Medical Warming Unit Leakage Current Control
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Solution Overview
Problem
Existing medical fluid warming units for blood and infusion fluids can cause leakage currents to patients due to capacitive coupling between heater elements and fluid paths, violating safety standards and potentially stopping heating during faults, which can harm patients.
Innovation Solution
A medical device with a warming unit that connects a heat transfer element to a ground connection through a resistance element to maintain normal leakage currents below a limit and disconnects from ground if a fault current is sensed, ensuring heating continues while keeping leakage currents within safety limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat transfer element is connected to ground to ensure patient safety, then leakage currents are reduced under normal conditions, but heating may be interrupted during fault conditions
Solution Approach 1:
The ground connection is made dynamic through a switchable connection controlled by a control unit. The connection state (connected or disconnected) changes based on detected fault conditions, allowing the system to adapt between safety-priority and heating-continuity modes rather than maintaining a fixed connection state
Solution Approach 2:
The electrical connection parameter (ground connection status) is changed based on system state. Under normal conditions, the ground connection is active to limit leakage currents. Upon detecting a fault condition, the control unit changes the parameter by disconnecting the ground connection, thereby changing the electrical safety characteristics to maintain heating functionality
2Reliability
If the ground connection is maintained during fault conditions, then patient safety is prioritized, but heating functionality is lost
Solution Approach 1:
The system dynamically adjusts the ground connection status based on operational needs and safety requirements. The control unit monitors system state and switches the ground connection on or off accordingly, creating a dynamic balance between safety and functionality rather than a static compromise
Solution Approach 2:
The control unit continuously monitors the system state and uses this feedback to determine the appropriate ground connection status. When a fault condition is detected, the feedback loop triggers disconnection of the ground connection to preserve heating functionality while maintaining patient safety through other means
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 solution effectively manages leakage currents under normal and fault conditions, ensuring patient safety and compliance with international safety standards while maintaining heating functionality, thus enhancing the reliability and cost-effectiveness of the medical device.
Implementation Method 1
connecting a heat transfer element (22) to a ground connection (33) through a resistance element (34), which keeps a normal condition patient leakage current below a first limit value
Implementation Method 2
at least an electrical heater element (23) connected to a main electrical source (24) providing a mains voltage, at least a heat transfer element (22) in contact or configured to be put in contact with the heated portion
Implementation Method 3
an electrical safety insulation (25) interposed between the electrical heater element (23) and the heat transfer element (22)
Data Source
AI summary
A warming unit (21) coupled or configured to be coupled to a heated portion (19) of a fluid circuit (6, 7, 10, 11, 13, 14, 15; 107) of a medical device (1, 100). The warming unit (21) comprises a leakage current reduction circuit (35) configured to perform the following procedure: connecting a heat transfer element (22) of the warming unit (21) to a ground connection (33) through a resistance element (34), which keeps a normal condition patient leakage current below a first limit value, and disconnecting the heat transfer element (22) from the ground connection (33) if a current indicating that a patient is connected to a mains voltage is sensed through the resistance element (34), in order to keep a fault condition patient leakage current below a second limit value.