Electrical Contactor With Movable Arms For High Current
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Solution Overview
Problem
Existing power disconnect contactors face challenges in managing high overload currents, leading to increased contact pressure and reduced switching life, while also experiencing self-heating issues due to solenoid actuation, which complicates the use of cheaper electronic components and increases thermal and structural stresses.
Innovation Solution
The design incorporates a pair of movable arms with aligned opposition, where current flow generates an attractive electromagnetic force, increasing contact pressure during high currents, and a pre-loading mechanism to reduce solenoid actuation requirements, along with a wedge-shaped actuator for opening and closing contacts, allowing for a compact and symmetrical construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple blade and contact arrangements are employed in parallel to share load current, then electrical resistance is reduced and self-heating is minimized, but device complexity increases
Solution Approach 1:
The contactor is divided into multiple parallel blade and contact arrangements (first, second, third, and fourth arrangements), each handling a portion of the total load current. This segmentation reduces the current burden on each individual contact path, thereby reducing electrical resistance and self-heating effects while distributing the thermal load across multiple independent segments.
Solution Approach 2:
Multiple parallel blade and contact arrangements are combined within a single contactor housing, with all arrangements working simultaneously to handle the total load current. The merging of these multiple paths creates an equivalent parallel electrical circuit that reduces overall resistance and distributes heat generation, achieving thermal management through structural integration.
2Reliability
If solenoid actuators are continuously energised for contact closure, then contact reliability is improved, but coil self-heating increases
Solution Approach 1:
Instead of continuous energization, the solenoid actuator is designed to operate in periodic pulses. The solenoid is energized only during the brief moment needed to close the contacts, then de-energized while maintaining contact closure through the mechanical force already applied. This periodic action maintains contact reliability while dramatically reducing coil self-heating by limiting active energization to minimal necessary intervals.
3Power
If heavy duty terminals and fixed contacts are used, then current carrying capacity is improved, but temperature rise due to voltage drops increases
Solution Approach 1:
The current path is segmented into multiple parallel terminal and contact arrangements, distributing the total current across four separate paths. Each heavy duty terminal and fixed contact arrangement handles only a portion of the total current, reducing the voltage drop (V=IR) and corresponding heat generation (P=I²R) in each individual path, thereby reducing overall temperature rise while maintaining high current carrying capacity.
4Temperature
If magnet latching types are used instead of solenoid actuators, then coil self-heating is reduced, but contact pressure may be insufficient for low resistance switch path
Solution Approach 1:
The contactor employs multiple parallel blade and contact arrangements where each arrangement contributes to the total contact pressure. By distributing the load across multiple contact points, the required pressure per individual contact is reduced, allowing magnet latching types to provide sufficient total contact pressure without excessive coil heating. The segmented structure enables adequate force distribution that single-contact designs cannot achieve.
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 solution provides a low on-resistance contactor with reduced solenoid force requirements, increased contact pressure during overloads, and minimized self-heating, enhancing reliability and operational performance under demanding overload conditions.
Implementation Method 1
current flowing through the movable arms produces a force that urges the movable arms towards each other thereby increasing the force between the fixed and movable contacts
Data Source
AI summary
In an electrical contactor a first terminal (5) is connected to a pair of contacts (3, 4) on opposite faces of a fixed conductive member (2). A second terminal (6) is connected to a pair of movable arms (7, 8) of electrically conductive material carrying movable contacts (9, 10) at an end remote from the connection to the second terminal (6). The movable arms (7, 8) are arranged in aligned opposition to each other and such that their remote ends are on either side of the fixed member (2) with the movable contacts (9, 10) aligned with the fixed contacts (3, 4). The arrangement of the fixed member (2) and movable arms (7, 8) is such that when the contacts are closed current flowing through the movable arms produces a force that urges the movable arms towards each other thereby increasing the force between the fixed and movable contacts. In such a contactor overload currents cause the contact force to increase due to the attractive electromagnetic force produced between the arms (7, 8) by currents flowing in the same direction in the arms (7, 8).