Hybrid Safe Brake Switching for SIL3 Elevator Control
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Solution Overview
Problem
Elevator systems require SIL3 certified safe brake control, but existing solutions with SIL3 monitoring circuitry incur high hardware and cost burdens.
Innovation Solution
A system and method involving a semiconductor switch and a safety relay or contactor with normally closed contacts, where the semiconductor switch is electrically closer to the power source and opens before the electromechanical device, allowing for separate testing and reducing the need for complex SIL3 monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SIL3 monitoring circuitry is used for safe brake control, then safety reliability is improved, but hardware complexity and cost increase
Solution Approach 1:
The patent segments the brake control system into two independent switching stages: a semiconductor switch (first switch) for primary control and an electromechanical switch (second switch) for final circuit interruption. This segmentation allows each component to perform its function independently, achieving SIL3 safety requirements without requiring complex integrated monitoring circuitry. The semiconductor switch handles normal operation and testing, while the electromechanical switch provides the certified safety function.
Solution Approach 2:
The patent introduces a test signal as an intermediary element that enables verification of the semiconductor switch functionality without requiring complex monitoring circuitry. The test signal can be applied to the coil of the electromechanical switch to activate it and verify the brake engagement, providing a simple yet effective testing mechanism that reduces hardware complexity while maintaining safety reliability.
2Speed
If a semiconductor switch is used for brake control, then response speed and control precision are improved, but testing complexity increases
Solution Approach 1:
The patent implements preliminary testing capability by designing the system to allow test signals to be applied before normal operation. The semiconductor switch can be tested by activating the electromechanical switch through its coil, verifying the brake engagement function beforehand. This preliminary action ensures the system is ready for operation without requiring complex real-time monitoring during actual brake operations.
Solution Approach 2:
The system enables self-testing functionality where the electromechanical switch serves dual purposes: normal brake activation and testing of the semiconductor switch circuit. By applying a test signal to the coil, the system can verify its own functionality without external testing equipment, reducing testing complexity while maintaining fast response characteristics of the semiconductor switch.
3Reliability
If the electromechanical switch is placed electrically closer to the power source, then switching reliability is improved, but the ability to test the semiconductor switch independently is reduced
Solution Approach 1:
The patent segments the electrical circuit into distinct sections with the semiconductor switch positioned between the power source and the electromechanical switch. This segmentation creates independent testable sections: the semiconductor switch can be tested by applying signals to its gate while the electromechanical switch remains in its normal state. The electromechanical switch maintains its reliable position near the power source while the semiconductor switch's positioning enables independent testing through its gate control terminal.
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 configuration ensures safe brake control with reduced hardware and cost, while enabling effective testing of the semiconductor switch without affecting the electromechanical device, optimizing for SIL3 applications.
Implementation Method 1
a semiconductor switch electrically interposed between the power source and the brake element
Implementation Method 2
an electromechanical switch electrically interposed between the semiconductor switch and the brake element
Implementation Method 3
the brake element is configured to prevent rotation of a motor for raising or lowering an elevator car and includes a brake coil
Data Source
AI summary
An elevator control system for safe brake control (SBC) operation is provided, including a brake element, a power source for operating the brake element, a semiconductor switch electrically interposed between the power source and the brake element, and an electromechanical switch electrically interposed between the semiconductor switch and the brake element.