Brake State Monitoring Using Frequency Converter Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for monitoring the state of brakes in mechanisms controlled by frequency converters or electric motors, such as those in tower cranes, are unreliable and prone to delayed detection of abnormal states, especially in hydraulic brakes and multi-clamp systems, often requiring additional sensors or pressure switches that can malfunction.
Innovation Solution
A method that utilizes the torque information provided by frequency converters to check the state of the brake by comparing the torque supplied after a predefined time with predetermined minimum or maximum values, allowing for reliable and quick detection without additional components, and automatically stopping the motor if the brake is not open or closed correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensor is placed on the brake to detect its state, then the brake state can be monitored, but the device complexity increases and additional components are required
Solution Approach 1:
The frequency converter uses its own existing torque measurement capability to monitor brake state, making the system self-monitoring without requiring external sensors. The controller leverages data it already collects during normal operation to detect brake failures.
Solution Approach 2:
The frequency converter's torque measurement function, originally designed for motor control, is also used for brake state monitoring. This multi-functional use of existing hardware eliminates the need for dedicated brake sensors while maintaining monitoring capability.
2Reliability
If a temperature sensor is used to indicate brake state, then brake condition can be detected, but the detection is delayed due to thermal inertia and heating is slow
Solution Approach 1:
The patent replaces thermal-based detection with mechanical torque-based detection. Instead of measuring temperature changes that occur slowly, the system measures torque variations that occur immediately when brake clamps fail to open, providing instantaneous detection.
Solution Approach 2:
The system skips the slow thermal process and directly measures the mechanical effect (torque) that occurs immediately when brake failure happens. By measuring torque at a specific time after motor startup, the system detects brake state without waiting for thermal changes.
3Reliability
If additional sensors or pressure switches are added to monitor brake state, then monitoring capability is improved, but the device complexity and component failure risk increase
Solution Approach 1:
The frequency converter performs brake monitoring using its built-in torque measurement function, making the system self-diagnosing without requiring additional monitoring components. The existing controller infrastructure is leveraged for dual purposes.
Solution Approach 2:
The torque measurement capability, originally designed for motor control and speed regulation, is also used for brake state monitoring. This universal use of existing hardware eliminates the need for dedicated brake monitoring components.
Data Source
Figure 1~2
Figure 3
AI summary
The method involves controlling torque (C) provided by a frequency converter (9) or controller during starting or stopping of an electric motor (7). The torque is compared with preset reference torque value i.e. maximum permissible torque value, based on operation of a mechanism i.e. lifting winch (6), to provide a result indicating a state of brake (11) of mechanism after passage of predefined time corresponding to time required for opening or closing the brake. Unopened state of the brake is observed if the torque is greater than or equal to the value, and the motor is automatically stopped.