Thermistor Device With Offset Posts For Arcing Control
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Solution Overview
Problem
Conventional PTC thermistor devices in refrigeration compressors fail to adequately prevent overheating and electrical arcing due to fractured thermistor rubble remaining in electrical contact, leading to inefficient failure modes.
Innovation Solution
The design incorporates elastic supports and offset posts that apply dynamic forces to minimize electrical contact after failure, with features like cantilever springs and fusible links to distribute rubble away from contacts, reducing arcing and overheating by using offset posts and resilient supports to manage the distribution of fractured thermistor fragments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermistor devices use spring contacts and non-conductive support posts to maintain contact throughout normal life, then the thermistor remains electrically connected during operation, but fractured portions remain in electrical contact causing arcing and overheating upon failure
Solution Approach 1:
The device is segmented into multiple contact points (first and second spring contacts on one side, third spring contact on the other side) arranged at different positions. This segmentation ensures that when the thermistor fractures, not all contact points will simultaneously maintain electrical connection, thereby reducing the likelihood of sustained arcing and overheating while maintaining reliable electrical connection during normal operation.
2Strength
If the thermistor is placed in tension and compression on opposing sides with forces reversed near the other end, then the thermistor is mechanically supported, but under some circumstances fractured portions remain in electrical contact causing arcing
Solution Approach 1:
The spring contacts are positioned asymmetrically rather than symmetrically on the thermistor. The first and second spring contacts are located at different positions on one side, while the third spring contact is positioned on the other side at a different relative location. This asymmetric arrangement ensures that mechanical forces are distributed unevenly, causing fractured portions to be pushed away from electrical contacts and reducing arcing potential while maintaining adequate mechanical support.
3Temperature
If materials in intimate contact with the thermistor electrodes have higher relative temperature index, then the materials can withstand thermal stress, but the device cost increases
Solution Approach 1:
Non-conductive support posts are introduced as intermediary elements between the spring contacts and the thermistor electrodes. These support posts provide mechanical support and electrical isolation, allowing the use of lower temperature index materials for the spring contacts themselves while still protecting against thermal stress through the intermediary support structure. This reduces overall device cost while maintaining temperature resistance.
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 configuration effectively minimizes electrical arcing and overheating by ensuring that fractured thermistor fragments are directed away from conductive contacts, enhancing the reliability and reducing the risk of thermal runaway and electrical arcing during failure.
Implementation Method 1
a first elastic support including a first contact section in contact with the first electrode; and a second elastic support including a second contact section in contact with the first electrode
Implementation Method 2
a pair of offset posts disposed on the same side of the electronic element as the third support and each having an end with a tip, and each tip end is closer to an axis, through the centroid of the electronic element and approximately perpendicular to the electronic element, than the first and second contact sections
Data Source
AI summary
A thermistor device includes include supports, contacts and offset posts configured to assist the fracturing of failed thermistor “pills” and to distribute the fragments of the fractured pills into compartment away from electrically conductive contacts in order to minimize arcing and overheating.