Arc Interruption Layout Using External Magnet and Attraction Rod
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Solution Overview
Problem
Conventional switching devices with permanent magnets face reliability issues during arc interruption due to reversed current direction, as the magnetic drive action is less effective and the magnetic field exerts forces in unexpected directions, leading to increased device size and failure risks.
Innovation Solution
A switching device with a fixed and movable contact, a magnet generating a magnetic field, and an attraction rod with one end near the arc generation region and the other end contacting the magnet's pole surface, where the magnet is positioned outside the arc generation region, allowing the arc to be driven along the attraction rod's lateral surface for efficient cooling and reliable interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnet is mounted in the arc-extinguishing chamber to generate magnetic field for arc interruption, then the arc can be extended and interrupted, but when the energizing direction is reversed, the drive direction of the arc is reversed and reliability of interruption is degraded
Solution Approach 1:
The magnet is inverted from its conventional position inside the arc-extinguishing chamber to a position outside the arc generation region. This inversion allows the magnetic field to act on the arc from a different spatial relationship, enabling the arc to be driven along the attraction rod's lateral surface regardless of current direction, thus resolving the reliability issue when energizing direction is reversed
Solution Approach 2:
An attraction rod is introduced as an intermediary component between the magnet and the arc. The attraction rod serves as a magnetic conductor that guides the magnetic field from the magnet to the arc generation region, enabling controlled arc extension along its lateral surface and ensuring consistent arc drive direction even when current direction reverses
2Reliability
If the arc-extinguishing space is increased to allow interruption when arc is driven in reverse direction, then interruption reliability improves, but the device size is enlarged
Solution Approach 1:
The arc extension path is changed from a linear extension in one dimension to a controlled path along the lateral surface of the attraction rod in another dimension. This dimensional change allows the arc to be effectively extended and cooled without requiring a larger arc-extinguishing space, thus maintaining compact device size while ensuring reliable interruption
3Reliability
If the magnetic pole surface of the permanent magnet is made larger to interlink magnetic lines in uniform direction, then Lorentz force can be applied correctly, but the configuration becomes high-cost and arrangement space is difficult to secure
Solution Approach 1:
The attraction rod acts as a magnetic intermediary that concentrates and guides the magnetic field lines from the magnet's pole surface. This allows a smaller magnet with a smaller pole surface to effectively generate uniform magnetic field lines where needed, eliminating the requirement for a large magnet while maintaining reliable Lorentz force application
Solution Approach 2:
The magnetic field is concentrated locally at the attraction rod's lateral surface where it is most needed for arc control. The attraction rod creates a localized region of high magnetic field density along its surface, ensuring effective Lorentz force application on the arc without requiring the entire magnet surface to be large
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 reliable arc interruption regardless of current direction, maintaining high reliability and reducing device size by effectively extending and cooling the arc along the attraction rod, even with a small magnet, while preventing arc movement between different energizing directions.
Implementation Method 1
a magnet that generates a magnetic field for extending an arc generated between the fixed contact and the movable contact
Implementation Method 2
a magnet that generates a magnetic field for extending an arc
Implementation Method 3
allowing the arc to be driven along the attraction rod's lateral surface for efficient cooling
Data Source
Figure 1
Figure 2
Figure 3A~3E
AI summary
A switching device that can secure reliability of interruption is obtained. A switching device (100) includes: a magnet (4) that generates a magnetic field for extending an arc generated between a fixed contact (1) and a movable contact (2) when a fixed contact point (1a) and a movable contact point (2a) are opened; a magnetic body (3), one end of which is arranged in the vicinity of an arc generation region (20) between the fixed contact (1) and the movable contact (2), and the other end of which is arranged in a manner to contact one magnetic pole surface of the magnet (4); and an insulation cover (3c) that protects the magnet (4) and the magnetic body (3) and that partitions arc extension spaces (21) where energizing directions of the arc differ. The magnet (4) is arranged in a region other than the arc generation region (20).