Ball Mill Drive System Torque Surge for Caking
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Solution Overview
Problem
Ball mills driven by slip-ring motors face challenges in detecting and resolving 'caking' or 'frozen charge' situations, where material solidifies and sticks to the inner walls, potentially causing damage upon restart, as existing systems like the 'Mill Safety Start System' only detect but do not automatically loosen caking.
Innovation Solution
A drive system for ball mills that includes a family of characteristic curves relating torque to motor parameters, with a switching element that abruptly switches between these curves to create a torque surge, allowing for automatic loosening of caking without complex control or regulation, using a switching element and additional resistor in the motor's supply line to induce a torque shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a slip-ring motor is used to drive the ball mill, then the drive system is simpler and cheaper, but the system cannot automatically loosen caking without complex control or regulation
Solution Approach 1:
The patent changes the electrical parameters of the slip-ring motor by switching between different characteristic curves (torque-speed relationships) to generate torque surges that loosen caking. This allows automatic caking resolution using standard slip-ring motors without complex control systems, resolving the contradiction between drive simplicity and automation capability.
2Productivity
If the drum is set in rotation when caking occurs, then the mill can resume operation, but the caking and attached grinding media may suddenly come off and damage the mill
Solution Approach 1:
The patent applies preliminary action by detecting caking conditions before resuming normal operation and automatically applying torque surges to loosen the caking first. This prevents the sudden release of caking that could damage the mill, while still enabling operation resumption.
3Extent of automation
If a ring motor is used with controller programming, then caking can be shaken loose automatically, but the system cannot be applied to slip-ring motors which are only controlled but not regulated
Solution Approach 1:
The patent creates a universal solution that works with standard slip-ring motors by utilizing their existing characteristic curves. The method can be applied to any slip-ring motor without requiring specialized regulated drives, greatly enhancing adaptability while maintaining automatic caking loosening capability.
4Reliability
If manual intervention is used to loosen caking by flooding or mechanical means, then caking can be resolved, but manual intervention and water addition are required
Solution Approach 1:
The patent implements self-service by enabling the ball mill drive system to automatically detect and resolve caking conditions through characteristic curve switching. The system serves itself without requiring manual intervention or water addition, eliminating operational complexity while maintaining reliable caking resolution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively loosens caking in approximately 80% of cases, eliminating the need for manual intervention and water or mechanical loosening, by automatically detecting caking and inducing a torque shock through abrupt changes in torque, thus preventing mill damage.
Implementation Method 1
there is also a jump in torque on the motor or the drum of the ball mill when switching over... The torque shock therefore causes the drum of the ball mill to be shaken
Data Source
Figure 1
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AI summary
In a drive system (10) for a ball mill (2) driven by a motor (12) with a slip-ring rotor, wherein the motor (12) is assigned a family of characteristics (36) relating the torque (M) of the motor to a further characteristic variable (D), the family of characteristics (36) has at least two different characteristics (40a-e, 42), and it includes a switching element (20) that switches over the drive system (10) abruptly between the two characteristics (40a-e, 42) when there is a constant value of the characteristic variable (D). In a method for operating a ball mill (2) with a drive system (10), a drum (6) of the ball mill (2) is moved out of a state of rest (R) when the first characteristic (40a-e) is activated; in the event of caking (34) in the drum (6) of the ball mill (2), it is moved until the caking (34) is in an inclined position (S1-2); actuation of the switching element (20) brings about switching over to the second characteristic (42).