In-Core Instrument Drive Safety Circuit for Cover-Open Power Cutoff
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Solution Overview
Problem
The conventional drive device for in-core neutron instrumentation systems poses risks of operator injury and electric shock during maintenance and inspection due to the ability to power the drive motor even when the cover member is removed, allowing contact with rotating components.
Innovation Solution
A safety circuit is integrated to control the power supply to the drive motor based on the mounted state of the cover member, enabling power only when the cover is securely in place, thereby preventing accidental contact and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cover member is fixed using a snap lock that allows easy removal, then the ease of operation for maintenance and inspection is improved, but the safety of the operator deteriorates due to risk of contact with rotating components
Solution Approach 1:
The safety circuit applies preliminary anti-action by preemptively cutting off power supply to the drive motor when the cover member is removed. The microswitch detects the cover's removed state and opens the circuit before any harmful contact can occur, preventing the harmful effect rather than merely reacting to it.
Solution Approach 2:
The microswitch acts as an intermediary between the cover member's mounting state and the power supply control. It translates the physical state of the cover (mounted or removed) into an electrical signal that controls the safety circuit, mediating the connection between mechanical state and power control.
2Productivity
If the drive motor can operate during maintenance with the cover removed, then the productivity and operational flexibility are improved, but the reliability of safe operation deteriorates
Solution Approach 1:
The safety circuit prevents harmful effects by cutting off power supply in advance when the cover member is in the removed state, before any contact with rotating components can occur. This preliminary action ensures that even if the drive mechanism is accessible, it cannot operate without power.
Solution Approach 2:
The microswitch provides feedback about the cover member's mounting state to the safety circuit. This feedback mechanism ensures that the power supply control is continuously synchronized with the actual physical state of the cover, maintaining safety while allowing operational flexibility when properly covered.
Data Source
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AI summary
A drive device (100) for an in-core neutron instrumentation system includes a safety circuit (10) between a power supply (20) and a drive motor (3). The safety circuit (10) is provided inside the cover member (8), and switches between a conductive state in which power can be supplied to the drive motor (3) and a cut-off state in which power cannot be supplied thereto depending on a mounted state of the cover member (8). The safety circuit (10) is controlled to be in the conductive state in response to a state in which the cover member (8) is mounted on the base member (9), and is controlled to be in the cut-off state in response to a state in which the cover member (8) is not mounted on the base member (9).