Electromagnetic Relay Trip Device for Open State Retention

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Solution Overview

Problem

Existing electromagnetic relays face challenges in maintaining the contactor in an open state after an abnormal current is detected, as the driving force of the overcurrent detection coil is released, allowing the contactor to potentially return to a closed state due to magnetic flux attraction.

Innovation Solution

The electromagnetic relay incorporates a trip device with a second excitation coil connected in series to the contactor and a spring that acts on the movable element, ensuring it remains in the open state even after the driving force is released, using the magnetic flux generated by the second coil to counteract the attraction force of the permanent magnet.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the overcurrent detection coil is used to drive the movable element when abnormal current flows, then the contactor can be turned off rapidly, but the contactor may return to closed state when the driving force is released due to permanent magnet attraction

Engineering Contradiction:

Improvespeed of contactor openingVSAvoidreliability of contactor remaining open

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The trip coil is activated in advance to generate magnetic flux that counteracts the permanent magnet's attraction force before the contactor can return to closed state. This preliminary action ensures the movable element stays in open position by pre-establishing the counteracting magnetic field when abnormal current is detected

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The trip coil generates magnetic flux in opposition to the permanent magnet's attraction force. This anti-action prevents the harmful effect of the permanent magnet that would otherwise cause the contactor to return to closed state prematurely, ensuring reliable fault isolation

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If a trip device with second excitation coil is added to maintain open state, then the contactor remains reliably open during abnormal current, but the device complexity increases

Engineering Contradiction:

Improvereliability of contactor remaining openVSAvoidcomplexity of electromagnet device

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The trip coil serves multiple functions: it detects abnormal current conditions, generates counteracting magnetic flux to maintain open state, and works cooperatively with the permanent magnet during normal operation. This multi-functionality reduces the need for separate dedicated components for each function

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The trip device is integrated into the existing electromagnet structure, combining the trip coil with the permanent magnet and movable element assembly. This merging approach allows the additional functionality to be achieved while minimizing structural complexity and component count

Inventive Principle:

Principle #5Merging (Combining)

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 effectively maintains the contactor in the open state during abnormal current conditions, preventing re-closure and ensuring rapid detection and isolation of the electrical path, thus enhancing safety and reliability.

Implementation Method 1

the permanent magnet attractingly holds the movable element

Methodology Applied

Scientific EffectMagnetic flux attraction: Magnetism

Implementation Method 2

the fixed element attracts the first movable element due to a magnetic flux generated by the first excitation coil

Methodology Applied

Scientific EffectElectromagnetic attraction: Electromagnet

Implementation Method 3

using the magnetic flux generated by the second coil to counteract the attraction force of the permanent magnet

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 4

a spring for acting a force on the second movable element in a direction away from the first movable element

Methodology Applied

Scientific EffectElastic force: Spring

Data Source

PatentUS10403461B2Electromagnetic relay

Publication Date: 2019.09.03 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An electromagnetic relay includes an electromagnet device, a contactor, and a trip device turning the contactor into an open state in which the contactor opens when an abnormal current flows. The electromagnet device includes a first excitation coil, a fixed element, first and second movable elements, and a permanent magnet. The contactor includes a fixed contact and a movable contact. In the electromagnetic relay, while the permanent magnet causes the first movable element to attractingly contact the second movable element, the fixed element attracts the first movable element due to a magnetic flux generated by the first excitation coil so as to move the second movable element together with the first movable element from a normal position to an attracted position. In the contactor, the movable contact moves, as the second movable element moves, so as to switch between a closed state in which the movable contact contacts the fixed contact and the open state in which the movable contact is removed from the fixed contact. The contactor is turned into the closed state when the second movable element is located at the attracted position. The trip device includes a second excitation coil connected in series to the contactor and a spring for acting a force on the second movable element in a direction away from the first movable element.