DC Relay Magnetic Loop Layout for Arc Extinction and Short-Circuit Hold
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Solution Overview
Problem
Existing DC relays face challenges in maintaining reliable contact under high short-circuit currents due to electromagnetic forces, leading to arcing and failure, and arc extinction mechanisms can reduce anti-short circuit capability.
Innovation Solution
A DC relay design featuring a fixed upper yoke, follow-up upper yoke, and lower armature forming magnetic conductive loops to enhance electromagnetic suction force, combined with strategically placed permanent magnets for arc extinction, minimizing Lorentz forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetic blowing arc extinction is used with permanent magnets, then arc extinction capability is improved, but anti-short circuit capability deteriorates due to Lorentz force causing contact bounce
Solution Approach 1:
The patent extracts the permanent magnets for arc extinction from the magnetic circuit path of the short-circuit current. By positioning permanent magnets outside the magnetic conductive loop formed by upper and lower yokes, the arc extinction function is separated from the anti-short circuit magnetic path, eliminating the harmful Lorentz force effect on contacts while maintaining arc extinction capability
Solution Approach 2:
The patent introduces a non-magnetic material as an intermediary between the permanent magnets and the magnetic conductive loop. This intermediary prevents the permanent magnets from interfering with the magnetic circuit used for anti-short circuit protection, allowing both functions to coexist without mutual interference
2Device complexity
If upper yoke is fixed on U-shaped bracket of pushing rod assembly, then structure simplicity is improved, but electromagnetic suction force deteriorates due to gap between upper yoke and lower armature
Solution Approach 1:
The patent makes the upper yoke movable by fixing it on the follow-up pushing rod instead of the U-shaped bracket. This dynamic positioning ensures the upper yoke moves with the pushing rod assembly to maintain minimal gap with the lower armature during contact closure, maximizing electromagnetic suction force while keeping the structure relatively simple
3Force
If upper yoke is fixed on follow-up pushing rod, then electromagnetic suction force is improved, but reliability deteriorates when coil cannot hold iron core under strong electromagnetic suction force from short-circuit rings
Solution Approach 1:
The patent segments the upper yoke into multiple parts (first upper yoke and second upper yoke) that can independently interact with the lower armature. This segmentation distributes the electromagnetic suction force across multiple contact points, preventing any single point from experiencing excessive force that could cause the iron core to be released
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 design significantly improves anti-short circuit capability to 16kA and ensures reliable contact by resisting electric repulsion forces, while eliminating the negative impact of arc extinction magnetic fields on anti-short circuit capability.
Implementation Method 1
when the short-circuit current flows through the movable contact piece, an annular magnetic field is generated around the movable contact piece
Implementation Method 2
when the annular magnetic field acts on the upper yoke and the lower armature, the upper yoke and the lower armature can generate suction force
Implementation Method 3
a permanent magnet is arranged around a contact where the two movable and static contacts are in contact, and a magnetic field formed by the permanent magnet is used to realize the magnetic blowing arc extinction
Implementation Method 4
the energized movable contact piece is subjected to Lorentz force under the magnetic field of the magnetic blowing arc extinction
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A short circuit current-resistant and arc-extinguishing DC relay comprises two stationary contact lead-out ends, a movable spring plate in the form of a flat plate, a push rod assembly, an upper fixed yoke, an upper follower yoke, and a lower armature. The upper fixed yoke is fixed to the push rod assembly and positioned above the movable spring plate in a location corresponding to a location between two movable contacts. The upper follower yoke is fixed to the push rod assembly and positioned above the movable spring plate in a location corresponding to the location between the two movable contacts. The lower armature is fixed to a bottom end surface of the movable spring plate. The upper fixed yoke, the upper follower yoke and the lower armature are respectively arranged in a width direction of the movable spring plate, and form two magnetic conductive loops in the width direction of the movable spring plate. The above arrangement can enhance electromagnetic attraction, thereby achieving a short-circuit current resistance up to the 16kA level for a product.