Safety Switch Relay Architecture for Air Gap Compliance
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Solution Overview
Problem
Existing safety switches for critical loads lack a reliable mechanism to ensure a minimum predefined air gap, which is crucial for safe operation and compliance with European norms like EN 50205, especially under varying voltage conditions.
Innovation Solution
A monitoring and control system with a safety switch comprising two groups of relays connected in series and parallel configurations, along with a controller that uses subcontrollers and programmable logic devices to ensure that contacts remain closed with a minimal air gap, and activates or releases relays based on signal verification from multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If normal relays are used for switching safety critical loads, then the device complexity is reduced, but the reliability of maintaining a minimum predefined air gap cannot be ensured
Solution Approach 1:
The system divides the relay configuration into two independent groups (first group with relays 1010, 1080 and second group with relays 1110, 1180), each group containing multiple relays with switching contacts connected in parallel. This segmentation ensures that if one relay fails, the other relays in the same group and the other group maintain the required air gap, thereby improving reliability while managing complexity through structured division
Solution Approach 2:
The patent implements a redundant relay architecture where multiple relays are configured in parallel within each group, and two groups are connected in series. This beforehand cushioning ensures that the minimum predefined air gap is maintained even if one or more relays fail, as the redundant relays provide a backup path that preserves the safety distance required by EN 50205 type A norms
2Reliability
If multiple relays are configured to ensure minimum air gap, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple relays into two functional groups where the first sets of switching contacts from both groups are connected in series, and the second sets are connected in series. This merging approach consolidates the control logic while maintaining redundancy, as the series connection ensures that all relays must be activated simultaneously to close the circuit, simplifying the control requirement while preserving safety
Solution Approach 2:
Each relay is equipped with read back contacts that provide feedback to the control system about the actual state of the relay contacts. This feedback mechanism allows the controller to verify whether the minimum air gap is being maintained and to detect any relay failures, thereby managing system complexity through automated monitoring rather than requiring complex manual verification systems
3Reliability
If sequential opening of contacts is implemented, then the reliability is improved, but the operation time increases
Solution Approach 1:
The controller implements sequential opening of relay contacts in a controlled periodic manner during disconnection. Instead of opening all contacts simultaneously, the controller opens contacts of the first group and then contacts of the second group in sequence. This periodic action ensures that at least one set of contacts remains closed during the transition, maintaining the circuit until the sequential opening is complete, thereby improving reliability while managing the time loss through efficient sequencing
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 system provides high reliability and compliance with safety norms by ensuring a minimal air gap of 0.5 mm, allowing safe operation under different voltage conditions and reducing the complexity and cost of load switches.
Implementation Method 1
at least two groups of relays, wherein each group comprises at least two relays having respectively a first set of switching contacts and a second set of switching contacts, the first set of switching contacts and the second set of switching contacts of each relay are actuated simultaneously by an actuator
Data Source
Figure 1
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AI summary
The present invention concerns a monitoring and control system (1) comprising: a safety switch (5) including: a first input terminal (7a) and a second input terminal (7b) adapted to be connected to a power supply, a first output terminal (9a) and a second output terminal (9b) adapted to be connected at least one load (3), and at least two groups of relays (1000, 1100), wherein each group comprises at least two relays (1010, 1080; 1110, 1180) having respectively a first set of switching contacts (1012, 1082; 1112, 1182) and a second set of switching contacts (1014, 1084; 1114, 1184), the first set of switching contacts and the second set of switching contacts of each relay are actuated simultaneously by an actuator (1018, 1088; 1118, 1188), wherein the first sets of switching contacts (1012, 1082; 1112, 1182) of the at least two relays (1010, 1080; 1110, 1180) of a group are connected electrically in parallel and the second sets of switching contacts (1014, 1084; 1114, 1184) of the at least two relays of a group (1000, 1100) are connected electrically in parallel, the first sets of switching contacts (1012, 1082) of a first group (1000) being connected electrically in series with the first sets of switching contacts (1112, 1182) of a second group (1100), the second sets of switching contacts (1014, 1084) of the first group (1000) being connected electrically in series with the second sets (1114, 1184) of switching contacts of the second group (1100), wherein the first sets of switching contacts (1012, 1082) of the first group (1000) are connected to the first input terminal (7a) and the second sets of switching contacts (1014, 1084) of the first group (1000) are connected to the second input terminal (7b), wherein the first sets of switching contacts (1112, 1182) of the second group (1100) being connected to the first output terminal (9a) and the second sets of switching contacts (1114, 1184) of the second group (1100) being connected to the second output terminal (9b); and wherein the monitoring and control system further comprises a controller (900) for controlling the relays of the at least two groups (1000, 1100).. Further, the invention concerns a method for operating a safety switch.