Roller Mill Drive Segmentation for Power Fluctuation Control
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Solution Overview
Problem
Roller mills experience significant power fluctuations and high energy requirements due to differences in grinding roller power consumption and transmission ratios, leading to increased costs for drive train components and potential system instability.
Innovation Solution
Implementing a load balancing control system using power equalization controllers that adjust the rotor current of asynchronous motors to maintain consistent power levels across drives, reducing the power requirements of control devices and allowing for smaller motors and simpler gear systems, with control devices capable of operating at lower voltages and lower power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If individual grinding rollers are driven separately with full-power converters to maintain synchronous operation, then speed synchronization is improved, but drive train costs increase significantly
Solution Approach 1:
The drive system is segmented into a main drive for the grinding table and individual roller drives. Each roller is equipped with a separate drive unit that can operate independently, allowing synchronized operation through control coordination rather than requiring all rollers to be driven by a single complex drive train. This segmentation enables the use of simpler, lower-power converters for each roller while maintaining overall system synchronization.
Solution Approach 2:
The control system implements feedback mechanisms where the actual speeds of individual rollers are monitored and compared against the grinding table speed. Based on this feedback, the control units adjust the roller drive speeds dynamically to maintain synchronization. This feedback-based coordination allows the system to achieve speed synchronization without requiring overly complex drive train components.
2Reliability
If grinding table is driven by a single powerful motor to ensure uniform power transmission, then power transmission reliability is improved, but motor size and cost increase
Solution Approach 1:
The single powerful motor drive is segmented into multiple smaller drive units, with one main drive for the grinding table and additional individual roller drives. This distributes the power transmission function across multiple components, allowing the use of smaller motors while maintaining reliable power transmission through coordinated operation of all drive units.
Solution Approach 2:
The system incorporates redundancy by equipping individual rollers with their own drive units. If one drive unit fails or experiences problems, the other drive units can compensate and maintain operation, providing a cushioning effect that protects against complete system failure. This redundancy allows the use of smaller individual motors rather than requiring one oversized motor with no redundancy.
3Use of energy by moving object
If high-power converters are used for all drives to handle power fluctuations, then power fluctuation compensation is improved, but system cost increases
Solution Approach 1:
Instead of equipping all drives with high-power converters, the system applies different converter power levels based on local requirements. The main grinding table drive receives a full-power converter to handle significant power fluctuations, while individual roller drives receive lower-power converters since their power fluctuation requirements are smaller. This local differentiation optimizes the balance between power fluctuation compensation and system cost.
Solution Approach 2:
The system applies partial action by providing power fluctuation compensation capabilities selectively rather than uniformly across all drives. The main drive receives full compensation capability, while roller drives receive proportional compensation appropriate to their smaller power requirements. This partial approach achieves sufficient power fluctuation management without the excessive cost of high-power converters on every drive unit.
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
This approach reduces energy fluctuations, decreases control device costs by up to 70%, enables the use of smaller and more efficient motors, and provides redundancy to prevent system interruptions in case of drive failure, while maintaining high efficiency and reducing the need for complex measurement technology.
Implementation Method 1
The motor torque is influenced by directly influencing the rotor current
Data Source
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AI summary
The roller mill according to the invention comprises a grinding table (10), at least one grinding roller (11, 12) and at least two motors (drives) (13, 14) with stator and rotor windings for driving the roller mill and is equipped with at least one control device (20, 21) for regulating the motor torque of at least one drive. The control device is connected to the rotor winding (13a, 14a) of at least one drive for the purposes of influencing the rotor current. Further protected is a method for size reduction of ground material using such a roller mill.