Date
- 2026-03-23
- Publication Date
- 2026-05-26
AI Technical Summary
The existing equipment experiences a large current surge during startup, which can easily burn out the motor. It also experiences a large power grid surge, and the viscosity of the mixture inside the drum can cause unstable efficiency, requiring adjustments based on human experience.
The high-voltage frequency converter control method is adopted. Through start-up control and operation control, the internal algorithm of the frequency converter is used to collect the bus current to determine the state of the mixture and realize the optimal speed adjustment of the drum.
It achieves controllable starting current, reduces grid impact, improves drum working efficiency, and reduces energy consumption.
Smart Images
Figure CN122076574A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of energy-saving control technology, specifically relating to an energy-saving control method for using a high-voltage frequency converter in a large mining ball mill. Background Technology
[0002] Traditional grinding mill equipment mainly consists of a feeding device, a roller assembly, a transmission device, a belt-driven speed change device, a discharge device, and an electrical control cabinet with start / stop mechanisms. For example... Figure 1 As shown.
[0003] The working principle is as follows: The coarse ore to be ground is injected through the feed inlet, mixed with a certain proportion of water and grinding aids, typically steel balls or steel rods. Then, the motor drives the drum through a transmission shaft and adjustable gears for speed reduction, finally rotating via a belt for shock absorption. Inside the drum are grinding balls or rods. Under the action of centrifugal force and friction, the grinding balls are lifted to a certain height and fall in a cascading or precipitating manner, ultimately grinding the mixture of ore and water into a slurry-like fine powder, which then flows out through the discharge port.
[0004] Grinding mills typically operate at a fixed speed, determined by a pulley or gear reduction mechanism (or sometimes a hydraulic coupling). The rotational speed of the ball mill directly affects the movement of the grinding balls and materials, as well as the grinding process. At different speeds, the movement of the grinding stones and materials within the mill varies as follows: Figure 2 As shown: (a) Cascading state: When the rotational speed is low, the grinding stones and materials rise with the inner wall of the cylinder. When the inclination angle of the grinding stones and materials is equal to or greater than the natural inclination angle, they slide down the inclined plane and cannot form a sufficient drop. The grinding effect of the steel balls on the materials is very small, and the efficiency of the ball mill is very low. (b) Centrifugal state: If the rotational speed of the cylinder is very high, due to the centrifugal force, the material and grinding stones no longer detach from the cylinder wall and rotate with it. At this time, the grinding stones no longer have an impact effect on the material, and the grinding efficiency is even lower. The minimum rotational speed in this state is called the critical speed; (c) Dropping state: When the rotational speed of the cylinder is between the two mentioned above, the grinding stone is carried to a certain height and falls along a parabola, which has the greatest impact on the material at the bottom of the cylinder and the highest grinding efficiency. The rotational speed at this time is called the optimal working speed.
[0005] Existing equipment technology has several problems when used: 1. During the drum start-up process, because the drum is filled with ore, steel balls and water, the instantaneous current of the starting motor is very large. Although using soft starter and frequency converter equipment can alleviate this, the instantaneous large current can easily burn out the motor and also has a great impact on the power grid.
[0006] 2. During the operation of the drum, the viscosity of the mixture inside the drum will change during the grinding process. In order to keep the grinding efficiency at its best, the drum speed must be adjusted and kept as close as possible to the throwing (c) state.
[0007] The current production process mainly relies on experienced workers who can identify and adjust the speed by listening to the sound of the rollers, which has certain limitations. Summary of the Invention
[0008] To address the aforementioned technical problems, this invention provides an energy-saving control method for using a high-voltage frequency converter in a large mining ball mill. This method not only solves the problem of high current at startup but also determines the condition of the mixture inside the drum during operation and adjusts the speed for optimal drum efficiency.
