Motor-Operated Crane Drive Emergency Braking Control
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Solution Overview
Problem
Motor-driven crane drives experience excessive peak loads during emergency stops, leading to gear unit damage due to the rapid engagement of safety brakes, which can shorten the service life of the gear unit.
Innovation Solution
A method where an emergency stop signal triggers both the safety brake on the slower-rotating side of the gear unit and electric braking of the motor, generating a torque opposite to the motor's rotation to reduce the inert mass and peak load on the gear unit, utilizing regenerative converters to feed kinetic energy back into the grid or convert it into thermal energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the safety brake is rapidly engaged during emergency stop, then the load is stopped quickly, but the gear unit experiences excessive peak loads that can damage it
Solution Approach 1:
The motor is switched to generator mode before the safety brake is fully engaged during emergency stop. This preliminary action allows the motor to absorb kinetic energy and generate braking torque, reducing the peak load on the gear unit when the safety brake engages. The control system detects the emergency stop signal and immediately switches the motor operation mode, ensuring the motor contributes to braking before the mechanical brake takes full effect.
Solution Approach 2:
The motor acts as an intermediary between the load and the safety brake during emergency stopping. By switching to generator mode, the motor provides a intermediate braking mechanism that absorbs energy and reduces the shock load transmitted to the gear unit. This intermediary action smooths the transition and protects the gear unit from excessive peak loads while still achieving rapid stopping through the combined effect of motor braking and safety brake engagement.
2Strength
If the motor inert mass is reduced during emergency stop, then the peak load on the gear unit is reduced, but the braking distance may increase
Solution Approach 1:
The motor maintains continuous useful action during emergency stop by switching to generator mode. Instead of simply disconnecting the motor (which would create a gap in braking action), the motor continues to provide braking torque through electromagnetic generation. This continuous action ensures smooth deceleration without interruption, maintaining short braking distance while simultaneously reducing peak loads on the gear unit by avoiding inertial shocks.
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 significantly reduces the load on the gear unit during emergency stops, minimizing damage and allowing for smaller gear unit designs, resulting in economic advantages and increased drive availability.
Implementation Method 1
electric braking of the motor, generating a torque opposite to the motor's rotation
Implementation Method 2
utilizing regenerative converters to feed kinetic energy back into the grid
Implementation Method 3
or convert it into thermal energy
Data Source
AI summary
The invention relates to a motor-operated crane drive in which a more rapidly rotating motor (1) drives a more slowly rotating cable drum (3) via a transmission (3). A safety brake (5) is arranged on the more slowly rotating side of the transmission (2). A signal that is used for actuating the safety brake (5) is utilized for initiating an electrical deceleration of the motor (1).