Metal Shell for Electrical Switching Device with Return Current Cooling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing metal casings for electrical power switching devices experience heating issues due to return currents, which can exceed safe operating temperatures, and current solutions complicate the structure and increase integration costs.
Innovation Solution
A double-walled metal casing design where the return current passes through an outer wall, promoting natural convection cooling and reducing heat transfer to the casing body by routing the current through slots and external walls with higher electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the return current flows through the casing wall, then the magnetic field is reduced and corrosion is limited, but the casing temperature increases due to Joule heating
Solution Approach 1:
The casing wall is segmented into an inner wall and an outer wall separated by an air gap. The return current is directed to flow through the outer wall, which has higher electrical resistance, while the inner wall is protected from excessive current flow. This segmentation allows the current path to be divided between two walls, reducing the heating effect on any single wall while maintaining the return current function.
Solution Approach 2:
The air gap between the inner and outer walls acts as an intermediary that thermally isolates the inner wall from the outer wall. This air gap prevents direct heat transfer from the outer wall (through which the return current flows) to the inner wall and the internal space, thereby reducing the temperature increase in the casing body while allowing the return current to flow through the outer wall.
2Temperature
If cooling mechanisms are added to reduce casing temperature, then the temperature control is improved, but the structural complexity and integration cost increase
Solution Approach 1:
The air gap between the inner and outer walls provides passive thermal insulation that automatically reduces heat transfer without requiring active cooling systems. The natural convection of air in the gap and the thermal resistance of the air layer itself provide cooling functionality, eliminating the need for additional fans, pumps, or complex active thermal management systems.
Solution Approach 2:
The outer wall is designed to serve dual functions: it provides the structural enclosure and simultaneously acts as the current-carrying path for the return current. By merging the structural function with the electrical function in the outer wall, the patent eliminates the need for separate cooling mechanisms while still achieving temperature control through the air gap insulation.
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 design effectively cools the casing by redirecting the return current through external walls, reducing the casing's temperature and integrating cooling mechanisms without increasing structural complexity, thus maintaining the circuit breaker's temperature below 105°C while outside temperatures are at 40°C.
Implementation Method 1
this return current heats the enclosure by Joule effect
Implementation Method 2
The double wall is thus the seat of an air flow established by natural convection to cool the outer wall and the sidewall
Implementation Method 3
the double wall formed by the sidewall with the external wall which runs the passage of the return current to the outside in the outer wall, so that it does not heat up the casing body
Data Source
Figure 1~4
AI summary
The invention relates to a metallic enclosure (1) for a switching device such as a circuit breaker (2) intended to be connected to two conductors (3, 4) in a metallic sheath (6, 7) for the purpose of carrying a nominal current, this enclosure (1) being traversed by a return current. This enclosure (1) comprises: - an enclosure body (11) including at least one lateral side (14, 16) provided with a device (19, 21) opposing the passage of the return current; - for each side (14, 16) provided with a device, an external wall (24, 26) parallel to the side and spaced away from it, while being connected to the enclosure body (11) upstream and downstream of the device (19, 21) with respect to the direction of the return current. The outer wall (24, 26) offers less electrical resistance to the return current than the side (14, 16) with its artifice (19, 21).