PTC Protection Device with Series Thermal Contact for Residual Current Interruption
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Solution Overview
Problem
Existing protection devices using PTC components fail to effectively interrupt very small currents that can still flow after the PTC component trips, which may not be desirable in electrical circuits with driving elements.
Innovation Solution
A protection device comprising a PTC component and two non-resettable contact components, where the second contact component is connected in series to the PTC component and opens due to heat generated by the tripped PTC component, ensuring complete interruption of current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PTC component is used to protect the circuit, then overcurrent protection is achieved, but very small current still flows through the tripped PTC component
Solution Approach 1:
The protection device is segmented into multiple functional components: a first non-resettable contact component for main overcurrent protection, a PTC component for current limiting, and a second non-resettable contact component for eliminating residual current. Each segment performs a specific protection function, and together they achieve complete current interruption.
Solution Approach 2:
The second non-resettable contact component acts as an intermediary element between the tripped PTC component and the load. It is thermally coupled to the PTC component and uses the heat generated by the tripped PTC to open its contacts, thereby eliminating the residual current that would otherwise flow through the PTC component.
2Reliability
If the second non-resettable contact component is added to interrupt residual current, then complete current interruption is achieved, but device complexity increases
Solution Approach 1:
The second non-resettable contact component is thermally merged with the PTC component through direct contact or close proximity. This thermal coupling allows the second contact component to be actuated by the heat generated by the tripped PTC component, eliminating the need for separate sensing elements or additional power sources.
Solution Approach 2:
The tripped PTC component serves a dual function: it limits the main current and simultaneously generates the heat required to open the second non-resettable contact component. The heat generated by the PTC component during tripping automatically actuates the second contact component, which then eliminates the residual current without requiring external control.
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 ensures that even very small currents are interrupted, preventing undesirable operation and increasing the withstand voltage of the protection device by ensuring the second non-resettable contact component remains open, preventing current flow through the PTC component.
Implementation Method 1
the PTC component is tripped by the excessive current to become a high-temperature and high-resistance state
Implementation Method 2
a contact of the second non-resettable contact component is opened due to heat which is generated by the PTC component
Data Source
AI summary
The present invention provides a protection device which includes a PTC component and a first non-resettable contact component which is connected electrically in parallel to the PTC component. A second non-resettable contact component is connected electrically in series to the PTC component, and when the PTC component is tripped by a current which is diverted by opening the contact of the first non-resettable contact component, the contact of the second non-resettable contact component opens due to heat which is generated by the PTC component.