[0009] The technical solution is as follows: an energy-saving control method for using a high-voltage frequency converter in a large mining ball mill, characterized by including a start-up control method and an operation control method, wherein the start-up control method includes the following steps: (1) When starting, the frequency converter makes the drum rotate in the forward direction. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the opposite direction due to the shift of the center of gravity and the action of gravity. (2) The frequency converter makes the drum reverse. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the positive direction due to the shift of the center of gravity. (3) The frequency converter makes the drum rotate in the forward direction. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the opposite direction due to the shift of the center of gravity and the action of gravity. (4) Repeat the above reverse and forward rotation steps. The drum swings back and forth with increasing amplitude until it approaches 90° and the direction is forward. Then the inverter ends the above swing mode and finally lets the drum run continuously in the positive direction.
[0010] Its further features are that X% is set to 50-100%, and the number of clockwise and counterclockwise rotations is odd and at least 3; The operation control method is as follows: the drum rotates at a critical speed n, n=42.4 / √D±△ω, where D is the inner diameter of the drum, and △ω is the speed value adjusted according to the collected bus current data of the frequency converter; when the collected data indicates that the material in the drum is in a cascading or centrifugal state, △ω is added or subtracted.
[0011] By adopting this invention, the drum is oscillating back and forth under the control of a frequency converter. The start-up control sequence and parameters that need to be set manually are designed into the application program of the frequency converter. The principle is to use potential energy to achieve energy saving, and the controllable start-up current can also reduce the harmonic impact of the current on the power grid. Furthermore, through the internal algorithm of the frequency converter, the working status of the mixed mineral material in the drum is identified by collecting the bus current of the frequency converter, thereby automatically adjusting the speed to achieve the best working efficiency. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of a traditional mill. Figure 2 This is a schematic diagram of the mill's operating state; Figure 3 This is a schematic diagram illustrating the reversed state of potential energy during the process of this invention; Figure 4 This is a schematic diagram illustrating the improvement of the starting current of the present invention; Figure 5 This is a flowchart of the startup process of the present invention; Figure 6 This is a schematic diagram showing the working states of different grinding machines and bus voltage data of the present invention; Figure 7 This is a diagram showing the bus current acquisition during the operation of this invention; Figure 8 This is a flowchart illustrating the adjustment process of the drum rotation state according to the present invention. Detailed Implementation
[0013] An energy-saving control method for using a high-voltage frequency converter in a large mining ball mill includes a start-up control method and an operation control method. The start-up control method includes the following steps: (1) During startup, the frequency converter makes the drum rotate forward. When the operating current rises to X% of the motor's rated current, the machine stops. The set value of X% is 50-100%. At this time, the liquid mixture inside the drum rotates in the opposite direction due to the shift of the center of gravity and the action of gravity, forming a reversing torque of approximately (distance R) * (mass M) * (potential energy G) between the center of gravity and the shaft. Figure 3 As shown; (2) The frequency converter makes the drum reverse. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the positive direction due to the shift of the center of gravity. (3) The frequency converter makes the drum rotate in the forward direction. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the opposite direction due to the shift of the center of gravity and the action of gravity. (4) Repeat the above reverse and forward rotation steps. The drum swings back and forth with increasing amplitude until it approaches 90° and the direction is forward. Then the inverter ends the above swing mode and finally lets the drum run continuously in the positive direction.
[0014] The number of clockwise and counterclockwise rotations is an odd number, such as 3, 5, 7, or 9.
[0015] like Figure 4 As shown, when X% is selected as 100% of the rated current, and the number of forward and reverse rotations is 3, the potential energy peak at startup is much lower than that of the traditional startup method, and the total energy is also much lower. The startup process is as follows: Figure 5 As shown.
[0016] The critical speed of a ball mill refers to the speed at which the grinding media (steel balls) just begin to rotate with the drum without detaching from the drum liner. The industry formula is: n = 42.4 / √D, where n is the critical speed in rpm and D is the inner diameter of the drum in meters.
[0017] The critical speed is an important parameter. Below this speed, the impact force of the steel balls is insufficient, resulting in poor grinding effect; while above this speed, the steel balls begin to roll along the cylinder wall, losing their impact effect, which will affect the working efficiency and service life of the ball mill.
[0018] However, because the mixture changes from coarse to fine particles during the grinding process, the viscosity changes, so the critical speed needs to be finely adjusted.
[0019] This invention uses bus current sampling data from a frequency converter to analyze and infer changes in the mineral mixture within the drum, thereby determining whether the rotational speed is operating at optimal efficiency.
