DC Relay Magnetic Loop Layout for Short-Circuit Contact Stability
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Solution Overview
Problem
Existing high-voltage DC relays face challenges in maintaining reliable contact and preventing bounce-off due to short-circuit currents, which can lead to arcing failures. The magnetic conductive loop structure used to mitigate these issues is limited by the suction force generated, which can be insufficient to counteract the electromagnetic repulsion force at high fault currents.
Innovation Solution
The DC relay incorporates a design with two static contact leading-out ends, a movable contact piece, and a pushing rod assembly. This design includes a fixed upper yoke, a follow-up upper yoke, and a lower armature, which form two magnetic conductive loops. These loops generate an electromagnetic suction force to keep the movable contacts closed, resisting the electric repulsion force caused by fault currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic conductive loop with upper yoke and lower armature is used to generate electromagnetic suction force, then the anti-short circuit current capability is improved, but the suction force becomes insufficient to counteract electromagnetic repulsion force at high fault currents
Solution Approach 1:
The patent divides the single magnetic conductive loop into two separate magnetic conductive loops: a first magnetic conductive loop (upper yoke 4, lower armature 6) and a second magnetic conductive loop (follow-up upper yoke 5, lower armature 6). This segmentation allows the suction forces from both loops to act simultaneously on the movable contact piece, doubling the total electromagnetic suction force available to counteract the electromagnetic repulsion force at high fault currents, thereby resolving the contradiction between reliability and force magnitude.
2Reliability
If permanent magnets are arranged around contacts for magnetic blowing arc extinction, then arc extinction capability is improved, but Lorentz force causes movable contact piece to move downward resulting in bounce-off
Solution Approach 1:
The patent applies local quality by arranging permanent magnets (first permanent magnet 811, second permanent magnet 812) specifically at the ends of the movable contact piece 2 in the width direction, rather than uniformly around all contacts. This localized arrangement creates a magnetic field concentrated at the contact ends for effective arc extinction, while the symmetrical placement ensures that Lorentz forces on opposite sides balance each other, preventing net downward movement and bounce-off of the movable contact piece.
3Device complexity
If single magnetic conductive loop is used to reduce device complexity, then structure is simpler, but suction force is insufficient to prevent contact bounce-off at high currents
Solution Approach 1:
The patent divides the magnetic conductive loop system into two independent loops: the first magnetic conductive loop (upper yoke 4, lower armature 6) and the second magnetic conductive loop (follow-up upper yoke 5, lower armature 6). Each loop independently generates electromagnetic suction force, and their combined effect provides sufficient total suction force to prevent contact bounce-off at high currents. This segmentation increases reliability while maintaining relatively simple structure by reusing the lower armature 6 in both loops.
Solution Approach 2:
The lower armature 6 serves dual functionality by participating in both the first magnetic conductive loop and the second magnetic conductive loop. This multi-functionality allows the single lower armature to cooperate with both the fixed upper yoke 4 and the movable follow-up upper yoke 5, generating suction forces from both loops simultaneously. This approach increases the total suction force and contact stability without proportionally increasing the number of magnetic components, thus maintaining device complexity at an acceptable level.
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 proposed solution effectively enhances the anti-short circuit current capability of the DC relay, ensuring reliable contact and preventing arcing failures even at high fault currents. The design improves the suction force generated, effectively counteracting the electromagnetic repulsion force and maintaining contact pressure.
Implementation Method 1
the lower armature and the fixed upper yoke and the follow-up upper yoke form two magnetic conductive loops in the width direction of the movable contact piece, so that when a large fault current flows through the movable contact piece, the two magnetic conductive loops generate an electromagnetic suction force
Implementation Method 2
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 3
the energized movable contact piece is subjected to Lorentz force under the magnetic field of the magnetic blowing arc extinction, due to a magnetic circuit layout of the magnetic blowing arc extinction, the movable contact piece is subjected to the Lorentz force to move downward
Data Source
AI summary
A DC relay for anti-short circuit current and arc extinction includes two static contact leading-out ends, a movable contact piece in a straight sheet type, a pushing rod assembly, a fixed upper yoke, a follow-up yoke and a lower armature. The fixed upper yoke is fixed above the movable contact piece, corresponding to a position between the two movable contacts. The follow-up upper yoke is fixed on the pushing rod assembly, above the movable contact piece, corresponding to a position between the two movable contacts. The lower armature is fixed on a bottom end face of the movable contact piece. The fixed upper yoke, the follow-up upper yoke and the lower armature are respectively arranged in a width direction of the movable contact piece, and two magnetic conductive loops are formed in the width direction of the movable contact piece.