Galvanically Isolated Safety Circuit With Current-Limited Signal Transfer
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Solution Overview
Problem
Conventional safety devices in industrial automation face reliability issues due to the risk of galvanic separation loss caused by overheating and current overloads in transmission units, leading to unintended activation of actuators.
Innovation Solution
Incorporating a current limitation element connected directly to the voltage supply connection of the transmission unit, specifically designed for the highest voltage present, to prevent overheating and ensure galvanic separation is maintained, thereby reducing the risk of short-circuits between logic and load voltage zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission unit is connected directly to the voltage supply connection without a current limitation element, then the transmission unit can operate with sufficient current, but the transmission unit is at risk of overheating and current overload which can cause loss of galvanic separation
Solution Approach 1:
A current limitation element is introduced as an intermediary component between the voltage supply connection and the transmission unit. This mediator limits the current flowing to the transmission unit, preventing overheating and current overload while still allowing sufficient current for normal operation, thus maintaining galvanic separation reliability
Solution Approach 2:
The current limitation element provides beforehand cushioning by pre-limiting the maximum current that can reach the transmission unit. This protective measure is in place before any fault condition occurs, cushioning against potential overheating and current overload scenarios that could compromise galvanic separation
2Reliability
If the transmission unit is supplied from a voltage converter with lower voltage, then the transmission unit operates at lower voltage, but the voltage converter itself can be damaged by overvoltage faults and subsequently cause short-circuit between logic and load voltage zones
Solution Approach 1:
The transmission unit is extracted from the vulnerable voltage converter supply chain and connected directly to the voltage supply connection. This removes the transmission unit from the risk zone where voltage converter damage could cause short-circuits, while the current limitation element ensures direct connection does not create overheating risks
Solution Approach 2:
The voltage supply system is segmented into two independent paths: one path supplies the voltage converter for logic voltage zone components, and another direct path with current limitation supplies the transmission unit. This segmentation isolates the transmission unit from voltage converter faults that could cause short-circuits between logic and load voltage zones
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 design enhances the safety and reliability of the safety device by preventing overheating and maintaining galvanic separation, even in fault conditions, thus ensuring the integrity of the safety device's operation.
Implementation Method 1
the risk of the transmission unit being able to become damaged, for example by way of too high a current subjection and an overheating which is caused by way of this
Data Source
AI summary
A safety device (10, 30, 40, 50), in particular a safety control apparatus and/or a safety diagnosis apparatus, for industrial automation, including a logic voltage zone (4), a load voltage zone (5) which is galvanically separated from the logic voltage zone (4), a transmission unit (6) for transmitting a communication signal between the logic voltage zone (4) and the load voltage zone (5) whilst maintaining the galvanic separation, a first voltage supply connection (7) for providing a first supply voltage (V1) for the logic voltage zone (4) and a first current limitation element (8), wherein the transmission unit (6) is connected on the first voltage supply connection (7) via the first current limitation element (8) and is fed from the first voltage supply connection (7) via the first current limitation element (8).