Safety Switch Transformer Test Signal Fault Detection
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Solution Overview
Problem
Current safety switch devices face challenges in reliably detecting faults in switching elements, such as welded relay contacts and transistor breakdowns, which can lead to short circuits, and require complex redundancy and additional safety mechanisms, increasing costs and complexity.
Innovation Solution
A safety switch device with two serially connected controllable switching elements and a safety circuit using a transformer to provide a test signal, allowing for continuous and reliable monitoring, and optionally incorporating an optocoupler for state verification, enabling detection of faults and reducing component count and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple channel redundancy is implemented to detect faults, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent introduces a transformer as an intermediary component to couple the control circuit with the safety circuit. This transformer enables fault detection functionality while maintaining galvanic isolation, thereby achieving improved reliability without proportionally increasing device complexity through direct circuit connections
Solution Approach 2:
The patent replaces mechanical test button presses with an automated electrical test signal generation system. The control circuit automatically generates test signals through the transformer to verify switching element states, eliminating the need for manual intervention and reducing operational complexity
2Reliability
If safety relevant relays with force guided contacts are used, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical force-guided contact structures with an electrical test signal-based monitoring system. By injecting test signals through the transformer and detecting responses, the system achieves contact state verification without requiring complex mechanical guiding mechanisms or specially designed safety relays
Solution Approach 2:
The switching elements themselves are utilized to conduct the test signals through their contacts. The existing relay contacts serve dual purposes: normal load switching and fault detection pathways, eliminating the need for separate monitoring contacts or additional safety relay mechanisms
3Reliability
If capacitors or optocouplers are used for decoupling, then galvanic isolation is achieved, but test signal transmission becomes unreliable
Solution Approach 1:
The transformer serves as an intermediary that enables reliable AC test signal transmission while maintaining galvanic isolation between circuits. Unlike capacitors or optocouplers that may block or attenuate test signals, the transformer's magnetic coupling mechanism efficiently transmits the test signals needed for fault detection
Solution Approach 2:
The patent utilizes the transformer's ability to transfer AC signals while blocking DC components. By changing the signal type to AC for testing purposes, the system achieves both galvanic isolation and reliable signal transmission, as the transformer couples AC test signals effectively while preventing DC load currents from interfering with the isolation
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 provides a reliable and cost-effective method for detecting faults in switching elements, ensuring safe operation, extending relay life, and reducing the number of components and space requirements, while allowing for flexible and continuous testing.
Implementation Method 1
The test signal is provided to the safety circuit via a transformer that functions as decoupling means to galvanically decouple the control circuit from the load circuit
Data Source
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AI summary
A safety switch device (100; 200; 300; 400) configured to perform at least one of connecting a load (132) to a power supply (134) and disconnecting the load (132) from the power supply (134) is provided. The safety switch device (100; 200; 300; 400) comprises a first set of two serially connected controllable switching elements (120a, 120b); a safety circuit (110) to verify a switching state of the first set of two switching elements (120a, 120b), wherein each switching element (120a, 120b) of the first set of two switching elements (120a, 120b) is configured as a toggle; a control circuit (180) configured to provide a test signal to the safety circuit (110); and decoupling means configured to galvanically decouple the load circuit (130) from the control circuit (180). The decoupling means comprise a transformer (112), and the control circuit (180) comprises a transformer driver (150) configured to provide the test signal to the safety circuit (110) via the transformer (112).