Intrinsically Safe Power Supply Multiplexing with Interlock Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing intrinsically safe (IS) redundant systems do not guarantee that only one input supply is connected to the load during changeover, potentially leading to unsafe conditions where more than one input supply is connected simultaneously.
Innovation Solution
A method and apparatus for multiplexing IS outputs using switching modules with interlock signals to ensure only one input is connected to the output at a time, incorporating a guaranteed minimum disconnection period during switching, and mechanical interlocks to prevent transient combinations, suitable for FISCO systems in hazardous environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant power supply units are installed for reliability, then system reliability is improved, but the risk of simultaneous connection of multiple inputs during changeover increases
Solution Approach 1:
The system performs preliminary disconnection of the first power supply before connecting the second power supply during changeover. The control circuit is configured to disconnect the first intrinsically safe power supply from the output circuit before connecting the second intrinsically safe power supply, ensuring that both supplies are never simultaneously connected to the output circuit. This preliminary action prevents the harmful effect of simultaneous connection while maintaining reliability through redundant power supply units.
2Adaptability or versatility
If switching between power supplies is implemented for redundancy, then availability during maintenance is improved, but the complexity of switching control increases
Solution Approach 1:
A control circuit acts as an intermediary between the redundant power supply units and the output circuit. This control circuit manages the switching operations by receiving control signals and executing the disconnection/connection sequences, thereby simplifying the overall system architecture. The control circuit implements the complex switching logic internally while presenting a simple interface for maintenance operations, allowing hot-swappable redundancy without exposing the complexity of the switching control to the user.
Solution Approach 2:
The patent replaces mechanical switching mechanisms with electronic control circuitry that uses electrical signals to control the switching of power supplies. Instead of mechanical relays or contactors, the system uses a control circuit with control signals to manage the connection and disconnection of intrinsically safe power supplies, reducing mechanical complexity while maintaining the ability to perform hot-swappable maintenance.
3Ease of repair
If hot-swappable redundant power supplies are used, then maintenance ease is improved, but the risk of transient unsafe conditions increases
Solution Approach 1:
The control circuit implements preliminary anti-action by preemptively disconnecting the first power supply before the second power supply is connected during hot-swappable maintenance. This prevents transient unsafe conditions where both supplies might be simultaneously connected. The control circuit monitors the state of power supplies and executes disconnection actions in advance to counteract the potential harmful effect of simultaneous connection, allowing maintenance personnel to easily replace power supplies without creating unsafe transient conditions.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention provides for a method of multiplexing a plurality of intrinsically safe inputs for the purpose of functional redundancy using: a plurality of switching modules connected to an intrinsically safe output; and a plurality of substantially identical inputs from a plurality of intrinsically safe input sources to the plurality of respective switching modules; wherein a plurality of interlock signals between each of the switching modules are employed to permit a maximum of one of the switching modules to be active at any point in time, thereby permitting a maximum of one of the plurality of inputs from the plurality of input sources to be connected to the intrinsically safe output; and further including the step of providing a guaranteed minimum period where no input is connected to the intrinsically safe output during switching to an alternative switching module.