PTC Current Limiting Device for Circuit Breaker
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrical protection devices, such as low-caliber circuit breakers, suffer from high total resistance and significant Joule dissipated losses due to their architecture, which includes a magnetic coil and bimetallic strip, leading to inefficiencies in current limiting and fault detection.
Innovation Solution
The use of a current limiting device comprising a stack of Positive Temperature Coefficient (PTC) elements with amplification means and a shunt connected in parallel, which reduces Joule losses and enables efficient fault detection and contact opening with minimal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic coil and bimetallic strip architecture is used for fault detection and actuation, then the circuit breaker can detect overloads and short circuits, but the total resistance increases significantly causing high Joule losses
Solution Approach 1:
The patent merges the fault detection function and current limiting function into a single PTC element. The PTC element simultaneously detects overloads through its resistance change and limits fault current through its positive temperature coefficient characteristics, eliminating the need for separate magnetic coils and bimetallic strips that cause high Joule losses.
Solution Approach 2:
The patent extracts and removes the magnetic coil and bimetallic strip components from the traditional circuit breaker architecture. By taking out these high-resistance components and replacing them with a low-resistance PTC element, the invention significantly reduces total resistance and associated Joule losses while maintaining fault detection capability.
2Loss of energy
If a PTC component is used to replace the bimetallic strip and coil, then the resistance and Joule losses are reduced, but the device requires a simplified design with fewer components
Solution Approach 1:
The PTC element serves multiple functions simultaneously: it acts as the fault detection sensor, the current limiting device, and the actuator that triggers the tripping mechanism. This multi-functionality simplifies the overall device design by consolidating what would traditionally require separate components, thereby reducing device complexity while maintaining energy efficiency.
3Loss of energy
If the PTC component heats up quickly during a short circuit to increase resistance, then the current limitation is effective, but the contacts need to be opened rapidly which requires a responsive triggering mechanism
Solution Approach 1:
The patent introduces a thermal bridge as an intermediary mechanism that translates the thermal expansion of the PTC element into mechanical motion for the tripping mechanism. The thermal bridge amplifies the small dimensional changes in the PTC element during heating, enabling rapid and reliable actuation of the contact opening mechanism in response to fault conditions.
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 significantly reduces Joule losses and allows for rapid and efficient fault current limitation, enhancing the durability of circuit breaker contacts and reducing costs by minimizing material usage and ventilation requirements.
Implementation Method 1
when a short circuit fault occurs, the large short circuit current heats the PTC component very quickly (in a few milliseconds)
Implementation Method 2
said limiting device comprising an element made of a material with a positive temperature coefficient called PTC
Implementation Method 3
the aforementioned triggering means are controlled by the variation in the thickness of the CTP elements during the aforementioned change of state
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
The present invention relates to an electrical protection device A comprising at least one main conductor and, for the or each main conductor, a current limiting device connected in series with said main conductor to limit the current when a current or temperature threshold is exceeded, said limiting device comprising an element made of a material with a positive temperature coefficient said PTC (6 to 9), and being capable of controlling tripping means (d) of the mechanism M for opening the contacts (1,2) of the protection device D, so as to cause the contacts of the device to open when the aforementioned threshold is exceeded causing a change of state of said element between a state of low resistance and a state of high resistance.This device is characterized in that the aforementioned CTP element (6 to 9) includes the aforementioned tripping means (d), in such a way that this element itself performs the functions of limiting the fault current and tripping the contact opening mechanism (1,2).