Relay Excitation Coil Short-Circuit Safety Switching
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Solution Overview
Problem
Discrete functional safety circuits in automation devices face challenges in monitoring signals and ensuring safety integrity, particularly in two-channel structures required for certain safety levels, where incorrect operation of relay assemblies can lead to security breaches.
Innovation Solution
The circuit arrangement incorporates an excitation coil with a safety switching device that electrically short-circuits the coil in specific states, ensuring the relay is not released during incorrect operation, and includes a return circuit and transistor assembly for controlled deactivation, using readily available and inexpensive components like bipolar transistors to enhance security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If discrete functional safety circuits are used with transistors or FETs to enable relays, then the relay can be turned on directly with input signals, but it becomes difficult to monitor signals and ensure safety integrity
Solution Approach 1:
The patent introduces an intermediary monitoring circuit that interfaces between the discrete functional safety circuit components and the relay assembly. This intermediary circuit enables signal monitoring while maintaining the direct switching capability, resolving the contradiction by adding a mediating layer that provides both monitoring functionality and preserves the original switching operation.
2Reliability
If electrical disconnection is used to release the relay, then the relay releases in case of disconnection, but incorrect operation can still occur and security is compromised
Solution Approach 1:
The patent applies preliminary anti-action by implementing a safety switching device that actively prevents incorrect operation before it can occur. The device monitors the electrical circuit state and actively short-circuits the excitation coil when incorrect operation is detected, counteracting potential harmful effects before they can compromise security.
Solution Approach 2:
The patent converts the potentially harmful short-circuit condition into a beneficial safety mechanism. By deliberately designing the system to short-circuit the excitation coil under specific conditions, the harmful electrical short is transformed into a useful security feature that prevents incorrect relay operation and enhances overall system safety.
3Object-affected harmful factors
If a safety switching device is added to electrically short-circuit the excitation coil, then security is increased, but the device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing the safety switching device to perform multiple functions: it monitors the electrical circuit, detects incorrect operation conditions, and actively short-circuits the excitation coil when needed. This universal approach consolidates multiple safety functions into a single integrated device, reducing overall complexity while maintaining enhanced security.
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 reliably prevents incorrect operation of the relay assembly, increasing security by ensuring the circuit is electrically isolated when necessary and protecting components from damage due to short-circuit currents.
Implementation Method 1
a relay assembly (108) with an excitation coil (118)
Implementation Method 2
an electrical circuit having at least the excitation coil being electrically short-circuited in a first switching state of the safety switching device (112)
Data Source
Figure 1
AI summary
The circuit arrangement (100)has a relay module (108) with an excitation coil (118) and a safety switching unit (112). An electrical circuit (180) is electrically short-circuited with the exciting coil in a first switching state of the safety switching unit. The circuit is electrically separated with the exciting coil in a second switching state of the safety switching unit.