Sealed Contactor Layout With External Fuse for Arc Protection
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Solution Overview
Problem
Existing contactors for high-current circuits are large, heavy, and expensive, and suffer from arcing damage and explosion risks due to high-energy electric arcs, while smaller contactors cannot withstand large currents effectively.
Innovation Solution
A contactor assembly with internal arc contacts and overcurrent protection outside the housing, featuring an actuator assembly that connects with arc contacts before carry contacts, using an overcurrent protection device outside the housing to manage and dissipate arcs, preventing damage to the carry contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If contactors are designed to withstand large currents, then current handling capability is improved, but device size and weight increase
Solution Approach 1:
The contactor is divided into separate functional components: arc contacts for current interruption, carry contacts for current conduction, and an actuator assembly. This segmentation allows each component to be optimized independently, enabling smaller overall size while maintaining high current handling capability.
Solution Approach 2:
Arc contacts serve as an intermediary element between the power source and carry contacts. They handle the high-energy arc during switching operations, protecting the carry contacts from direct arc exposure and allowing the carry contacts to be smaller and lighter since they don't need to withstand arc damage.
2Power
If arc dissipation members are added to withstand large currents, then current handling capability is improved, but manufacturing cost increases
Solution Approach 1:
The overcurrent protection function is extracted as a separate, replaceable fuse or circuit breaker component positioned outside the main contactor housing. This allows the main contactor body to be manufactured more simply and economically, while the protection function is provided by a standardized, mass-produced component.
Solution Approach 2:
The overcurrent protection device (fuse) is designed as a disposable, low-cost component that can be replaced rather than repaired. This is more economical than designing the entire contactor with built-in arc dissipation members, as fuses are simple, mass-producible components that protect the more expensive contactor body.
3Weight of stationary object
If contacts are made smaller to reduce size, then device weight is reduced, but reliability decreases due to arc damage
Solution Approach 1:
Arc contacts are designed to make contact and establish the electrical pathway before the carry contacts engage. This preliminary action ensures that any arc is established and contained at the arc contacts first, protecting the carry contacts from arc damage before they begin carrying the full load current.
Solution Approach 2:
Arc contacts act as an intermediary that absorbs and contains the arc energy, protecting the smaller, lighter carry contacts from direct arc exposure. This allows the carry contacts to be smaller without sacrificing reliability, as the arc damage is prevented by the arc contacts serving as a protective intermediary.
4Reliability
If integrated overcurrent protection is built into the contactor, then protection reliability is improved, but device complexity and cost increase
Solution Approach 1:
The overcurrent protection function is segmented as a separate module (fuse or circuit breaker) that can be independently selected and replaced. This reduces the complexity of the main contactor design while maintaining reliable protection, as the protection device can be optimized independently from the switching mechanism.
Solution Approach 2:
The external overcurrent protection device serves multiple functions: it protects against overcurrent, provides arc containment, and can be replaced without affecting the contactor itself. This universal approach simplifies the overall system design compared to integrating specialized arc dissipation members into the contactor structure.
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 provides a compact, cost-effective contactor that safely switches high currents, preventing arcing damage and explosion by containing and dissipating arcs, with replaceable overcurrent protection.
Implementation Method 1
An electrical fuse may be provided outside of the sealed contactor assembly. The fuse may be replaceable and/or user replaceable.
Implementation Method 2
As the actuator assembly is moved toward the closed position, the actuator assembly makes an electrical connection with the arc contacts prior to making an electrical connection with the current carry contacts.
Implementation Method 3
The contactors control current flow through the circuit by opening or closing a conductive pathway that extends through the contactor to correspondingly open or close the circuit.
Implementation Method 4
When the contactors change from the closed state to the open state, an electric arc may radiate from the contacts in the contactor when current is interrupted.
Data Source
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AI summary
An embodiment is directed to a contactor assembly (102) which is adapted for switching power to a circuit having a power source. The contactor assembly includes a housing (116, 210) defining an interior compartment (220, 222). Carry contacts (202, 204) and arc contacts (206, 208) are positioned in the interior compartment of the housing. At least one arc contact has an overcurrent protection device (304) positioned outside of the interior compartment of the housing. As an actuator assembly (226) is moved toward the closed position, the actuator assembly makes an electrical connection with the arc contacts prior to making an electrical connection with the current carry contacts, and as the actuator assembly is moved toward the open position, the actuator assembly maintains an electrical connection with the arc contacts after breaking an electrical connection with the current carry contacts, prior to breaking the electrical connection with the arc contacts.