[0020] The operation control method is as follows: The drum rotates at a critical speed n, n = 42.4 / √D ± Δω, where Δω is the speed value adjusted based on the collected inverter bus current data; when the collected data indicates that the material inside the drum is in a cascading or centrifugal state, Δω is increased or decreased. Based on the three working states of the ball mill—cascading (a), centrifugal (b), and cascading (c)—the data sampled from the inverter bus voltage are as follows: Figure 6 As shown.
[0021] The following example illustrates this: For a ball mill drum with a diameter of 3 meters, the critical speed n, calculated from the formula V=42.4 / √3, is 24.5 RPM (revolutions per minute), which is equivalent to 0.41 (revolutions per second). Generally, ball mills operate at 80-100% of their critical speed. Therefore, the operating speed range for a 3-meter diameter ball mill is 19.6 ~ 24.5 RPM (revolutions per minute), which is equivalent to 0.33 ~ 0.41 (revolutions per second).
[0022] The rotation period Td of the ball mill can be calculated from the intermittent peak values Imax and Imin of the bus current, i.e., Td = Imax - Imin; or the peak value ΔIp of the bus current can be taken as Td. Both methods can calculate the current operating speed of the drum. The bus voltage sampling rate fs of the frequency converter program is ≥ 10 times 1 / Td. Generally, the period of Tp is 100ms, and fs uses a sampling rate of 1kHz. Waveform acquisition points are as follows. Figure 7 As shown.
[0023] if: A Td value between 0.33 and 0.41 indicates that the machine is operating within the normal range of the drop-type operation, with the roller rotating at a critical speed n, where n = 24.5. If the Td value is less than 0.33, it indicates that the rotation speed is too low and the efficiency is too low. The speed can be increased appropriately. The drum rotates at the critical speed n, n=24.5+△ω; If the Td value is greater than 0.41, it indicates that the rotation speed is too high and has exceeded the critical speed, resulting in low efficiency. The speed can be appropriately reduced, and the drum rotates at the critical speed n, where n = 24.5 - Δω.
[0024] Where △ω is an open and configurable parameter value.
[0025] Based on the operating conditions, the frequency converter application automatically adjusts the speed of the ball mill, such as... Figure 8 As shown.
[0026] The method of the present invention is to use a high-voltage frequency converter in a large ball mill. Through the internal algorithm of the frequency converter, the working state of the mixed ore in the drum is identified by the potential energy-assisted start-up method and the frequency converter bus current is collected during the drum start-up and uniform speed operation, respectively. In this way, the speed can be automatically adjusted to achieve the best working efficiency.
Claims
1. An energy-saving control method for using a high-voltage frequency converter in a large mining ball mill, characterized in that, It includes a startup control method and a running control method. The startup control method includes the following steps: (1) When starting, the frequency converter makes the drum rotate in the forward direction. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the opposite direction due to the shift of the center of gravity and the action of gravity. (2) The frequency converter makes the drum reverse. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the positive direction due to the shift of the center of gravity. (3) The frequency converter makes the drum rotate in the forward direction. When the operating current rises to X% of the motor's rated current, the machine stops. At this time, the liquid mixture inside the drum rotates in the opposite direction due to the shift of the center of gravity and the action of gravity. (4) Repeat the above reverse and forward rotation steps. The drum swings back and forth with increasing amplitude until it approaches 90° and the direction is forward. Then the inverter ends the above swing mode and finally lets the drum run continuously in the positive direction.
2. The energy-saving control method for using a high-voltage frequency converter in a large mining ball mill according to claim 1, characterized in that, The X% setting is 50-100%, and the number of clockwise and counterclockwise rotations is odd and at least 3.
3. The energy-saving control method for using a high-voltage frequency converter in a large mining ball mill according to claim 1, characterized in that, The operation control method is as follows: the drum rotates at a critical speed n, n=42.4 / √D±△ω, where D is the inner diameter of the drum, and △ω is the speed value adjusted according to the collected bus current data of the frequency converter; when the collected data indicates that the material in the drum is in a cascading or centrifugal state, △ω is added or subtracted.